How to assess the quality of color reference cards

Abstract

1. A method for assessing the quality of a color reference card (110), the color reference card (110) comprising a plurality of color reference fields (112) having known reference color values, the method comprising: i. capturing at least one image of at least a portion of a color reference card (110) by using at least one camera (130) of at least one mobile device (128); ii. determining measured reference color values ​​for at least some of the color reference fields (112) from the image; iii. determining a relationship between at least some of the measured reference color values ​​and corresponding known reference color values; iv. deriving at least one quality information item related to the quality of the color reference card (110) by using the relationship of step iii. Additionally, a method for determining the concentration of an analyte in a body fluid, a mobile device (128), a kit (126), a computer program and a computer readable storage medium are disclosed.

Description

Technical Field

[0001] Technical Field The present invention relates to a method for evaluating the quality of a color reference card and a method for determining the concentration of an analyte in a body fluid. The present invention further relates to a mobile device having a camera, a kit comprising the mobile device and a color reference card, a computer program, and a computer-readable storage medium. The method and apparatus, as well as the computer program and computer-readable storage medium, can be specifically used for medical diagnosis, for example, for quantitatively and / or qualitatively detecting one or more analytes in one or more body fluids, such as detecting blood glucose in blood and / or interstitial fluid. However, other application fields of the present invention are possible.

Background Art

[0002] Background Art In the field of medical diagnosis, it is often necessary to detect one or more analytes from a sample of a body fluid, such as blood, interstitial fluid, urine, saliva, or other types of body fluids. Examples of analytes to be detected are glucose, triglycerides, lactate, cholesterol, or other types of analytes normally present in these body fluids. Depending on the concentration and / or presence of the analyte, appropriate treatment can be selected if necessary. Without limiting the scope, the present invention can be specifically described with regard to blood glucose measurement. However, it should be noted that the present invention can also be used for other types of analytical measurements using test elements.

[0003] Generally, devices and methods known to those skilled in the art utilize test elements containing one or more test chemicals, which can perform one or more detectable detection reactions, such as optically detectable detection reactions, in the presence of the analyte to be detected. Regarding the test chemicals contained in the test elements, for example, reference can be made to J. Hoenes et al.: The Technology Behind Glucose Meters: Test Strips, Diabetes Technology & Therapeutics, Volume 10, Supplement 1, 2008, S-10 to S-26. Other types of test chemicals are possible and can be used to practice the present invention.

[0004] In analytical measurements, particularly those based on chromogenic reactions, one technical challenge lies in the evaluation of color changes resulting from the detection reaction. In addition to using dedicated analytical devices such as handheld blood glucose meters, the use of commonly available electronic devices such as smartphones and portable computers or other mobile devices has become increasingly popular in recent years. Therefore, the cameras included in these mobile devices can be used to measure color changes in the detection reaction. Generally, commercially available products utilize color standards for photometry measurements, for example, to compensate for different lighting conditions during measurement. One or more images of a color standard having a color standard field with known reference color values can be captured by using the camera of the mobile device. Conversion algorithms can be determined by associating the measured reference color values with the known reference color values.

[0005] For example, U.S. Patent Application Publication No. 2019 / 0137405 describes a system in the field of monitoring air quality, more specifically, in the field of identifying the presence of gaseous chemical contaminants such as volatile organic compounds in a sealed environment. The system includes a substrate, a gaseous chemical contaminant sensor, and at least one colorimetric analysis marker of a predetermined color disposed on the substrate.

[0006] U.S. Patent Application Publication No. 2012 / 0189509 discloses a method for automatically analyzing a test strip, including steps of providing a test strip unit having at least a reaction region and an image calibration region, capturing an image of the test strip unit, analyzing the image to obtain a first image signal of the image calibration region and a second image signal of the reaction region, comparing the first image signal with a standard signal to obtain an image signal calibration parameter, calibrating the second image signal by applying the image signal calibration parameter to obtain a third image signal, and comparing the third image signal with data in a database to obtain a corresponding parameter value. Here, a method for automatically analyzing a test strip is also provided.

[0007] International Publication No. WO 2019 / 162496 pamphlet describes a method, computer program, and system for calibrating and using a camera to detect an analyte in a sample. The calibration method for calibrating a camera for detecting an analyte in a sample includes: a. providing a set of color coordinate systems including a plurality of different color coordinate systems configured to describe the color of an object; b. providing a set of test samples having known concentrations of the analyte; c. applying the test samples to a set of test elements, each test element having at least one test field including at least one test chemical configured to perform an optically detectable detection reaction with the analyte, thereby forming at least one colored test field for each of the test samples; d. acquiring an image of the colored test areas by using the camera; e. forming a set of test samples and a set of color coordinates of the color coordinate systems by generating the color coordinates of the image of the colored test fields by using the color coordinate systems of the set of color coordinate systems; f. providing a set of encoding functions, the set of encoding functions including a plurality of encoding functions for converting the color coordinates of the test fields into the corresponding concentrations of the analyte in the sample; g. converting the set of color coordinates generated in step e into a set of measured concentrations by using the set of encoding functions; h. comparing the set of measured concentrations with the known concentrations of the set of test samples and determining the best-matching color coordinate system of the set of color coordinate systems and the best-matching encoding function of the set of encoding functions with which the set of measured concentrations best matches the known concentrations.

[0008] Despite these advantages realized by these known methods and apparatuses, various technical challenges remain. Specifically, in order to avoid adverse effects on the performance of analytical measurements due to fatigue of color standards, etc., the color standards may need to be replaced periodically. As a precaution, the color standards may be replaced at short time intervals regardless of the actual deterioration of the color standards. Furthermore, the reliability of the color standards and the derived color correction may not need to be verified before or during application. For example, damaged color standards, such as those damaged by scratches or other mechanical effects, may result in poor color correction of the captured images. Therefore, when determining the concentration of the analyte based on the color reaction, if color correction failure occurs, there is a risk that the analytical measurement will be inaccurate.

[0009] Problems to be Solved Therefore, it is desirable to provide an apparatus and method that at least partially address the above-described problems. Specifically, it is desirable to provide an apparatus and method that enable a user-friendly mobile-based determination of the concentration of at least one analyte in a body fluid while ensuring high accuracy and reliability of analytical measurements. Summary of the Invention

[0010] Summary This problem is addressed by a method for evaluating the quality of a color reference card and a method for determining the concentration of an analyte in a body fluid. Furthermore, it is addressed by a mobile device having a camera with the features of the independent claims, by a kit comprising the mobile device and a color reference card, by a computer program, and by a computer-readable storage medium. Advantageous embodiments that can be implemented in a single manner or in any arbitrary combination are described in the dependent claims.

[0011] As used hereinafter, the terms "have", "comprise", "include" or any grammatical variations thereof are used inclusively. Thus, these terms may refer to both situations where there are no additional features in the entity being described in this context in addition to the features introduced by these terms, and situations where there are one or more additional features. By way of example, the expressions "A has B", "A comprises B" and "A includes B" all refer to both situations where there are no other elements in A besides B (i.e., the situation where A consists solely and exclusively of B), and situations where there are one or more additional elements in entity A, such as element C, elements C and D, and even further elements.

[0012] Furthermore, it should be noted that terms such as "at least one", "one or more" or similar expressions indicating that a feature or element can be present one or more times are usually only used once when introducing each respective feature or element. In the following, in most cases, when referring to each respective feature or element, the expressions "at least one" or "one or more" are not repeated, despite the fact that each respective feature or element can be present one or more times. Additionally, the term "at least some" as used herein is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to "one or more" items introduced by this term, specifically two or more of the said items.

[0013] Furthermore, when used hereinafter, the terms "preferably", "more preferably", "in particular", "more specifically", "specifically", or "even more specifically", or similar terms are used with respect to any feature without limiting the possibility of alternatives. Thus, the features introduced by these terms are any features and are not intended to limit the claims in any way. The present invention may be practiced by using alternative features, as will be recognized by those skilled in the art. Similarly, features introduced by "in an embodiment of the present invention" or similar expressions are any features without any limitation regarding alternative embodiments of the present invention, without any limitation regarding the scope of the present invention, and are intended to be any features without any limitation regarding the possibility of combining the features introduced in such a way with any other optional or non-optional features of the present invention.

[0014] In a first aspect of the present invention, a method for evaluating the quality of a color reference card is disclosed, the color reference card including a plurality of color reference fields having known reference color values. The method includes the following steps, which may be performed, by way of example, in a given order. However, it should be noted that different orders may generally be possible. Furthermore, one or more of the method steps may be performed only once or repeatedly. Furthermore, two or more of the method steps may be performed simultaneously or overlapping in time. The method may include additional method steps not described.

[0015] The method comprises i. capturing at least one image of at least a part of the color reference card by using at least one camera of at least one mobile device; and ii. determining measured reference color values for at least some of the color reference fields from the image, i.e., for one or more of the color reference fields, specifically for at least two of the color reference fields; iii. determining the relationship between at least some of the measured reference color values, i.e., one or more of the measured reference color values, specifically at least two of the measured reference color values, and the corresponding known reference color values; iv. deriving at least one quality information item regarding the quality of the color reference card by using the relationships of step iii., and including.

[0016] As used herein, the term "evaluating the quality of a color reference card" is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. This term can specifically, but not limited to, refer to a process of quantitatively and / or qualitatively evaluating the quality of the whole or part of a color reference card, such as determining at least one quality information item for certifying the quality of the color reference card, and / or quantifying the quality of the color reference card or a part thereof, such as at least one color reference field or one or more color reference fields among a plurality of color reference fields of the color reference card. The quality information item may, for example, be a binary value indicating sufficient quality or insufficient quality, or may include it. Additionally or alternatively, the quality information item may be or may include at least one numerical value characterizing the degree of quality of the color reference card, such as a predetermined quality measure. As used herein, the term "quality of a color reference card" can specifically refer to whether the color reference card can be used in a method for determining the concentration of an analyte in a body fluid, and / or the state of the color reference card indicating the degree of fitness or reliability of the color reference card used in a method for determining the concentration of an analyte in a body fluid. The latter can, as outlined above, for example, indicate a reliability or another numerical value indicating the degree of fitness or reliability of the color reference card for use in a method for determining the concentration of an analyte in a body fluid. Hereinafter, possible details of a method for determining the concentration of an analyte in a body fluid will be described. The result of the evaluation of the quality of the color reference card may, as described above, be or may include at least one quality information item regarding the quality of the color reference card. Therefore, the state of the color reference card can be derived using at least one quality information item regarding the color reference card. Furthermore, the result of the evaluation of the quality of the reference card can also include a plurality of quality information regarding the quality of the color reference fields included in the color reference card.Thus, the evaluation can also result in the permission of color reference fields having high quality and / or the exclusion of color reference fields having low quality for determining the relationship in step iii.

[0017] As used herein, the term "color reference card" is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art and should not be limited to a special or customized meaning. This term can specifically refer to, but is not limited to, any item having at least one color reference field having known color or optical properties, such as having one or more colored fields having known color coordinates, disposed on, within, or on at least one surface. By way of example, a color reference card can be a flat card comprising at least one substrate having at least one color reference field having known color coordinates disposed on and / or within at least one surface. The substrate can specifically have a flat surface on which the color reference field is disposed. By way of example, the substrate can be one or more of a paper substrate, a cardboard substrate, a plastic substrate, a ceramic substrate, or a metal substrate, or can include them. A laminated substrate is also possible. The substrate can be, by way of example, sheet-like or flexible. However, it should be noted that the substrate can also be implemented in an article of use such as a medical consumable such as a wall of a box, a vial, a container, a test strip. Thus, the color reference card can also be fully or partially integrated into an optical test strip, as described in more detail below. Thus, at least one image of at least a portion of the color reference card can fully or partially include at least one image of at least a portion of an optical test strip having at least one reagent test area.

[0018] Furthermore, the color reference card may comprise at least one marker. The at least one marker may be, for example, a designator that specifies details of the color reference card, such as a reference color value, by using at least one of a label, a barcode, or a QR code (registered trademark); an identifier for identifying the color reference card and / or at least one of the types of the color reference card, such as at least one of a reference mark, an ArUco code, etc., and / or at least one of position markers and / or orientation markers, or may include them. Specifically, the at least one marker may be arranged at at least one corner of the color reference card. Accordingly, the mobile device may be configured to detect and / or read the marker, specifically, by optically detecting the marker on at least one image captured in step i. and / or optionally obtaining information such as information regarding the type, characteristics, or orientation of the color reference card from the marker.

[0019] As used herein, the term "color reference field" is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to any item having known optical properties such as known reference color values. Specifically, the color reference field included in the color reference card may be a two-dimensional structure such as a rectangle, square, polygon, circle, and / or ellipse having a uniform color value. The color value of the color reference field may specifically be one or more of predetermined, known, or determinable ones. The color reference field may specifically be constituted by and / or disposed within the surface of the color reference card such that at least one color reference field is visible in the captured image in step i. Further, the color reference field may have a color value within a subspace of a color coordinate system corresponding to the color space of the color development reaction in the reagent test area. The color reference field of the color reference card may specifically be arranged in a regular pattern on the surface of the color reference card, such as a rectangular pattern such as a rectangular matrix pattern. The pattern arrangement can specifically enable the identification of the color reference field, such as by searching for a predetermined distance in the x direction and / or y direction from one or more of the markers.

[0020] As used herein, the term "color value" is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art, and should not be limited to a special or customized meaning. Specifically, but not limited to, this term can refer to a numerical representation of the color of a pixel, object, etc. Specifically, the color value may be, or may include, at least one color coordinate in a color coordinate system. As used herein, the term "color coordinate system" is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art, and should not be limited to a special or customized meaning. Specifically, but not limited to, this term can refer to any coordinate system that can mathematically or physically characterize the color of an object, such as the color of a test field or the color of an image recorded by a camera. Various color coordinate systems are generally known to those of ordinary skill in the art, such as the color coordinate system defined by the CIE. Color coordinates can span or define a color space, for example, by defining three or four basis vectors as a whole. For example, the color value can include R, G, B color coordinates. Therefore, the color value can be a color triple having R, G, B color coordinates. Color coordinates in other color coordinate systems, such as the color coordinate system defined by the CIE, are also achievable.

[0021] As used herein, the term "known reference color value" is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, but not limited to, this term can refer to a predetermined, actual, or true color value of a color reference field. Specifically, a known reference color value can include at least three color coordinates, such as at least one color coordinate for each of the R, G, and B colors. The known reference color values for each color reference field may be stored in the data storage device of the mobile device, for example, by a look-up table, register, database, etc. The known reference color values may be determined by measuring each color value, specifically, by measuring the color value in a controlled laboratory environment, such as using a spectrometer. The measurement of the color reference field using a spectrometer can define each known reference color value.

[0022] Furthermore, the known reference color values of one or more second color reference fields may also be determined from the known reference color values of the first color reference field. Specifically, a predetermined and / or known relationship can associate the known reference color values of the first color reference field with the known reference color values of the second reference field. Thus, a color reference card may comprise color reference fields having known reference color values, and the known reference color values may be related to each other. For example, the second color reference field can have a known reference color value that includes at least one color coordinate, such as one of the R, G, B color coordinates, that is 10% higher than at least one of the color coordinates included in the known reference color values of the first color reference field. Furthermore, the third color reference field can have a known reference color value that includes at least one color coordinate, such as one of the R, G, B color coordinates, that is 20% higher than at least one of the color coordinates included in the known reference color values of the first color reference field. Thus, the known reference color values of the first color reference field may be known and may be further used to determine the known reference color values of one or more second color reference fields.

[0023] As outlined above, step i. involves capturing at least one image of at least a portion of the color reference card by using the camera of the mobile device. The term "mobile device" as used herein is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art and should not be limited to a special or customized meaning. This term can specifically, but not exclusively, refer to portable electronic devices, and more specifically, portable communication devices such as mobile phones or smartphones. Additionally or alternatively, as further outlined in more detail below, the mobile device can also refer to a tablet computer or another type of portable computer having at least one camera.

[0024] The term "camera" as used herein is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art and should not be limited to a special or customized meaning. The term can specifically, but not exclusively, refer to a device having at least one image sensor configured to record or image spatially resolved one-dimensional, two-dimensional, or three-dimensional optical data or information. By way of example, a camera can include at least one camera chip such as at least one CCD chip and / or at least one CMOS chip configured to record an image. As used herein, the term "image" can specifically, but not exclusively, relate to data recorded by using a camera, such as a plurality of electronic readings from an image sensor such as the pixels of a camera chip.

[0025] In addition to at least one camera chip or imaging chip, the camera can include one or more optical elements, such as additional elements like one or more lenses. By way of example, the camera can be a fixed-focus camera having at least one lens that is fixedly adjusted with respect to the camera. However, alternatively, the camera can also include one or more variable lenses that can be adjusted automatically or manually. The present invention is specifically applicable to cameras commonly used in mobile applications, such as notebook computers, tablets, or specifically mobile phones such as smartphones. Thus, specifically, the camera can be part of a mobile device that includes one or more data processing devices, such as one or more data processors, in addition to at least one camera. However, other cameras can also be used.

[0026] Specifically, the camera can be a color camera. Thus, for each pixel and the like, color information such as color values of the three colors R, G, B can be provided or generated. It is also possible to implement more color values, such as four color values for each pixel, for example R, G, G, B, etc. Color cameras are generally known to those skilled in the art. Thus, by way of example, the camera chip can be composed of three or more different color sensors, such as one pixel for red (R), one pixel for green (G), and one pixel for blue (B), such color recording pixels. For each pixel such as R, G, B, depending on the intensity of each color, the value can be recorded by a pixel such as a digital value in the range from 0 to 255. By way of example, instead of using a color triple such as R, G, B, four parts such as R, G, G, B can be used. The color sensitivity of the pixel can be generated by a color filter or by the appropriate inherent sensitivity of the sensor element used in the camera pixel. These techniques are generally known to those skilled in the art.

[0027] As used herein, the term "capturing at least one image" is a broad term and should be given its ordinary and customary meaning to one of ordinary skill in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to one or more of imaging, image recording, image acquisition, and image capture. The term "capturing at least one image" can include capturing a single image and / or multiple images such as a series of images. For example, capturing an image can include continuously recording a series of images such as a video or movie. Capturing at least one image can be initiated by a user action or can be automatically initiated, for example, when the presence of at least one object within the field of view of the camera and / or within a predetermined sector of the field of view is automatically detected. These automatic image acquisition techniques are known, for example, in the field of automatic barcode readers such as automatic barcode reading applications. Image capture can be performed, by way of example, by a camera acquiring a stream or "live stream" of images, and one or more of the images can be stored and used as at least one first image and / or at least one second image, respectively, automatically or by user interaction such as pressing a button. Image acquisition may be supported by a processor of the mobile device, and image storage may be performed within a data storage device of the mobile device.

[0028] As outlined above, step ii. involves determining the reference color values measured for at least some of the color reference fields from the image. The term "measured reference color value" as used herein is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to color values determined from the image captured in step i. by measurement, specifically by using the camera of the mobile device, and more specifically. Thus, the measured color value may be, or may include, at least one color value of at least one color reference field measured by using the camera of the mobile device and optionally at least one processor of the mobile device for evaluating the image. For example, a color reference field arranged on a color reference card may be identified on the image captured in step i. by one or more of a computer vision process and / or image analysis, and the color value of the color reference field may be determined by at least one color sensor included in the camera of the mobile device. Specifically, the camera of the mobile device may comprise at least three color sensors, such as a pixelated color sensor or color pixels, for example at least one color sensor for R, G, B colors, and thus the measured color value may comprise at least three color coordinates that can be derived from the sensor signals of the color sensors, more specifically at least one color coordinate for each of the R, G, B colors.

[0029] Furthermore, the method includes, in step iii., determining the relationship between the measured reference color values and the corresponding known reference color values. As used herein, the term "relationship" is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to a predetermined or determinable conversion between color information derived from an image, such as measured reference color values, and corresponding known color information, such as known reference color values. Specifically, the relationship may be a mathematical conversion or may include a mathematical conversion. Thus, the term "relationship" specifically, without limitation, refers to a predetermined or determinable conversion algorithm for converting at least one piece of color information derived from an image, also referred to as a "measurement item of color information", such as at least one measured reference color value, into one or more items of known color information, particularly at least one item of "real world", "reality", "predicted", or "true" color information, such as known reference color values. The relationship may specifically be a convertible or reversible conversion or algorithm, or may include it. Thus, hereinafter, no distinction is made between the relationship itself and its reciprocal when referring to the relationship. Thus, by way of example and as will be recognized by those skilled in the art, the relationship may be used to convert a measurement item of color information into an item of true color information, the reverse relationship may be used in the reverse direction, or vice versa. Specifically, if at least one color conversion matrix is used as part of the relationship, the inverse relationship may be an inverse color conversion matrix or may include an inverse color conversion matrix. Thus, the relationship between color information derived from an image, such as measured reference color values, and corresponding known color information, such as known reference color values, may be invertible such that the relationship can convert color information derived from the image into the corresponding known color information or vice versa. For example, the relationship may be a linear conversion represented by a matrix, specifically a color conversion matrix, or may include it. The color conversion matrix may be a linear conversion from one predetermined color coordinate system, such as a measured R, G, B color coordinate system, to another color coordinate system, such as a true R, G, B color coordinate system.Therefore, as an example, the measured reference color value R. 測定された , G 測定された and B 測定された of at least some, and the corresponding known reference color values R 現実 , G 現実 and B 現実 The relationship between may be at least one color conversion matrix, or may include at least one color conversion matrix.

Number

[0030] The coefficients can determine the relationship. The coefficients CCN of the color conversion matrix ij can be determined by solving the linear equations derived from Equation (1). Coefficients, and thus relationships, in order to determine, for a plurality of color reference fields, the color coordinates R 測定された , G 測定された and B 測定された can be measured, and Equation (1) can be solved correspondingly. When multiple color coordinates of multiple color reference fields are measured, Equation (1) can be overdetermined, and statistical results such as the best fit of the coefficients, including statistical information about uncertainties or deviations such as the standard deviation or deviation of the results from the expected values, can be derived, as outlined in more detail below.

[0031] However, it should be noted that in addition to the color conversion matrix, other relationships are possible.

[0032] As outlined above, the method includes, in step iv., deriving at least one quality information item. The term "quality information item" as used herein is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to an item of information that certifies or quantifies the quality of a color reference card or a part thereof according to the above definition of "quality". Specifically, a quality information item can include numerical information specifying quality. Thus, a quality information item can include digital information describing the quality of a color reference card. Specifically, a quality information item may be or include a numerical value indicating the quality of a color reference card. A quality information item can also include information regarding the quality of at least one color reference field included in the color reference card. A quality information item can specifically be derived by using the relationship between the measured reference color value and the corresponding known reference color value determined in step iii. For example, as outlined above, a relationship such as the matrix of formula (1) can be derived by using statistical methods or fitting. A quality information item can be derived by using information regarding the quality of the fitting, such as at least one of the fitting residuals or standard deviations that quantify the quality of the fitting of the relationship. As another example, a quality information item can include the deviation of the color values of the color reference field. Specifically, the deviation may be the difference in color values obtained by comparing the expected reference color value with the known reference color value. As used herein, the term "expected reference color value" can refer to the expected reference color value of the color reference field. Specifically, the expected reference color value can refer to the predicted measured reference color value obtained by converting the known reference color value of the color reference field by using the relationship determined in step iii. Alternatively and / or additionally, the expected reference color value can also refer to the expected reference color value obtained by converting the measured color value of the color reference field by using the relationship determined in step iii.

[0033] The quality information item can further indicate the color standard field specific quality of the color standard card. Therefore, the quality information item can include a plurality of quality information or a plurality of quality information indicating the quality of each color standard field included in the color standard card. Specifically, this method can include, in step iv., deriving at least one quality information item for each color standard field of the color standard card. The quality information item can include a quantitative measure of each color standard region regarding the degree of fitness for use in a method for determining the concentration of an analyte in a body fluid. As an example, the quality information item can indicate damage to a specific color standard field. For example, the quality information item can indicate whether the color standard field is damaged, scratched, and / or faded, and thus whether the color value of the color standard field is distorted. As another example, the quality information item can indicate a color standard field that cannot be reasonably evaluated due to the influence of an interfering environment, such as interfering lighting conditions. In both examples, each color standard field may be excluded from determining the relationship in step iii. Therefore, as an example, summarizing at least one quality information item can specifically include indicating damage to a specific color standard field, specifically, indicating whether the color standard field is at least one of damaged, scratched, faded, or distorted, indicating a reason for preventing the evaluation of a specific color standard field, specifically, indicating whether the color standard field is affected by an interfering environment, and more specifically, indicating whether the color standard field is affected by interfering lighting conditions, and can include at least one of them.

[0034] As outlined above, step iii. of the present method involves determining the relationship between the measured reference color values and the corresponding known reference color values. Specifically, the determination of the relationship can include adapting the measured reference color values to the corresponding known reference color values. The adaptation can include a mathematical relationship between the measured reference color values and the corresponding known reference color values. Thus, the derivation of the quality information in step iv. can include determining at least one adaptation residual that quantifies the quality of the adaptation. As used herein, the term "adaptation residual" can refer to a statistical value indicating the deviation of at least one measured quantity from a mathematical relationship describing the measured quantity. Specifically, the adaptation residual can quantify the deviation of the measured reference color values from the relationship adapted in step iii. of the present method. For example, the adaptation residual can be, or include, at least one sum of squared residuals.

[0035] As outlined above, the measured color reference values and the known reference color values can specifically include color coordinates in a predetermined color coordinate system, specifically R, G, B color coordinates. The predetermined color coordinate system can be provided automatically or by human action. For example, the predetermined color coordinate system can be the sRGB color space, where "sRGB" represents "standard red, green, blue". As another example, the predetermined color coordinate system can be the CIE-XYZ color space. However, other options are also possible. The predetermined color coordinate system can be predetermined by using the camera of a mobile device and thus can be provided automatically by using the mobile device. As another example, the color coordinate system can be changed by human action such as the actions of the user of the mobile device.

[0036] The relationship between the measured reference color values and the known reference color values can, as outlined above, specifically include a color transformation matrix, specifically a color correction matrix, more specifically a color transformation matrix that transforms the color coordinates of the measured color reference values to the color coordinates of the known reference color values, or vice versa. The color transformation matrix can represent a linear transformation and can be invertible.

[0037] At least one quality information item derived in step iv may be derived at least in part by using the relationships determined in step iii and by converting the measured color coordinates of at least one first color reference field to the predicted color coordinates of at least one second color reference field by using the relationships. By further comparing the predicted color coordinates of the second color reference field with the measured color coordinates of the second color reference field, at least one quality information item can be derived. Specifically, the predicted color coordinates of at least one second color reference field can be obtained by converting the measured color coordinates of at least one first color reference field by using the relationships determined in step iii. The first and second color reference fields can have similar color reference values, thus making it possible to compare the predicted color coordinates of the second color reference field with the measured color coordinates of the second color reference field.

[0038] Furthermore, at least one quality information item can be determined by selectively excluding the measured reference color values of at least one selected color reference field in step iii, while the color coordinates of other color reference fields are considered in step iii. The at least one selected color reference field may specifically be excluded in step iii to determine relationships such as a color conversion matrix. At least one quality information, such as at least one conformity residual, can be derived for a particular set of this color reference field without at least one first selected color reference field. To evaluate the derived quality information item, a second set of color reference fields is used, especially without a second selected color reference field, specifically to determine a relationship different from the first selected color reference field. For each color reference field, it can be selected and excluded once in step iii to evaluate the quality of the color reference card, specifically the color reference field.

[0039] Thereby, a plurality of quality information items can be determined by selectively excluding the measured reference color values of the plurality of selected color reference fields respectively, and the quality information items can be compared specifically to identify damaged color reference fields and to identify color reference fields with low quality. Therefore, when comparing a plurality of quality information, by determining a set of color reference fields with high quality compared to other sets of color reference fields, specifically, by identifying a set of color reference fields with the minimum conformity residual, the worst attacker of the color reference fields can be identified. The worst attacker of the color reference fields can be excluded in step iii.

[0040] Therefore, generally, by determining at least one expected value and using one or more other color references to compare the expected value with the actual value of each color reference field, cross-verification of the quality of one or more color reference fields can be performed. Thereby, the quality of one or more, and even all, of the color reference fields of the color reference card can be determined, for example, iteratively. Specifically, damaged or deteriorated color reference fields can be identified.

[0041] Therefore, low-quality color reference fields can be marked and excluded in step iii. By selectively excluding low-quality color reference fields, the quality of the relationship can be enhanced. The relationship in step iii can be determined by using only those color reference fields with high quality, specifically, with low conformity residuals.

[0042] A color reference card can be configured to be used in a method for determining the concentration of an analyte in a body fluid by using a mobile device having a camera. Here, at least one image of a reagent test area of an optical test strip coated with a sample of the body fluid can be captured by the camera. The analyte concentration can be determined based on the color reaction in the reagent test area.

[0043] Accordingly, in a further aspect of the present invention, a method for determining the concentration of an analyte in a body fluid is disclosed. The method includes using a mobile device having at least one camera, and the method further includes using at least one optical test strip and at least one color reference card including a plurality of color reference fields having known reference color values.

[0044] The method may include, by way of example, the following steps that may be performed in a given order. However, it should be noted that different orders are also possible. Further, one or more method steps may be performed once or repeatedly. Further, two or more method steps may be performed simultaneously or in a timely overlapping manner. The method may include additional method steps not described.

[0045] The method further includes a. evaluating the quality of the reference card using a method according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments further disclosed in detail below; and b. capturing at least one image of at least one reagent test area of an optical test strip coated with a sample of the body fluid by using the camera; and c. determining the analyte concentration based on the color reaction in the reagent test area taking into account the result of step a.

[0046] The term "determining the concentration of an analyte in a body fluid", also referred to herein as "analytical measurement", is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to the quantitative and / or qualitative determination of at least one analyte in any sample or aliquot of a body fluid. For example, the body fluid can include one or more of blood, interstitial fluid, urine, saliva, or other types of body fluids. The result of the determination of the concentration can be, by way of example, the concentration of the analyte and / or the presence or absence of the analyte being determined. Specifically, by way of example, the determination can be a blood glucose measurement, and thus the result of the determination can be, for example, the blood glucose concentration. In particular, the analytical measurement result value can be determined by an analytical measurement.

[0047] Accordingly, the term "analyte concentration value", often also referred to herein as "analytical measurement result value", is a broad term and should be given its ordinary and customary meaning to those of ordinary skill in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to the numerical indication of the analyte concentration in a sample.

[0048] By way of example, at least one analyte can be or can include one or more specific chemical compounds and / or other parameters. By way of example, one or more analytes involved in metabolism such as blood glucose can be determined. Additionally or alternatively, other types of analytes or parameters, such as, for example, pH value, can be determined.

[0049] The method for determining the concentration of an analyte in a body fluid further includes using a mobile device having at least one camera. Further, the method includes using at least one optical test strip.

[0050] As used herein, the term "optical test strip" is a broad term and should be given its ordinary and customary meaning to one of ordinary skill in the art and should not be limited to a special or customized meaning. This term can specifically, but not exclusively, refer to any element or device configured to perform a color change detection reaction. The optical test strip can also be referred to as a test strip or test element, and all three terms can refer to the same element. The optical test strip can in particular have a test field containing at least one test chemical for detecting at least one analyte. By way of example, the optical test strip can include at least one substrate such as at least one carrier having at least one test field applied thereto or incorporated therein. In particular, the optical test strip can further include at least one white area, such as a white field, specifically in proximity to the test field, for example surrounding or enclosing the test field. The white area can be a separate field disposed independently on the substrate or carrier. However, additionally or alternatively, the substrate or carrier itself can be or can include a white area. By way of example, at least one carrier can be strip-shaped, thereby making the test element a test strip. These test strips are generally widely used and are available. One test strip can carry a single test field or multiple test fields containing the same or different test chemicals therein.

[0051] Further as used herein, the term "reagent test area", also referred to as "test field", is a broad term and should be given its ordinary and customary meaning to one of ordinary skill in the art and should not be limited to a special or customized meaning. This term can specifically, but not exclusively, refer to an aggregated amount of test chemical, such as a circular, polygonal or rectangular shaped field or area having one or more layers of a material having at least one layer of a test field containing a test chemical.

[0052] The method includes determining an analyte concentration value based on the color development in a reagent test area. Thus, the method can be an analytical measurement that includes inducing a test reaction between a test chemical and a sample of a body fluid or a part thereof, such as at least one analyte, specifically an analyte-specific test reaction, where the test reaction includes a change in color of a reagent test area that indicates the degree of the test reaction and / or the presence or concentration of the analyte. The color development can include any change in at least one optical property of an optical test strip or specifically the reagent test area, and this change can be optically measured or determined by using a camera. Specifically, the analytical measurement can be, or can include, a color development reaction in the presence of at least one analyte to be determined. As used herein, the term "color development reaction" is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. This term can specifically refer to, but is not limited to, a chemical, biological, or physical reaction in which the color, specifically the reflectance, of at least one element involved in the reaction changes as the reaction progresses. The color development can be detected by a mobile device, such as by a processor of the mobile device, and can be quantitatively evaluated, such as by deriving at least one parameter for quantifying or characterizing the color development of the reagent test area due to the presence of an analyte in a sample of body fluid from at least one image. As an example, one or more of the color coordinates described above can be used. Thus, a mobile device, specifically a processor of the mobile device, can be configured to determine a color change by determining a change in one or more color coordinates resulting from the detection reaction.

[0053] At least one analyte concentration value is determined from the color development of the reagent test area. For this purpose, at least one image can be used. The analyte concentration value can be, for example, a numerical indicator of the result of an analytical measurement, such as indicating the concentration of at least one analyte in a sample, such as a blood glucose concentration.

[0054] As an example, when capturing at least one image of the reagent test area, at least one color reference card may be within the field of view of the camera, and thus at least a portion of the color reference card may be visible within at least one image of at least a portion of the reagent test area. As an example, the optical test strip may be placed on the color reference card and / or the color reference card may comprise one or more windows, and the color reference card having one or more windows is placed on the optical test strip such that the reagent test area is visible through the window. However, alternatively, it is also possible to capture separate images of at least one reagent test area and the color reference card.

[0055] The use of the color reference card can specifically enable correction of at least one camera-specific or device-specific change in the color of the reagent test area. Thus, typically, the camera and / or mobile device applies one or more evaluation or pre-evaluation algorithms, such as gamma correction, to the image that must be taken into account when evaluating the image and determining at least one analyte concentration value without notifying the user. Specifically, at least one evaluation or pre-evaluation algorithm can be applied to the image captured in step i. Thus, subsequent steps of the method for evaluating the quality of the color reference card can specifically take into account the intensity-corrected image, and the intensity correction can include at least one evaluation or pre-evaluation algorithm such as gamma correction. Further, steps ii., iii., and iv. of the method for evaluating the quality of the color reference card can be applied to an image having acceptable linear characteristics, in particular, an evenly illuminated image, such as an image without shadows, and / or an image intensity-corrected, for example, by gamma correction. By using at least one color reference card having known optical characteristics, the mobile device can be set to calibrate and / or correct the image, and thus, when determining or before determining at least one analyte concentration value, the internal processes of the camera and / or mobile device can be taken into account. As outlined above, the method for determining the concentration of an analyte in a body fluid includes the results of the method for evaluating the quality of the color reference card. In that case, a relationship can be used to correct the measured color values of the captured image. Specifically, a high-quality relationship can be used for the analytical measurement in step c.

[0056] In a further aspect of the invention, a mobile device is disclosed, wherein the mobile device has at least one camera, the mobile device further has at least one processor, and the mobile device is configured to perform a method for evaluating the quality of a color reference card according to the invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments further disclosed in detail below.

[0057] The mobile device can be further configured to determine the concentration of an analyte in a body fluid by using at least one optical test strip, such as by performing steps b. and c. of a method for determining the concentration of an analyte in a body fluid according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below, which are related to the present invention.

[0058] As used herein, the term "processor" is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. Specifically, without limitation, this term can refer to any logic circuit configured to perform the basic operations of a computer or system and / or generally to a device configured to perform computational or logical operations. In particular, a processor can be configured to process the basic instructions that drive a mobile device, a computer, or a system. By way of example, a processor can include at least one arithmetic logic unit (ALU), at least one floating point unit (FPU) such as a numeric co-processor or a numeric coprocessor, a plurality of registers, specifically registers configured to supply operands to the ALU and store the operation results, and memory such as L1 and L2 cache memories. In particular, a processor can be a multi-core processor. Specifically, a processor can be or can include a central processing unit (CPU). Additionally or alternatively, a processor can be or can include a microprocessor, and thus, specifically, the elements of a processor can be included in one single integrated circuit (IC) chip. Additionally or alternatively, a processor can be or can include one or more application specific integrated circuits (ASICs) and / or one or more field programmable gate arrays (FPGAs), etc.

[0059] The processor may be specifically configured by, for example, software programming to execute and / or support one or more of the method steps of a method for evaluating the quality of a color reference card. Specifically, the processor may be configured to support the capture of an image of at least a portion of the color reference card by prompting the user to capture an image and / or by detecting the color reference card within the field of view and automatically capturing the image. Further, the processor may be configured to identify a color reference field on the captured image and determine its measured reference color value. The processor may be configured to assign known reference color values to corresponding measured color reference fields. Thus, the processor may be configured to determine the relationship between the measured reference color value and the corresponding known reference color value, for example, by adapting the measured reference color value to the corresponding known reference color value. The processor may be able to determine a relationship, such as a linear transformation like a color conversion matrix, using a linear optimization technique. Further, the processor may be configured to derive at least one quality information item regarding the quality of the color reference card by using the relationship.

[0060] Furthermore, the processor may be configured to execute and / or support method steps of a method for determining the concentration of an analyte in a body fluid, such as by software programming. Specifically, the processor may be configured to support the capture of at least one image of at least one reagent test area of an optical test strip to which a sample of the body fluid is applied, by using a camera of the mobile device. The processor may be further configured to determine at least one analyte concentration value from the color development of the reagent test area, such as by evaluating the image, deriving changes in one or more color coordinates resulting from a color reaction, and converting the changes in the one or more color coordinates into at least one analyte concentration value. Specifically, the processor may be configured to support one or more or all of steps b. and c. of the method for determining the concentration of an analyte in a body fluid, such as for capturing at least one image and for further providing an instruction to the user that the capture of at least one image requires the capture of at least one image of at least one color reference card. The processor may be further configured to support the application of the sample to the optical test strip, such as by providing user guidance in a visual format or an audible format. The processor may be further configured to support the capture of at least one image, such as by automatically detecting the optical test strip or a portion thereof within the field of view and / or prompting the user to capture an image.

[0061] In a further aspect of the present invention, there is provided a kit comprising at least one mobile device according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below, etc., of the present invention, and further comprising at least one color reference card, the color reference card comprising a plurality of color reference fields having known reference color values. As used herein, the term "kit" is a broad term and should be given its ordinary customary meaning to those skilled in the art and should not be limited to a special or customized meaning. This term can specifically, but not limitedly, by way of example, refer to a combination of at least two items that can be jointly supplied in a package that can interact to meet at least one common purpose.

[0062] The kit can further comprise at least one optical test strip having at least one reagent test area.

[0063] In a further aspect of the present invention, there is provided a computer program which, when executed by a mobile device according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below, etc., of the present invention, causes the processor of the mobile device to execute a method for evaluating the quality of a color reference card according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below, etc., of the present invention.

[0064] The computer program can further comprise instructions which, when the program is executed by the mobile device, cause the processor of the mobile device to execute steps b and c of a method for determining the concentration of an analyte in a body fluid.

[0065] In a further aspect of the present invention, there is disclosed a computer-readable storage medium, which, when a program is executed by a mobile device according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in more detail below, causes a processor of the mobile device to execute a method for evaluating the quality of a color reference card according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in more detail below.

[0066] The computer-readable storage medium may further include instructions that, when the program is executed by the mobile device, cause the processor of the mobile device to execute steps b and c of a method for determining the concentration of an analyte in a body fluid.

[0067] As used herein, the term "computer-readable storage medium" can specifically refer to non-transitory data storage means such as a hardware storage medium storing computer-executable instructions. The computer-readable data carrier or storage medium can specifically be or include a storage medium such as random access memory (RAM) and / or read-only memory (ROM).

[0068] The computer program may also be embodied as a computer program product. As used herein, a computer program product can refer to a program as a tradable product. The product generally exists in any format such as a paper format or on a computer-readable data carrier and / or a computer-readable storage medium. Specifically, the computer program product may be distributed on a data network.

[0069] As an example, at least one quality information item may be, or may include, a conformity residual that quantifies the quality of conformity. A high value of the conformity residual can indicate a non-linear transformation between the measured reference color value and the known reference color value. Thus, color correction of the image by using a color conversion matrix may be invalidated.

[0070] Additionally or alternatively, at least one quality information item may be, or may include, at least one quality information item derived by evaluating the quality of color correction by using one or more test fields having known reference color values. The measured color values of the test fields may be transformed using relationships such as a color conversion matrix, and thus, the transformed color values may be compared with the known reference values of the test fields. The test fields may be additional color fields included in a color reference card and / or may be selected from a plurality of color reference fields. The test fields may also be dynamically selected from a plurality of color reference fields, for example, such that the color values of the selected color reference fields can be made similar to the color values of the reagent test area. Thus, the evaluation of color correction may be according to the color development of the reagent test area. Thus, the quality and accuracy of color correction can be evaluated by using a quality information item that includes the deviation of the transformed color values of the test fields from the corresponding known reference color values.

[0071] The usefulness of one or more single-color reference fields for color correction can be evaluated using an exemplary embodiment of a method for evaluating the quality of a color reference card. As an example, when determining a relationship, specifically a color conversion matrix, one or more of the color reference fields can be selectively excluded. The relationship, specifically the color conversion matrix, may be determined using the remaining color reference fields, specifically without the selected color reference fields. The excluded color reference field may be used as a test field. The color conversion matrix may be determined by selecting each of the color reference fields as a test field at least once.

[0072] For each set of color reference fields and test fields, at least one quality information item such as the deviation of the converted color value of the test field from the known color reference value of the test field of the conformity residual can be derived. The quality information item can enable an evaluation of the quality of color correction for each color reference field. If a damaged color reference field can be excluded in the determination of the color conversion matrix, the corresponding conformity residual will be low compared to the set of other conformity residuals, and the deviation of the expected reference color value from the known color value will increase for the corresponding color reference field. A color reference field with a low value of the quality information item, such as less than a threshold value, may be excluded for the determination of the color conversion matrix. Alternatively and / or additionally, the analyte measurement may be cancelled due to a defective color reference card and / or poor image quality.

[0073] The method for evaluating the quality of the color reference card may be included in the method for determining the concentration of an analyte in a body fluid using a camera of a mobile device. The method can further include using at least one optical test strip, and the optical test strip, specifically the reagent test area, can undergo a color reaction when a sample of body fluid is applied thereto. The color subspace of the corresponding color reaction can be determined using a spectrometer. The color value of the color reference field may be selected from the color subspace of the color reaction.

[0074] The relationship between the measured reference color value and the known reference color value may be determined by using at least one color conversion matrix as outlined above. A conformity residual that quantifies the quality of conformity is used to evaluate the quality of the color conversion matrix.

[0075] Table 1 shows an exemplary embodiment of a method for evaluating the quality of a color reference card. Since each color reference field is selected as a test field, it is excluded from determining the color conversion matrix. The corresponding fitting residuals and the deviations of the converted measured color values of the test fields from their known reference color values are calculated. In this example, the color reference card has no visible damage, and thus the color reference card can have high quality with low fitting residuals and low deviations. [Table 1] Table 1: An exemplary embodiment for evaluating the quality of a color reference card or a part thereof, wherein the color reference card comprises a plurality of color reference fields, and in this example, has high quality.

[0076] Furthermore, Table 2 shows an example of a color reference card including at least partially damaged color reference fields. In this example, color reference fields numbered 5 and 6 may be damaged. The results of the method for evaluating the quality of the color reference card are shown in the upper two rows of Table 2. The deviations of the converted measured color values of the damaged color reference fields from their known reference color values are high compared to each of the other color reference fields. Further, when the damaged color reference fields are excluded from the determination of the color conversion matrix, the fitting residuals can be reduced. Defective color reference fields can be determined by identifying color reference fields with low quality, e.g., lower fitting residuals and higher deviations. One of the worst attackers can be excluded from the fitting, and the fitting residuals and deviations can be improved. It may also be possible to exclude one or more defective color reference fields to improve the quality of the fitting of the color conversion matrix. [Table 2] Table 2: An exemplary embodiment for evaluating the quality of a color reference card or a part thereof, wherein the color reference card comprises a plurality of color reference fields, and in this example, has low quality due to damaged color reference fields etc.

[0077] The method and apparatus according to the present invention provide many advantages over similar methods and apparatuses known in the art. The method and apparatus described herein can provide an easy-to-use and reliable method for determining the concentration of at least one analyte in a body fluid while ensuring high accuracy of the analytical measurement. Specifically, the color reference card can be used to correct the measured color value by taking into account the relationship, specifically the color conversion matrix. Therefore, color correction, specifically color correction of the captured image of the reagent test area, can improve the accuracy of the analytical measurement.

[0078] Furthermore, by using a method for evaluating the quality of the color reference card, the quality of the color reference card can be checked. Specifically, the color reference card may be checked before or when used for analytical measurement. The present method and apparatus can ensure the high reliability of the color reference card and thus the high accuracy of the analytical measurement.

[0079] Furthermore, a color reference card having defects can be identified. The color reference card may be sorted, and / or only a limited number of color reference fields may be used for actual analytical measurement. Specifically, one or more non-intact color reference fields, such as damaged color reference fields, can be excluded from the analytical measurement. Therefore, the present method and apparatus enhance safety compared to known methods and apparatuses.

[0080] Furthermore, the method and apparatus according to the present invention enable the use of a greater variety of models of mobile devices for analytical measurement. By using a quality-checked color reference card, the analytical measurement can provide a means for accurate analytical measurement of the analyte concentration in a body fluid even with a wide variety of different mobile devices.

[0081] In summary, the following embodiments can be envisioned without excluding the possibility of further embodiments:

[0082] Embodiment 1: A method for evaluating the quality of a color reference card, the color reference card comprising a plurality of color reference fields having known reference color values, the method comprising: i. capturing at least one image of at least a part of the color reference card by using at least one camera of at least one mobile device; ii. determining measured reference color values for at least some of the color reference fields from the image; iii. determining a relationship between at least some of the measured reference color values and the corresponding known reference color values; iv. deriving at least one quality information item regarding the quality of the color reference card by using the relationship of step iii.

[0083] Embodiment 2: The method according to the preceding embodiment, wherein determining the relationship in step iii. comprises adapting the measured reference color values to the corresponding known reference color values.

[0084] Embodiment 3: The method according to the preceding embodiment, wherein deriving the quality information in step iv. comprises determining at least one adaptation residual that quantifies the quality of the adaptation.

[0085] Embodiment 4: The method according to any one of the preceding embodiments, wherein the measured reference color values and the known reference color values each comprise color coordinates in a predetermined color coordinate system, specifically R, G, B color coordinates.

[0086] Embodiment 5: The method according to any one of the preceding embodiments, wherein the relationship between the measured reference color values and the known reference color values comprises a color transformation matrix, specifically a color correction matrix, more specifically a color transformation matrix that transforms the color coordinates of the measured reference color values to the color coordinates of the known reference color values, or vice versa.

[0087] Embodiment 6: The method according to any one of the preceding embodiments, wherein at least one quality information item in step iv is at least partially derived by using the relationship determined in step iii and using the relationship to further compare the expected color coordinates of the second color reference field with the measured color coordinates of the second color reference field, and converting the measured color coordinates of at least one first color reference field into the expected color coordinates of at least one second color reference field.

[0088] Embodiment 7: The method according to any one of the preceding embodiments, wherein at least one quality information item is determined by selectively excluding the measured reference color values of at least one selected color reference field in step iii, while the color coordinates of other color reference fields are considered in step iii.

[0089] Embodiment 8: The method according to the preceding embodiments, wherein a plurality of quality information items are determined by selectively excluding the measured reference color values of a plurality of selected color reference fields respectively, and the quality information items are compared specifically to identify damaged color reference fields and to identify color reference fields with low quality.

[0090] Embodiment 9: The method according to any one of the preceding embodiments, wherein the color reference card is configured to be used in a method for determining the concentration of an analyte in a body fluid by using a mobile device having a camera, at least one image of a reagent test area of an optical test strip coated with a sample of the body fluid is captured by the camera, and the analyte concentration is determined based on a color reaction in the reagent test area.

[0091] Embodiment 10: A method for determining the concentration of an analyte in a body fluid, the method comprising using a mobile device having at least one camera, the method further comprising using at least one optical test strip and at least one color reference card including a plurality of color reference fields having known reference color values, the method a. evaluating the quality of the reference card using the method according to any one of Embodiments 1 to 9; b. capturing at least one image of at least one reagent test region of the optical test strip on which a sample of the body fluid is applied by using the camera; c. determining the analyte concentration based on the color reaction of the reagent test region, taking into account the result of step a.

[0092] Embodiment 11: A mobile device having at least one camera, the mobile device further having at least one processor, the mobile device being configured to execute a method for evaluating the quality of the color reference card according to Embodiment 10.

[0093] Embodiment 12: The mobile device according to the preceding embodiment, further configured to determine the concentration of an analyte in a body fluid by using at least one optical test strip by executing steps b. and c. of the method according to Embodiment 10.

[0094] Embodiment 13: A kit comprising at least one mobile device according to any one of the two preceding embodiments, further comprising at least one color reference card, the color reference card comprising a plurality of color reference fields having known reference color values.

[0095] Embodiment 14: The kit according to the preceding embodiment, further comprising at least one optical test strip having at least one reagent test region.

[0096] Embodiment 15: When a program is executed by the mobile device according to Embodiment 11 or 12, a computer program including an instruction to cause a processor of the mobile device to execute a method for evaluating the quality of the color reference card according to any one of Embodiments 1 to 9.

[0097] Embodiment 16: When a program is executed by the mobile device, a computer program according to the preceding embodiment, further including an instruction to cause a processor of the mobile device to execute steps b. and c. of the method according to Embodiment 10.

[0098] Embodiment 17: When a program is executed by the mobile device according to Embodiment 11 or 12, a computer-readable storage medium including an instruction to cause a processor of the mobile device to execute a method for evaluating the quality of the color reference card according to any one of Embodiments 1 to 9.

[0099] Embodiment 18: When a program is executed by the mobile device, a computer-readable storage medium according to the preceding embodiment, further including an instruction to cause a processor of the mobile device to execute steps b. and c. of the method according to Embodiment 10.

[0100] Any further optional features and embodiments are preferably disclosed in more detail in the subsequent description of the embodiments in conjunction with the dependent claims. Here, each optional feature may be implemented in an independent manner and in any feasible combination, as will be understood by those skilled in the art. The scope of the present invention is not limited by the preferred embodiments. The embodiments are schematically shown in the figures. Here, the same reference signs in these figures refer to the same or functionally equivalent elements.

Brief Description of the Drawings

[0101] The figures are as follows:

Fig. 1a-1b

Fig. 2

Fig. 3

Fig. 4

DETAILED DESCRIPTION OF THE INVENTION

[0102] DETAILED DESCRIPTION OF THE EMBODIMENTS In FIGS. 1a-1b, an exemplary embodiment of a color reference card 110 is shown in a perspective view. The color reference card 110 includes a plurality of color reference fields 112 having known reference color values. The color reference fields 112 may be in a pristine state as seen in FIG. 1a. The color reference fields 112 may also be at least partially defective, for example, by damage, scratching, etc., as symbolically indicated by the defective color reference field 113 in FIG. 1b.

[0103] The color reference field 112 may be disposed on the surface of the color reference card 110, such as on the base material of the color reference card 110. In particular, the color reference fields 112 can be evenly distributed across the entire surface of the color reference card 110, especially such that a plurality of color reference fields 112 can be distributed across the entire surface of the color reference card 110. By way of example, the color reference fields 112 may be arranged in a matrix pattern, such as a rectangular matrix pattern. However, the color reference fields 112 may also be arranged in other ways, such as being separate from each other. For example, the color reference card 110 can include a plurality of gray color reference fields 114 that surround the color reference fields 112. The color reference fields 112 and the gray color reference fields 114 may not overlap each other. In an exemplary embodiment of the color reference card 110, the color reference fields 112 and the gray color reference fields 114 may be printed on a pre-printed gray background of the color reference card 110. Accordingly, the color reference fields 112 may overlap the gray background of the color reference card 110.

[0104] The color reference card 110 can further include at least one window 116. Accordingly, at least one optical test strip 118 or a portion thereof can be viewed through the window 116 when the color reference card 110 is placed on top of the optical test strip 118. Specifically, at least one reagent test area 120 included in the optical test strip 118 can be viewed through the window 116 of the color reference card 110. As another example, the color reference card 110 may include an optical test strip 118 having at least one reagent test area 120, specifically such that at least one reagent test area 120 is accessible and visible.

[0105] Furthermore, the color reference card 110 may include at least one marker 122. The marker 122 may be, for example, at least one of position markers such as an ArUco code, a barcode, a QR code (registered trademark), a label, or a combination thereof, or may include it. In FIGS. 1a and 1b, the marker 122 may specifically include one or more ArUco codes at corners of a rectangular matrix including the color reference field 112. Thus, generally, the marker 122 can be arranged at at least one corner 124 of the color reference card 110. For example, at least one marker 122 may be arranged at each of the corners 124 of the color reference card 110, especially so that the marker 122 can be seen together with a plurality of color reference fields 112. Furthermore, the marker 122 can include information regarding the orientation of the color reference card 110.

[0106] In FIGS. 1a and 1b, the color reference fields 112 can include fields having different colors, for example, a color reference field 112 having black (indicated by reference numeral 148), a color reference field 112 having one or more gray colors (indicated by reference numeral 150), a color reference field 112 having white (indicated by reference numeral 152), and / or a color reference field 112 having one or more colors such as blue, green, red, and / or a mixed color thereof (indicated by reference numeral 154). The gray color reference field 114 can include a field having one or more gray colors (indicated by reference numeral 150), similar to the color reference field 112.

[0107] FIG. 2 shows an exemplary embodiment of a kit 126 for performing analytical measurements in a perspective view. The kit 126 includes at least one mobile device 128 and at least one color reference card 110. Furthermore, the kit 126 can include at least one optical test strip 118.

[0108] The mobile device 128 may be or may include at least one of a mobile phone, a smartphone, a tablet computer, etc. Further, the mobile device 128 has at least one camera 130. The camera 130 of the mobile device 128 may be configured to record an image, specifically a color image. Thus, the camera 130 may be a color camera and may include at least three color sensors, such as at least one color sensor for R, G, and B colors.

[0109] Furthermore, the mobile device 128 can include at least one processor 132. The processor 132 may be configured to perform one or more of the method steps of a method for evaluating the quality of the color reference card 110, specifically by software programming. Further, the processor 132 may be configured to support one or more of steps b and c of a method for determining the concentration of an analyte in a body fluid. Exemplary embodiments of the methods described above are shown in FIGS. 3 and 4, respectively, and are described in more detail below. Thus, reference can be made to the descriptions of FIGS. 3 and 4.

[0110] Specifically, the processor 132 may be configured to support the capture of at least one image of the color reference card 110. Specifically, the processor 132 can prompt the user of the mobile device 128 to capture an image. Additionally or alternatively, the processor 132 may be configured to automatically capture an image of the color reference card 110, specifically when the color reference card 110 is within the field of view.

[0111] The color reference card 110 can be embodied, specifically, according to any one of the embodiments disclosed in FIGS. 1a - 1b, as described in more detail above. The color reference card 110 includes a plurality of color reference fields 112 having known reference color values. Further, the color reference card 110 can include at least one window 116. Thus, the optical test strip 118 can be viewed through the window 116 of the color reference card 110, specifically, when the color reference card 110 can be placed on top of the optical test strip 118 such that both the color reference card 110 and the optical test strip 118 can be viewed on at least one image captured by the camera 130 of the mobile device 128. Specifically, at least one reagent test area 120 of the optical test strip 118 can be viewed through the window 116 of the color reference card 110.

[0112] The color reference card 110 can further include at least one marker 122. The marker 122 can be disposed on at least one surface of the color reference card 110 such that the marker 122 can be detectable by the camera 130 of the mobile device 128. The at least one marker 122 may be used to identify the orientation of the color reference card 110. Specifically, the processor 132 of the mobile device 128 can be configured to detect the marker 122 on the image captured by the camera 130 and further obtain information regarding the orientation of the color reference card 110.

[0113] FIG. 3 shows a flowchart of an exemplary embodiment of a method for evaluating the quality of the color reference card 110 (reference numeral 134 in FIGS. 3 and 4). The method includes the following steps that can be executed, specifically, in a given order. Further, different orders are also possible. Two or more method steps can be executed completely or partially simultaneously. Further, one, two or more, or all of the method steps can be executed once or repeatedly. The method can include additional method steps not described.

[0114] This method includes: i. Capturing at least one image of at least a part of the color reference card 110 by using at least one camera 130 of at least one mobile device 128 (indicated by reference numeral 136); ii. Determining reference color values measured for at least some of the color reference fields 112 from the image (indicated by reference numeral 138); iii. Determining the relationship between at least some of the measured reference color values and the corresponding known reference color values (indicated by reference numeral 140); iv. Deriving at least one quality information item regarding the quality of the color reference card 110 by using the relationship of step iii. (indicated by reference numeral 142).

[0115] In step i, the capturing of at least one image of at least a part of the color reference card 110 may be initiated by the processor 132 of the mobile device 128. For example, the processor 132 may be configured to prompt the user to capture an image of the color reference card 110. As another example, the processor 132 may be configured to detect the color reference card 110 within the field of view by using the camera 130 of the mobile device 128 and further automatically capture the image.

[0116] Marker 122 that can be included in the color reference card 110 can be seen on the image captured in step i. Thus, the processor 132 may be configured to obtain information regarding the orientation of the color reference card 110. Further, computer vision processes and / or image analysis can be used to identify the color reference fields 112 included in the color reference card 110 and determine the reference color values measured for at least some of the color reference fields 112. For example, the measured reference color values can include color coordinates in a given color coordinate system, specifically R, G, B color coordinates. By identifying the color reference fields 112 on the color reference card 110, known reference color values can be assigned to the measured color reference fields 112. Thus, the mobile device 128 can comprise a data storage device that can be specifically configured to store the known reference color values of a plurality of color reference fields 112. The known reference color values may also include color coordinates in a given color coordinate system, such as R, G, B color coordinates.

[0117] Further, in step iii., the relationship between the measured reference color value and the corresponding known reference color value is determined. Thus, step iii. may include adapting the measured reference color value to the corresponding known reference color value. For example, the relationship may be a linear transformation represented by a matrix, such as a color transformation matrix, or may include it. The color transformation matrix may be used to correct the measured color values by converting the measured color values to true color values. Specifically, the color transformation matrix can be determined in step iii. by adapting the measured reference color values to the corresponding known color reference values. The color transformation matrix determined in step iii. can be used in a method for determining the concentration of an analyte in a body fluid, as will be described in more detail below.

[0118] In step iv., at least one quality information item regarding the quality of the color reference card 110 is derived by using the relationship in step iii., specifically, by using a color conversion matrix. As an example, step iv. can include determining at least one conformity residual that quantifies the quality of conformity. Specifically, the conformity residual can quantify the deviation of conformity with respect to the measured reference color value. For example, the conformity residual may be the sum of squared residuals or may include the sum of squared residuals.

[0119] As another example, at least one quality information item may be derived at least in part by using the relationship in step iii. and by converting the measured color coordinates of at least one first color reference field 112 to the predicted color coordinates of at least one second color reference field 112 by using the relationship, specifically, a color conversion matrix. Thus, the quality information item may be derived at least in part by comparing the predicted color coordinates of the second color reference field 112 with the measured color coordinates of the second color reference field 112.

[0120] As a further example, at least one quality information item may be derived by selectively excluding the measured color values of at least one selected color reference field 112 in step iii. The color coordinates of the other color reference fields 112 may be considered in step iii. Thus, by excluding one selected color reference field 112, a conformity residual can be derived for the set of color reference fields 112. This may be repeated at least once, twice, or even more than twice such that each of the color reference fields 112 is selected to be excluded once. Thereby, a plurality of quality information can be determined by selectively excluding the measured reference color values of a plurality of selected color reference fields 112. Thus, the quality information items may be compared to identify color reference fields 112 having low quality, specifically to identify damaged color reference fields 112. The damaged color reference fields 112 and / or color reference fields 112 having low quality may be excluded from determining the relationship in step iii.

[0121] The method for evaluating the quality of the color reference card 110 may be at least partially computer-implemented. Specifically, the mobile device 128 may be configured to execute a computer program including instructions that cause the processor 132 of the mobile device 128 to execute a method for evaluating the quality of the color reference card 110 when the program is executed by the mobile device 128.

[0122] FIG. 4 shows a flowchart of an exemplary embodiment of a method for determining an analyte concentration in a body fluid. The method includes using at least one mobile device 128 having at least one camera 130. The method further includes using at least one optical test strip 118 and at least one color reference card 110 comprising a plurality of color reference fields 112 having known reference color values.

[0123] The method specifically includes the following steps that can be executed in a given order. Furthermore, different orders are also possible. Two or more method steps can be executed completely or partially simultaneously. Furthermore, one, two or more, or all method steps can be executed once or repeatedly. The present method can include additional method steps not described.

[0124] The present method a. Evaluating the quality of the reference card 110 using a method for evaluating the quality of the color reference card 110 (indicated by reference numeral 134); b. Capturing at least one image of at least one reagent test area 120 of the optical test strip 118 having a sample of body fluid applied thereto by using a camera 130 (indicated by reference numeral 144); c. Determining the analyte concentration based on the color reaction of the reagent test area 120, taking into account the result of step a. (indicated by reference numeral 146).

[0125] In particular, evaluating the quality of the color reference card 110 in step a. of the present method can include the method according to the exemplary embodiment described in FIG. 3 above. Thus, the following steps of the analytical measurement, specifically steps b. and c., may be executed when the quality of the color reference card 110 is evaluated to be of high quality. Specifically, the analytical measurement can be executed when the quality information item indicates that the color reference card 110 is of high quality and thus the relationship determined in step iii. can be a very accurate relationship.

[0126] Therefore, the processor 132 of the mobile device 128 can receive and / or process the quality information items derived in step iv. of the method for evaluating the quality of the color reference card 110. If the quality information items indicate high quality of the color reference card 110, the processor 132 can further initiate analytical measurements, particularly steps b. and c. For example, the processor 132 can initiate further method steps by prompting the user to apply a sample of body fluid onto the reagent test area 120 of the optical test strip 118.

[0127] In step b., the capture of an image of the reagent test area 120 may be performed by the processor 132, for example, by prompting the user to capture the image and / or by automatically capturing the image.

[0128] Furthermore, the analytical measurements can include detecting the color values of the reagent test area 120 onto which a sample of body fluid has been applied and determining the analyte concentration based on the color reaction of the reagent test area 120 taking into account the results of step a. Specifically, the relationship determined in step iii. may be used to correct the measured color values of the color reaction, for example, by using a color conversion matrix. The analyte concentration can be determined by using the corrected color values.

[0129] A method for determining the concentration of an analyte in a body fluid, specifically steps b and c of this method, may be at least partially computer-implemented. The mobile device 128 can be specifically configured to execute a computer program that causes the processor 132 of the mobile device 128 to execute steps b and c of this method when executed by the mobile device 128. The processor 132 can be specifically configured to capture at least one image of the reagent test area 120, for example, by prompting the user to capture at least one image and / or by automatically capturing at least one image. For example, the image captured in step b of the method for determining the analyte concentration in a body fluid may be the same as the image captured in step i of the method for evaluating the quality of the color reference card 110. Therefore, at least one captured image can include at least a part of the color reference card 110 and at least one reagent test area 120 of the optical test strip 118.

[0130] Furthermore, the processor 132 may be specifically configured, by software programming, to determine the analyte concentration based on the color reaction in the reagent test area 120. The processor 132 may be configured to evaluate the captured image, derive the change in one or more color coordinates that occurs during the color reaction, and determine the analyte concentration by converting the change in at least one color coordinate into an analyte concentration value. Specifically, the processor 132 may be configured to use the relationship determined in step iii of the method for evaluating the quality of the color reference card 110 to derive the true color value from the captured image. Therefore, the processor 132 can correct the measured color value of the captured image by using the color conversion matrix determined in step iii of the method for evaluating the quality of the color reference card 110 to convert the measured color value into the true color value.

Description of the reference numerals

[0131] 110 Color reference card 112 Color reference field 113 Defective color reference field 114 Gray color reference field 116 Window 118 Optical test strip 120 Reagent test area 122 Marker 124 Corner 126 Kit 128 Mobile device 130 Camera 132 Processor 134 Evaluation of the quality of the color reference card 136 Capture of at least one image of at least a part of the color reference card 138 Determination of the measured reference color values 140 Determination of relationships 142 Derivation of at least one quality information 144 Capture of at least one image of at least one reagent test area 146 Determination of the analyte concentration 148 Black field 150 Gray field 152 White field 154 Color field

Claims

1. A method for evaluating the quality of a color reference card (110), wherein the quality of the color reference card (110) indicates whether the color reference card (110) can be used in a method for determining the concentration of an analyte in a body fluid, and / or refers to the fitness or reliability of the color reference card (110) for use in a method for determining the concentration of an analyte in the body fluid. The color reference card (110) includes a plurality of color reference fields (112) having known reference color values, and the method includes: i. Capturing at least one image of at least a part of the color reference card (110) by using at least one camera (130) of at least one mobile device (128); ii. Determining the reference color values measured for one or more of the color reference fields (112) from the image; iii. Determining the relationship between one or more of the measured reference color values and the corresponding known reference color values; iv. Deriving at least one quality information item regarding the quality of the color reference card (110) by using the relationship in step iii. A method comprising the above steps.

2. The step of determining the relationship in step iii. includes adapting the measured reference color values to the corresponding known reference color values, and the step of deriving the quality information item in step iv. includes determining at least one adaptation residual that quantifies the quality of the adaptation. The method according to claim 1.

3. The relationship between the measured reference color values and the known reference color values includes a color transformation matrix. The method according to claim 1 or 2.

4. The at least one quality information item in step iv. is at least partially derived by using the relationship determined in step iii., and by using the relationship and further comparing the predicted color coordinates of a second color reference field (112) with the measured color coordinates of the second color reference field (112), to transform the measured color coordinates of at least one first color reference field (112) into the predicted color coordinates of at least one second color reference field (112). The method according to any one of claims 1 to 3.

5. The method according to any one of claims 1 to 4, wherein the at least one quality information item is determined by selectively excluding the measured reference color values of at least one selected color reference field (112) in step iii., and in step iii., the color coordinates of other color reference fields (112) are taken into account.

6. The method according to claim 5, wherein a plurality of quality information items are determined by selectively excluding the measured reference color values of a plurality of selected color reference fields (112) respectively, and the quality information items are compared to identify color reference fields (112) having low quality.

7. A method for determining the concentration of an analyte in a body fluid, the method comprising using a mobile device (128) having at least one camera (130), the method further comprising using at least one optical test strip (118) and at least one color reference card (110) including a plurality of color reference fields (112) having known reference color values, the method comprising: a. evaluating the quality of the reference card (110) using the method according to any one of claims 1 to 6; b. capturing at least one image of at least one reagent test area (120) of the optical test strip (118) on which a sample of the body fluid is applied, by using the camera (130); c. determining the concentration of the analyte based on the color reaction of the reagent test area (120), taking into account the result of step a. comprising the method.

8. A mobile device (^128) having at least one camera (130), wherein the mobile device (128) further comprises at least one processor (132), the camera (130) of the mobile device (128) captures an image of at least a part of a color reference card, and the mobile device (128) is configured to execute a method for evaluating the quality of a color reference card (110) according to any one of claims 1 to 6.

9. The mobile device (128) is further configured to determine the concentration of an analyte in a body fluid by using at least one optical test strip (118) by performing steps b. and c. of the method according to claim 7, the mobile device (128) according to claim 8.

10. A kit (126) comprising at least one mobile device (128) according to claim 8 or 9 referring to the mobile device (128), further comprising at least one color reference card (110), the color reference card (110) comprising a plurality of color reference fields (112) having known reference color values.

11. The kit (126) according to claim 10, further comprising at least one optical test strip (118) having at least one reagent test area (120).

12. A computer program comprising instructions that, when the program is executed by a mobile device (128) according to claim 8 or 9 referring to the mobile device (128), cause a processor (132) of the mobile device (128) to execute a method for evaluating the quality of a color reference card (110) according to any one of claims 1 to 6.

13. The computer program according to claim 12, further comprising instructions that, when the program is executed by the mobile device (128), cause the processor (132) of the mobile device (128) to perform steps b. and c. of the method according to claim 7.

14. A computer-readable storage medium comprising instructions that, when the program is executed by a mobile device (128) according to claim 8 or 9 referring to the mobile device (128), cause a processor (132) of the mobile device (128) to execute a method for evaluating the quality of a color reference card (110) referring to a method for evaluating the quality of a color reference card (110) according to any one of claims 1 to 6.

15. The computer-readable storage medium according to claim 14, further comprising instructions that, when the program is executed by the mobile device (128), cause the processor (132) of the mobile device (128) to perform steps b. and c. of the method according to claim 7.

Images