Photometric interference determination

Abstract

The present disclosure describes a method for determining interference levels using a photometric in vitro diagnostic assay and an in vitro diagnostic analyzer for performing the method. The method includes treating an aliquot of a sample with at least one reagent to obtain a sample / reagent mixture, and performing a photometric measurement of the sample / reagent mixture to obtain the result of the in vitro diagnostic assay, and determining a preliminary interference level by semi-quantitatively determining one or more interfering substances in the same sample / reaction mixture during the same photometric measurement. The method further includes triggering an independent photometric measurement of another aliquot of the same sample, undiluted or diluted with a liquid other than a reagent, only when a preliminary interference level above a predetermined threshold is determined, so as to determine an effective interference level by quantitatively determining the one or more interfering substances.

Description

Technical Field

[0001] The present disclosure relates to a method of determining interference levels using a photometric in vitro diagnostic assay and an in vitro diagnostic analyzer for performing the method. Background Art

[0002] In medicine, physicians' diagnoses and patient treatments often rely on the measurement of analyte concentrations or other parameters in patient samples. This measurement is typically accomplished using an in vitro diagnostic analyzer that can be configured to perform in vitro diagnostic assays using a variety of detection techniques, many of which are photometrically based, including, for example, turbidimetry, scatter photometry, and colorimetry. Because the life of a patient may depend on the accuracy and reliability of such measurements, it may be important to identify and take into account any interferences that may be present in the sample and potential biases in the results of the in vitro diagnostic assay. In particular, samples may contain substances that interfere with photometric measurements. Examples of such interfering substances are hemoglobin in hemolyzed samples, bilirubin in icteric samples, elevated levels of triglycerides or other lipids and milky substances in lipid samples, contaminants such as those used in patient treatment, and other substances. etc., including combinations thereof. Therefore, it is recommended to perform a quality check simultaneously or before subjecting the sample to an in vitro diagnostic assay. In particular, the concentration of these interfering substances can be determined by measuring light absorption at different wavelengths, as known in the art.

[0003] However, this sample quality check is not always possible or desirable because, on the one hand, it uses functional resources of the analyzer such as pipettes, detectors, consumables and, in particular, by doing so, reduces the analyzer throughput, sometimes by up to 50%, if every sample is checked for the presence of interfering substances, while on the other hand, it increases the costs of the in vitro diagnostic assay and delays the time to result, which may have serious consequences, especially for urgent samples.

[0004] Therefore, some in vitro analyzers are configured such as to offer the user the option to manually enable or disable sample quality checks before all in vitro diagnostic assays or only before some in vitro diagnostic assays, accepting the risk that assay results may be biased in the event of a disturbance. Summary of the invention

[0005] In view of the above background, this article introduces a method for determining interference levels using a photometric in vitro diagnostic assay and an in vitro diagnostic analyzer for performing the method, which can minimize the use of analytical resources and the loss of throughput to minimize costs, minimize the time to results without compromising the quality of the results, and also avoid users from making risky decisions.

[0006] The method comprises treating an aliquot of the sample with at least one reagent to obtain a sample / reagent mixture, and performing a photometric measurement of the sample / reagent mixture to obtain the result of the in vitro diagnostic assay, and determining a preliminary interference level by semi-quantitatively determining one or more interfering substances in the same sample / reaction mixture during the same photometric measurement. The method further comprises, only when a preliminary interference level above a predetermined threshold is determined, triggering an independent photometric measurement of another aliquot of the same sample, undiluted or diluted with a liquid other than the reagent, in order to determine the effective interference level by quantitatively determining the one or more interfering substances.

[0007] As used herein, the term "sample" refers to a biological material suitable for performing a photometric in vitro diagnostic assay, for example, to detect one or more target analytes suspected of being present therein or to measure parameters of the sample such as color, turbidity, clotting time, etc., which parameters may also be directly or indirectly related to the presence and / or amount of the target analyte.

[0008] The sample can be from any biological source, such as physiological fluids, including blood, urine, saliva, lens fluid, cerebrospinal fluid, sweat, milk, ascites, mucus, synovial fluid, peritoneal fluid, amniotic fluid, tissue, cells, etc. The sample can be pre-treated before use, for example, preparing plasma or serum from blood. The treatment method may include filtering, centrifuging, distilling, diluting, concentrating, cracking, purifying, inactivating interfering components and adding reagents, etc. The sample can be used directly after being obtained from the source, or it can be pre-treated to change the characteristics of the sample, for example, after diluting with another solution or after mixing with a reagent, for example, to complete one or more in vitro diagnostic tests. According to one embodiment, the sample is a blood sample treated with citrate or EDTA. According to another embodiment, the sample is a serum derived from blood.

[0009] The term "reagent" is generally used to represent a required liquid or substance that can be mixed with a sample and / or other reagents, such as to react and support photometric measurements. A reagent is typically a solution containing at least one reactant, which is a chemical or biological agent that promotes the reaction when contacting with a sample, particularly an analyte in the sample. A reagent can be a compound or an agent that can, for example, bind to one or more analytes present in the sample or chemically transform the analyte, and / or can induce photometric measurable changes in the presence of an analyte in the sample. Examples of reactants include enzymes, enzyme substrates, conjugated dyes, protein binding molecules, nucleic acid binding molecules, antibodies, chelating agents, co-catalysts, inhibitors, epitopes, antigens, etc.

[0010] The term "photometric in vitro diagnostic assay" may encompass turbidity and scattered light immunoassays, turbidity clot assays, and colorimetric assays. In turbidity and scattered light immunoassays and turbidity clot assays, the specific analyte is quantified from the turbidity change of the sample / reaction mixture based on the agglutination of the specific analyte and the analyte-specific binding partner, while in colorimetric assays, the specific analyte is quantified with the aid of a chromogenic reagent. The term "chromogenic reagent" encompasses any assay reagent or mixture of assay reagents that, in the presence of the target analyte, results in a color change, color formation, or color disappearance that can be photometrically measured and quantified in a typical wavelength range of 340 nm to 800 nm. Many colorimetric assays include an enzyme and a corresponding substrate that results in a colored product in one or more step reactions; the color change can be induced by the corresponding enzyme cofactor, such as NAD / NADH, rather than the substrate itself. There are also colorimetric assays that are based on the specific reaction of an analyte with a chemical reagent that results in a colored product in one or more step reactions. In colorimetric immunoassays such as EMIT (enzyme multiple immunoassay technology) or CEDIA (cloned enzyme donor immunoassay), color is usually formed by the reaction of a reporter enzyme such as β-galactosidase or dehydrogenase with its corresponding substrate, which results in a product with characteristic and detectable absorption properties. The reaction of the reporter enzyme with the substrate usually occurs after an immunoreaction of the analyte with an antibody, which then triggers or inhibits the enzymatic reaction. In other colorimetric assays, such as in typical clinical chemistry assays, color is formed, changed or disappeared by the reaction of the analyte with an enzyme or any other specific chemical reagent or a combination thereof.

[0011] The terms "turbidimetry and scattering photometry" are methods known in the art for determining the amount of turbidity or turbidity in a solution based on measuring the effect of the turbidity on light transmission and scattering. Turbidity in a liquid is caused by the presence of tiny suspended particles. If a light beam passes through a turbid sample, its intensity is reduced due to scattering, and the amount of scattered light depends on the concentration, size, and size distribution of the particles. For example, the increased turbidity caused by an increase in particle size due to agglutination or coagulation reaction can be measured. In clinical chemistry assays, this increased turbidity can be a direct measure of the immunoagglutination caused by the analyte or a direct measure of the inhibition of immunoagglutination caused by the analyte. In coagulation assays or turbidity clot assays, this increased turbidity is a direct measure of progressive clot formation. In scattering photometry, the intensity of the scattered light is measured, while in turbidity, the intensity of the light transmitted through the sample is measured.

[0012] Turbidimetry involves measuring the intensity of an incident light beam as it passes through a sample. The light beam may pass through the suspension or be absorbed, reflected or scattered by the particles. Thus, as the light is transmitted through the suspension, its intensity decreases. For non-absorbing particles, the decrease in light intensity due to scattering is expressed as turbidity.

[0013] Scatter photometry refers to the measurement of light scattered from an incident beam at an angle θ as it passes through a sample. In scatter photometry, the intensity of the scattered light is measured as a function of time, as scattering species rapidly increase in size. The scattered light is directly proportional to the initial analyte / antigen concentration.

[0014] Particle enhanced immunoassay is routinely used in in vitro diagnosis for quantitative analysis of serum proteins, therapeutic drugs and drugs of abuse on clinical chemistry analyzers. In order to enhance the optical detection between the analyte and the analyte-specific binding partner in the reaction mixture, the analyte or the analyte-specific binding partner is connected to suitable particles. Therefore, the analyte reacts and agglutinates with the particles coated with the analyte-specific binding partner. Along with the increase of the amount of the analyte, the size of the agglutination and the complex increases, further leading to the change of light scattering. Then, the agglutinated particles are determined by turbidity and scattered light measurement.

[0015] Most particle-based assays use latex nanoparticles, which typically have an average diameter between 30 nm and 600 nm, the main type being polystyrene. A wide variety of other particle materials can also be used, including organic, inorganic, and polymeric materials.

[0016] In vitro diagnostic assays for coagulation support the measurement of the activity of individual or a number of coagulation factors by measuring the rate of fibrin formation in vitro. The primary outcome of these assays is the clotting time, which is traditionally measured in seconds from the addition of an activator or "starting agent" such as Ca 2+ The time from ions to the sample or sample / reaction mixture until a fibrin clot detectable in a manner similar to the coagulation assay is formed. Coagulation time is also a measure of the hemostatic potential of the sample, i.e., the coagulation ability, in which the influence of all procoagulant and anticoagulant factors and substances contained in the sample and determined by the corresponding assay begins to work. Coagulation time can also be determined by photometry by measuring the optical properties of the sample / reagent mixture, such as turbidity. In particular, the turbidity of the sample / reagent mixture is continuously measured, and the coagulation time is determined as the end point of the time-dependent change of the characteristic by means of the evaluation process described in, for example, US2019 / 0018030A1. Therefore, some coagulation in vitro diagnostic assays, particularly coagulation time measurements, can be classified as turbidity clot assays or generally classified as turbidity or scattered light determination. Some other coagulation in vitro diagnostic assays can be classified as colorimetric assays instead. For example, in a factor Xa assay, a peptide coupled to a detectable chromogenic or fluorescent label can be used, wherein the analyte, if present, resolves the chromogenic peptide into peptide and photometrically detectable label.

[0017] The typical example of this type of coagulation assay is prothrombin time (PT), which is also referred to as rapid test or thromboplastin time, activated partial thromboplastin time (APTT), thrombin time (TT), batroxobin clotting time (BT) or ecarin clotting time (ECT). These assays and their modifications are often used for screening defects (screening test, global test, search test) in the sub-range of coagulation system or for the activity measurement of individual factors. The coagulation system defects that can cause bleeding tendency or thrombosis tendency include, for example, (a) very low or very high coagulation factor concentration or activity, (b) mutant of coagulation factor, (c) very low or very high inhibitor concentration or activity, (d) mutant of inhibitor or (e) antibody for coagulation system element. On clinical working days, screening assays are mainly used for diagnosing hemolytic constitution or thrombotic constitution, and are also used for monitoring the therapy carried out using the medicine that affects the coagulation system. The determination of APTT, for example, is used on the one hand to screen for defects in the part of the coagulation cascade that begins in the "intrinsic pathway" and leads to the common pathway, which is composed of the coagulation factors FVIII, FIX, FXI, FXH, procarnosine releasing enzyme, HMW procarnosine, FV, FX, FII and fibrinogen. APTT results outside the normal range, i.e. prolonged clotting times, can indicate a defect in one or more of these factors, for example, a FVIII deficiency, also known as hemophilia A. On the other hand, APTT also reacts sensitively to the presence of anticoagulants such as heparin, and is therefore also used to monitor heparin therapy.

[0018] Photometric coagulation assays typically require one or more different types of reagents. "First reagent type" is a reagent required for the first reaction to occur in the early stages of the sample processing flow, and a second reagent type is typically required to complete the assay. According to one embodiment, the first reagent type is an incubation reagent, for example, a reagent that should remain in contact with the sample under certain conditions, for example, at a certain temperature for a certain time, so that the reaction is completed or reaches an acceptable degree of completion. A single assay may require one or more first type reagents, for example, added sequentially at different times of the reaction. An example of a first type of reagent is a reagent for determining coagulation factors and other coagulation parameters such as activated partial thromboplastin time (APTT). "Second reagent type" is a reagent required for a test liquid that has reacted with one or more reagents in order to complete the assay in the late stages of the sample processing flow; or a reagent that is sufficient to complete the assay without adding the first type of reagent. Therefore, the second reagent type may have the function of continuing the reaction of the first reagent type or terminating the reaction of the first reagent type or enabling the detection of the reaction of the sample with the first reagent type. The second reagent type can be the only reagent or the last reagent to be used in the assay before or during the detection. According to one embodiment, the second reagent type is a time-triggered reagent, also called a starting reagent, i.e., a reagent that triggers the time measurement starting from the moment the second reagent type has been added to the sample or sample / reaction mixture. The time-triggered reagent is a coagulation triggering reagent, for example, a saline solution such as a CaCl2 solution.

[0019] As used herein, the term "interference" refers to the effect of a substance present in a sample that changes the correct value of the result of a photometric in vitro diagnostic assay. As used herein, a sample showing interference refers to a sample having one or more interfering substances such as hemoglobin, bilirubin and lipids or other interfering substances, which can absorb or scatter light at wavelengths commonly used for photometric in vitro diagnostic assays. Further interfering substances can be drugs and medicaments or immunoglobulins present in the sample due to, for example, therapy or abuse. Sometimes, in the case of high concentrations of interfering substances, it can even be visually classified by the color of the sample.

[0020] The term "hemolysis" is defined as the release of intracellular components of red blood cells and other blood cells into the extracellular fluid and can be caused by different mechanisms. In vivo or in vitro hemolysis can cause the result to be significantly reduced or increased. During hemolysis, the intracellular concentration is 10 times higher than the extracellular concentration of the cell components in plasma / serum (e.g., potassium, lactate dehydrogenase, aspartate aminotransferase). The difference in serum analyte concentration between plasma and serum is also due to the lysis of blood cells (basically through platelets). Therefore, neuron-specific enolase, potassium and acid phosphatase are in higher concentrations in serum. Blood cell components can directly or indirectly interfere with analyte measurement. Adenylate kinase released from red blood cells can lead to an increase in creatine kinase and CK-MB activity, especially when the inhibitor of adenylate kinase in the assay mixture is insufficient. In contrast, the immunochemical quantification of CK-MB is not affected by adenylate kinase. The pseudoperoxidase activity of free hemoglobin is the cause of interference in the bilirubin process of Jendrassik and Groof, which causes interference by inhibiting the color development of diazo compounds. Proteases released from blood cells can reduce the activity of coagulation factors while increasing the formation of fibrin cleavage products.

[0021] "Bilirubin" can appear in plasma as a free molecule or covalently bound to albumin. In coagulation assays using turbidimetry, bilirubin concentrations exceeding 25 mmol / L lead to clinically relevant changes in the measured values ​​of antithrombin III. At higher bilirubin concentrations, interference will be significant in some coagulation assays. Oxidation under alkaline conditions leads to reduced absorption of bilirubin, which is the main reason for bilirubin interference in the modification of the Jaffé method without deproteinization. Under strongly acidic conditions, the absorption of conjugated bilirubin shifts to UV wavelengths and therefore interferes in the determination of phosphate by its reducing effect using the phosphomolybdate method. Bilirubin interferes with oxidase / peroxidase-based assays. Proportionally to its concentration, bilirubin can react with H2O2 in the test system, which systematically leads to lower results in enzymatic processes for measuring glucose, cholesterol, triglycerides, urate and creatinine. Bilirubin competitively interferes with the binding of dyes to albumin.

[0022] As used herein, the term "lipidemia" refers to the turbidity of a sample visible to the naked eye. This is often observed when the triglyceride concentration is above 300 mg / dl (3-4 mmol / L). The most common cause of turbidity is an increase in triglyceride concentration. Lipids interfere with almost all of the photometric quantities by light scattering and absorption. The apparent result may increase or decrease, depending on the blank process. At higher turbidities, measurements may not be possible due to the linearity limitations of the method.

[0023] The "effective interference level" can be determined by quantitatively determining any interfering substances, that is, by determining the presence and amount or absence of interfering substances through a so-called interference test. An example of an interference test is a "serum index" test. Quantitative index values ​​for the main interfering substances hemoglobin, bilirubin and lipids can be generated, expressed as H index (hemolysis), I index (icterus) and L index (lipidemia). This is usually done by the following process: aliquots of the sample are taken without dilution or more typically diluted to a preset ratio with a liquid other than the reagent, and photometrically measured at different wavelengths. In particular, lipidemia (L) is usually measured at a wavelength of 700 / 660nm because this range is not affected by hemolysis and icterus. Hemolysis (H) is usually measured at 600 / 570nm and corrected for absorption due to lipidemia. Jaundice (I) is usually measured at 505 / 480nm and corrected for absorption due to lipidemia and hemolysis. In order to make the interference test reliable and quantitative, it is important that the sample remains stable at least during the measurement process so that the photometric measurement occurs under constant or unchanged optical conditions. This means that in the case of dilution, the diluting liquid should be an inert liquid other than the solvent (i.e., non-reactive with the sample), such as water or a physiological solution, for example a saline solution such as a NaCl solution. Such tests and ways to perform the tests are well known in the art and are not described in further detail here.

[0024] The method for determining interference level using a photometric in vitro diagnostic assay disclosed herein comprises treating an aliquot of a sample with at least one reagent to obtain a sample / reagent mixture, and performing a photometric measurement on the sample / reagent mixture to obtain a result of the in vitro diagnostic assay, and determining a preliminary interference level by semi-quantitatively determining one or more interfering substances in the same sample / reaction mixture during the same photometric measurement. The method further comprises, only when a preliminary interference level above a predetermined threshold is determined, triggering an independent photometric measurement of another aliquot of the same sample, undiluted or diluted with a liquid other than the reagent, to determine an effective interference level by quantitatively determining the one or more interfering substances.

[0025] Therefore, only if a preliminary interference level above a predetermined threshold is determined during an in vitro diagnostic test on the same sample (ie, in the presence of the reagent), a quantitative interference test is performed and the effective interference level is determined.

[0026] Herein, in order to distinguish between specifically quantitative interference tests performed on independent sample aliquots and interference tests performed on samples / reaction mixtures undergoing photometric in vitro diagnostic assays and performed during photometric in vitro diagnostic assays, the term "interference test" is used for the former and the term "interference check" is used for the latter.

[0027] Unlike interference tests, interference checks are semi-quantitative and less reliable than interference tests because during the in vitro diagnostic assay, the optical conditions may be variable as the reaction occurs and progresses in the presence of the reagents. Furthermore, depending on the specific in vitro diagnostic assay, the sample dilution factor may be variable and may fall outside the optimal range. Furthermore, depending on the specific in vitro diagnostic assay, the wavelength used for the in vitro diagnostic assay and also for the interference check may differ at least in part from the optimal wavelength used in the interference test.

[0028] Therefore, by determining only a preliminary interference level, the interference check is used to provide an indication of the possible presence of interference, in which case confirmation by an interference test is required. Importantly, in the absence of a possible interference raised by the interference check, an interference test can be avoided, thereby minimizing the use of analytical resources and loss of throughput, minimizing costs, minimizing time to results, without compromising the quality of the results, and also avoiding risky decisions by the user.

[0029] The term "trigger" is used herein to mean either a fully automatic process that is automatically initiated and executed or an automatic alarm or warning that prompts manual intervention by a user, for example, for confirmation and / or for initiating a process that is then automatically executed.

[0030] According to one embodiment, the method comprises predetermining method suitability and / or method suitability scales for each in vitro diagnostic assay based on sample and / or reagent and / or assay-specific characteristics, which in vitro diagnostic assay can be performed by an in vitro diagnostic analyzer.

[0031] The term "method suitability" refers in particular to the assay-specific expectation of determining a preliminary interference level by an interference check with sufficient confidence to exclude the need for an interference test or to determine the need for an interference test. The higher the confidence, the higher the method suitability for a particular assay. However, for some assays, the confidence may be insufficient and the method is therefore not suitable; for other assays, it is also possible to determine a level of method suitability based on the confidence.

[0032] According to one embodiment, the method comprises predetermining the method suitability and / or the method suitability level for each in vitro diagnostic assay based on the sample to reagent volume ratio and / or the reagent type and / or the sample type and / or the wavelength of light used.

[0033] According to one embodiment, the method suitability and / or position in the method suitability hierarchy is proportional to the sample to reagent volume ratio, with the higher the sample to reagent volume ratio, the higher the method suitability, at least up to a predefined maximum sample to reagent volume ratio. In particular, depending on the specific sample to volume ratio of a particular assay, if the sample is too diluted by the reagent, the method may not be applicable.

[0034] According to one embodiment, the method comprises predetermining a threshold value for the preliminary interference level, said threshold value being assay-specific and applicable only to the in vitro diagnostic assay for which the method is applicable.

[0035] As used herein, whether referring to an interference check or an interference test, the term "threshold" refers to an upper limit of the concentration of one or more interfering substances, above which the accuracy of the in vitro diagnostic test results may not be guaranteed. For each interfering substance, the concentration value can be normalized relative to a reference value and can be expressed as an index value in the range of, for example, 0 to 100. For example, with respect to hemoglobin (H), an H index value of 100 can correspond to 1300 mg / dL hemoglobin; with respect to bilirubin (I, representing jaundice), an I index value of 100 can correspond to 66 mg / dL bilirubin; with respect to lipids (L), an L index value of 100 can correspond to 2000 mg / dL lipids.

[0036] Therefore, the threshold value may also be expressed as an acceptable maximum concentration or indirectly as an acceptable maximum index value, usually below 100, and may be different for different in vitro diagnostic assays and / or for different interference checks and interference tests, respectively.

[0037] According to one embodiment, the method comprises determining whether a plurality of different in vitro diagnostic assays are planned for the same sample, and positively prioritizing the planned in vitro diagnostic assays according to the method suitability level from highest to lowest or according to the assay specificity threshold from highest to lowest. In this way, a higher confidence in the indication provided by the interference check can be achieved. Moreover, if the corresponding thresholds are different, by starting with an assay associated with a higher threshold, it is eventually possible to release at least a portion of the results of those assays whose preliminary interference level is below the corresponding assay specificity threshold but above the threshold of other assays in the same series.

[0038] According to one embodiment, if a preliminary interference level is determined to be above at least one of the predetermined assay-specific thresholds of planned assays from the same sample, the method comprises at least preventing further execution of the in vitro diagnostic assay for which the assay-specific threshold is exceeded, and at least as long as the effective interference level is not determined to be below the corresponding predetermined threshold. If the effective interference level determined by the triggered interference test is below the preliminary level determined by the interference check and below the threshold predetermined for the interference test, further execution of in vitro diagnostic assays using the same sample may be restarted, at least restarting one or more assays for which the threshold is above the effective interference level.

[0039] According to one embodiment, the method comprises releasing the result of the in vitro diagnostic assay as long as the preliminary interference level is below a predetermined threshold, or, if the preliminary interference level is above a predetermined threshold, releasing the result of the in vitro diagnostic assay only after determining that the effective interference level is below a corresponding predetermined threshold; or marking the result of the in vitro diagnostic assay in another way.

[0040] According to one embodiment, the results of all in vitro diagnostic assays made using the same sample, including those whose preliminary interference levels ultimately fell below the corresponding thresholds, are released at the end only after determining that the effective interference level is below a predetermined threshold for all in vitro diagnostic assays and completing all planned in vitro diagnostic assays using the sample. In this case, all or none of the results may be released.

[0041] According to one embodiment, determining the preliminary interference level includes using the same wavelength of light as that used by the in vitro diagnostic assay. If more wavelengths are available than required for the specific in vitro diagnostic assay, for example, because they are used in other in vitro diagnostic assays, the method may include selecting the most appropriate wavelength among those wavelengths that can be used to determine the preliminary interference level.

[0042] According to one embodiment, determining the preliminary interference level includes extrapolating the photometric measurements obtained during the in vitro diagnostic assay to the initial time when the sample / reagent mixture was formed or the reaction started. This is because, during the in vitro diagnostic assay, as the reaction occurs and progresses in the presence of the reagent, the optical conditions can be variable. By extrapolating the photometric measurements obtained during the in vitro diagnostic assay to the initial time when the sample / reagent mixture was formed or the reaction started, this variation can be taken into account and a more accurate value can be assessed that is closer to the effective value in the absence of the reagent but using the same dilution factor.

[0043] The term "photometric measurements obtained during an in vitro diagnostic assay" refers to the same measurement data obtained from a photometric in vitro diagnostic assay and not to additional data. In particular, at least a portion of these data may be for example for only some wavelengths (if wavelengths exceeding those required for the interference check are used for the in vitro diagnostic assay), or for some selected wavelengths that are more suitable for the interference check, and / or only a subset of the data obtained, for example, at the initial stage of the photometric measurement.

[0044] Also disclosed herein is an in vitro diagnostic analyzer.

[0045] "In vitro diagnostic analyzer" is a laboratory automation instrument, which is specially used to analyze samples for in vitro diagnosis. According to the needs and / or according to the desired laboratory workflow, the in vitro diagnostic analyzer can have different configurations. By coupling multiple devices and / or modules together, additional configurations can be obtained. "Module" is a working unit with a dedicated function, which is usually smaller than the entire clinical diagnostic system. This function can be an analytical function, but it can also be a pre-analysis function or a post-analysis function, or it can be an auxiliary function of any of the pre-analysis function, the analysis function or the post-analysis function. In particular, the module can be configured to cooperate with one or more other modules for performing a dedicated task of the sample processing workflow, for example, by performing one or more pre-analysis steps and / or analysis steps and / or post-analysis steps. Therefore, the in vitro diagnostic analyzer may include an analytical device or a combination of any such analytical devices with a corresponding workflow, wherein the pre-analysis module and / or the post-analysis module can be connected to a separate analytical device or can be shared by multiple analytical devices. In an alternative, the pre-analysis function and / or the post-analysis function can be performed by a unit integrated in the analytical device. In vitro diagnostic analyzers may include functional units such as liquid handling units for pipetting and / or pumping and / or mixing samples and / or reagents and / or system fluids, and functional units for sorting, storing, transporting, identifying, separating, detecting. Examples of in vitro diagnostic analyzers include clinical chemistry analyzers, immunochemistry analyzers, coagulation analyzers, hematology analyzers, molecular diagnostic analyzers. This list is not exhaustive.

[0046] The in vitro diagnostic analyzer disclosed herein comprises at least a sample unit, a reagent unit, a detection unit for photometric measurement of a sample of a sample / reagent mixture or a sample / liquid mixture, and a controller running a computer-readable program having instructions for performing operations associated with any of the above-described method embodiments.

[0047] According to one embodiment, the in vitro diagnostic analyzer is a coagulation analyzer or a clinical chemistry analyzer or a combination of both.

[0048] The term "controller" encompasses any physical or virtual processing device, in particular a programmable logic computer running a computer-readable program having instructions for performing operations according to an operation plan, in particular associated with performing a method for determining an interference level using a photometric in vitro diagnostic assay. The controller may be part of an in vitro diagnostic analyzer, or an independent logical entity that communicates with the in vitro diagnostic analyzer. In some embodiments, the controller may be integrated with a data management unit, may be composed of a server computer, and / or may be distributed among multiple in vitro diagnostic analyzers. The controller may also be configured to control the in vitro diagnostic analyzer so that the workflow and workflow steps associated with performing the in vitro diagnostic assay are performed by the in vitro diagnostic analyzer. In particular, the controller may communicate and / or operate in conjunction with a scheduler and / or a data manager so as to take into account incoming assay commands and / or received assay commands and a large number of predetermined process operations associated with performing the assay commands to perform the above-mentioned method steps.

[0049] Other and further objects, features and advantages will appear from the following description of exemplary embodiments and the accompanying drawings, which serve to explain the principles in more detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 An in vitro diagnostic analyzer and a method for determining interference levels using a photometric in vitro diagnostic assay performed by the in vitro diagnostic analyzer are schematically shown.

[0051] Figure 2 Schematically shows some predetermined Figure 1 Guidelines for assay-specific suitability of methods.

[0052] Figure 3 A method for predetermining an assay-specific interference level threshold only for an in vitro diagnostic assay for which the method is applicable is schematically shown.

[0053] Figure 4 Schematically shows Figure 1 A further aspect of the method is the situation where it is planned to perform a plurality of different in vitro diagnostic assays on the same sample.

[0054] Figure 5 Some aspects of the method steps regarding determining a preliminary interference level are shown.

[0055] The skilled person will appreciate that the elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, the size of some elements in the drawings may be magnified relative to other elements to help enhance understanding of the embodiments of the present disclosure. DETAILED DESCRIPTION

[0056] Figure 1An in vitro diagnostic analyzer 100 is schematically shown, which includes a sample unit 10, a reagent unit 20, a detection unit 30 for photometric measurement of a sample S1-4 of a sample / reagent mixture S1-4 / R1-4 or a sample / liquid mixture S1-4 / DL, and a controller 40 running a computer-readable program having instructions for performing operations related to a method for determining an interference level using a photometric in vitro diagnostic assay (IVD) implemented by the in vitro diagnostic analyzer 100. The detection unit 30 includes at least one light source 31, which is capable of emitting light of different wavelengths λ1-4. According to one embodiment, the light source 31 includes a plurality of light emitting diodes (LEDs), which are independently configured to emit light of a specific wavelength or light within a specific wavelength range. The detection unit 30 further includes at least one optical detector 32 and at least one detection position positioned between the light source 31 and the optical detector 32, wherein the detection position includes an optical absorption cell 33 or is configured to receive the optical absorption cell 33 for photometrically measuring the sample S1-4 of the sample / reagent mixture S1-4 / R1-4 or the sample / liquid mixture S1-4 / DL. The at least one detector 32 can be configured to receive light from one wavelength at a time, for example, by alternating or continuously switching between different wavelengths λ1-4 during the photometric measurement. Alternatively, the at least one detector 32 can be configured to distinguish between different wavelengths λ1-4 or be divided into multiple regions dedicated to detecting different wavelengths λ1-4. Figure 1 The number of elements shown, in particular the number of samples S1-4, reagents R1-4 or wavelengths λ1-4, is for illustration only and may be any number. In particular, the light source 31 is typically configured to emit light of multiple wavelengths, the number of wavelengths corresponding to at least the number of interferents for which the interference level is to be determined and possibly more, corresponding to at least the number of different types of in vitro diagnostic assays requiring different wavelengths. Typically, the greater the number of wavelengths that are available and used to determine the interference level using a photometric in vitro diagnostic assay, the more accurate and reliable the measured result can be.

[0057] Continue to refer to Figure 1, also shows a method for determining the interference level using a photometric in vitro diagnostic assay, the method comprising treating an aliquot of a sample S3 with at least one reagent R1 to obtain a sample / reagent mixture S3 / R1, and performing a photometric measurement on the sample / reagent mixture S3 / R1 to obtain the result of the in vitro diagnostic assay, and determining a preliminary interference level (interference check) by semi-quantitatively determining one or more interfering substances in the same sample / reaction mixture (S3 / R1) during the same photometric measurement. In this example, the one or more interfering substances are any one or more of hemoglobin, bilirubin, and lipid substances, and the interference check is a "HIL check", where "H" represents hemolysis causing hemoglobin to be released from the red blood cells of the sample, "I" represents jaundice in the case of high bilirubin levels in the sample, and "L" represents lipemia in the case of high lipid levels in the sample.

[0058] The method further comprises, only when a preliminary interference level above a predetermined threshold is determined, triggering an interference test for another aliquot of the same sample S3, undiluted or diluted with a liquid DL other than a reagent (indicated by a dashed line in the case of using a liquid DL), and in the case of such a HIL test, the interference test is an independent photometric measurement in order to determine the effective interference level by quantitatively determining one or more interfering substances. Given that the detection unit 30 used for the interference test can be the same as the detection unit 30 used for the interference check, the most suitable wavelengths λ1, λ3, λ4 among those available λ1-λ4 can be used, which most suitable wavelengths may be different from those used for the IVD assay and the wavelengths used for the interference check.

[0059] Reference Figure 1 method, Figure 2Schematically illustrated are some criteria for pre-determining the suitability and / or method suitability level of each in vitro diagnostic assay for which the in vitro diagnostic analyzer is configured to perform these in vitro diagnostic assays. In particular, the method suitability or the position of a particular in vitro diagnostic assay in the method suitability level can be based on the sample type, e.g., whole blood, serum, plasma or other blood derivatives, urine, etc.; and / or based on the actual type, e.g., whether it is an incubation reagent that does not substantially change the photometric conditions or whether it is a starting reagent or triggering reagent that causes the start of a reaction that substantially changes the photometric conditions, or based on the inherent photometric properties of the reagent or reagent mixture itself (photometric background signals due to the use of reagents alone, e.g., inherent reagent turbidity); and / or based on assay-specific characteristics, such as a combination of sample type and one or more reagent types, the type of detection (e.g., turbidimetry, scatter photometry, colorimetry), reaction speed, etc. According to one embodiment, the method suitability and / or method suitability level of each in vitro diagnostic assay is pre-determined based on the volume ratio of sample to reagent. In particular, the method suitability is related to the volume ratio V of the sample to the reagent. S / V R The volume ratio of the sample to the reagent V is proportional to S / V R The higher V, the more applicable the method is, at least up to a predefined maximum sample to reagent volume ratio. In particular, as the sample becomes increasingly diluted below the ideal or optimal dilution factor, interference checks may become less frequent and less reliable, also depending on the detector sensitivity and the dynamic range of the assay. Moreover, since some reagents may have a certain inherent turbidity, when considering the sample to reagent volume ratio V S / V R This inherent turbidity may also play a role when the volume ratio of sample to reagent V S / V R The lower the reagent turbidity, the higher the method applicability.

[0060] According to one embodiment, the method suitability and / or method suitability level for each in vitro diagnostic assay is predetermined based on the wavelength of light used and / or which wavelengths are available on the in vitro diagnostic analyzer 100, which may be primarily biased toward performing in vitro diagnostic assays rather than interference checks. In particular, the closer the wavelength used for the in vitro diagnostic assay (λIVD assay) is to the wavelength most suitable for interference checks (λinterference checks), the higher the method suitability.

[0061] Figure 3Schematically illustrates a method for predetermining assay-specific interference level thresholds only for in vitro diagnostic assays for which the method is applicable. In particular, different IVD assays 1-n may be associated with different thresholds TS1-n (for preliminary interference levels) and different thresholds TS'1-n (for effective interference levels).

[0062] Predetermination of the method suitability or method suitability classes for different IVD assays and predetermination of threshold values ​​TS1-n, TS'1-n for IVD assays 1-n, respectively, is usually performed during assay development and the outcomes are associated with each respective assay and recorded in assay-specific curves. This is done by taking into account any one or more of the above criteria and empirically determining and verifying the range of suitability, in particular based on the assay-specific dilution factor, the wavelength used and the optical properties of the sample and reagents used in the particular assay, subtracting the background signal obtained, for example, by measuring the reagent used alone or diluted with the same dilution factor used in the assay but without the sample, comparing the preliminary interference level with the effective interference level, and confirming the reliable predictability of the interference check within a given range of values.

[0063] Figure 4 Schematically shows Figure 1 The method is also managed by the controller 40. In particular, the method includes determining whether a plurality of different IVD assays 1, 3, 4 are to be performed on the same sample S2, and positively determining the priority of the planned IVD assays 3, 4, 1 with respect to the preliminary interference level according to the method suitability from highest to lowest or according to the assay-specific thresholds TS 3, TS 4, TS 1 from highest to lowest. Thus, the method includes starting with IVD assay 3, which has the highest threshold TS3 and is also at a higher position in the method suitability hierarchy relative to the other IVD assays 4, 1, but in this example, the method is applicable to all planned IVD assays 1, 3, 4. It must be noted that being at a higher position in the method suitability hierarchy does not necessarily mean that the threshold of the preliminary interference level is higher.

[0064] According to one embodiment, if by performing the first IVD assay 3 it is determined that the preliminary interference level is below all of the assay-specific thresholds TS 3, TS 4, TS 1 predetermined for the planned IVD assays 3, 4, 1, respectively, from the same sample S2, the method comprises continuing to perform the remaining planned IVD assays 4, 1. If, on the contrary, the preliminary interference level is determined to be above at least one of the assay-specific thresholds TS 3, TS 4, TS 1 predetermined for the planned IVD assays 3, 4, 1, respectively, from the same sample S2, the method comprises triggering the interference test and preventing at least the further performance of the IVD assay 4 and / or IVD assay 1, whose assay-specific threshold TS4, TS1, respectively, is exceeded, and at least as long as the effective interference level is not determined to be below the respective predetermined threshold TS'4, TS'1.

[0065] For any of the planned IVD assays for the same sample S2, in case one or more of the predetermined effective interference level thresholds TS'3, TS'4, TS'1 are exceeded, the method may include preventing further execution of any of the remaining IVD assays 4, 1. Furthermore, the method may include marking any result of any performed IVD assay 3.

[0066] According to one embodiment, the method comprises releasing the result of the in vitro diagnostic assay as long as the preliminary interference level is below the predetermined threshold TS3, TS4, TS1 or, if the preliminary interference level is above the predetermined threshold TS3, TS4, TS1, releasing the result of the in vitro diagnostic assay only after determining that the effective interference level is below the corresponding predetermined threshold TS'3, TS'4, TS'1.

[0067] Figure 5Some aspects of the method steps for determining a preliminary interference level are shown. In particular, a conventional example of a typical result of an IVD coagulation assay is shown, wherein each curve consisting of a series of photometric measurement data over time (absorbance [optical density (OD) / cm] versus time [s]) is obtained using different wavelengths λ1, λ2, λ3, λ4, respectively. Given that the results of the coagulation IVD assay (e.g., clotting time) can be calculated from such a curve using known (e.g., disclosed in US2019 / 0018030A1) mathematical formulas and algorithms, the same data values ​​or at least a portion of them (e.g., some first measurement points) can be used to determine the preliminary interference level according to the method described herein. In particular, according to one embodiment, determining the preliminary interference level includes using the same wavelength of light as the in vitro diagnostic assay, or if more wavelengths are available, selecting any of the most suitable wavelengths λ1, λ3, λ4 among the available wavelengths λ1, λ2, λ3, λ4.

[0068] More specifically, according to one embodiment, determining the preliminary interference level comprises extrapolating the photometric measurements obtained during the in vitro diagnostic assay to the initial time of sample / reagent mixture formation or reaction initiation or averaging the data points measured closest to the initial time. Indeed, it can be noted that in this example, Figure 5 The curve in does not start at time 0. This may be the case when the sample and reagents are mixed with each other before the start of the photometric detection, for example at a location different from the detection location. Therefore, there may be a time delay between the start of the reaction and the start of the photometric measurement, and for interference checks, the most suitable data points are those that are as close as possible to the start of the reaction.

[0069] Interference checks may include (not shown) obtaining at least one blank photometric measurement by the in vitro diagnostic analyzer 100 for each wavelength λ1, λ3, λ4 used, at least once or at regular intervals, and possibly sharing the at least one blank photometric measurement with multiple assays of the same type. This may be obtained, for example, by measuring a reagent used alone or diluted with the same dilution factor as used in the corresponding IVD assay but without a sample and for each wavelength. Subsequently, the blank measurement may be subtracted from the measurement obtained during the IVD assay. Alternatively, the blank value may be taken from an assay curve determined under the same conditions during assay development.

[0070] In the foregoing description, many specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it is apparent to one of ordinary skill in the art that specific details are not required to practice what is taught herein. In other cases, well-known materials or methods are not described in detail to avoid obscuring the present disclosure.

[0071] In particular, modifications and variations of the disclosed embodiments are of course possible in light of the above description. It should therefore be understood that within the scope of the appended claims, the present disclosure may be practiced in a manner other than that specifically designed in the above examples.

[0072] In the foregoing description, references to "one embodiment," "an embodiment," "an example," or "an instance" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or instance is included in at least one embodiment. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an instance" appearing in various places throughout this specification do not necessarily all refer to the same embodiment or instance.

[0073] Furthermore, the particular features, structures or characteristics may be combined in any suitable combinations and / or subcombinations in one or more embodiments or examples.

Claims

1. A method for determining interference levels using a photometric in vitro diagnostic assay, the method comprising: - treating an aliquot of the sample with at least one reagent to obtain a sample / reagent mixture, and performing a photometric measurement of said sample / reagent mixture in order to obtain the result of said in vitro diagnostic assay, and determining a preliminary interference level by semi-quantitatively determining one or more interfering substances in the same sample / reagent mixture during the same photometric measurement, wherein determining said preliminary interference level comprises extrapolating the photometric measurement values ​​obtained during said in vitro diagnostic assay to the initial time of formation of the sample / reagent mixture or the start of the reaction or averaging the data points measured closest to the initial time, - Only when a preliminary interference level above a predetermined threshold is determined, an independent photometric measurement of another aliquot of the same sample, undiluted or diluted with a liquid other than a reagent, is triggered in order to determine the effective interference level by quantitatively determining the one or more interfering substances.

2. The method according to claim 1, wherein the one or more interfering substances are any one or more of hemoglobin, bilirubin, and lipid substances.

3. The method according to claim 2, comprising predetermining the method suitability and / or the method suitability grade for each in vitro diagnostic assay based on sample and / or reagent and / or assay specific characteristics.

4. The method according to claim 3, comprising predetermining the method suitability and / or the method suitability grade for each in vitro diagnostic assay based on the volume ratio of sample to reagent and / or the reagent type and / or the sample type and / or the light wavelength used.

5. The method according to claim 4, wherein the applicability of the method is proportional to the volume ratio of the sample to the reagent, and the higher the volume ratio of the sample to the reagent, the higher the applicability of the method, at least reaching a predefined maximum volume ratio of the sample to the reagent.

6. The method according to any one of claims 3 to 5, comprising predetermining a threshold value for the preliminary interference level, said threshold value being an assay-specific threshold value and being applicable only to the in vitro diagnostic assay for which the method is applicable.

7. The method according to any one of claims 3 to 5, comprising determining whether a plurality of different in vitro diagnostic assays are planned to be performed on the same sample, and in the affirmative, prioritizing the planned in vitro diagnostic assays according to the method suitability ranking from highest to lowest.

8. The method of claim 6, comprising determining whether a plurality of different in vitro diagnostic assays are planned for the same sample, and if so, prioritizing the planned in vitro diagnostic assays from highest to lowest according to the assay specificity threshold.

9. A method according to claim 8, wherein if a preliminary interference level is determined to be above at least one of the predetermined assay-specific thresholds of planned assays from the same sample, and as long as the effective interference level is not determined to be below the corresponding predetermined threshold, the method includes preventing further execution of the in vitro diagnostic assay for which the assay-specific threshold is exceeded.

10. The method of claim 1 , comprising releasing the result of the in vitro diagnostic assay as long as the preliminary interference level is below the predetermined threshold, or, if the preliminary interference level is above the predetermined threshold, releasing the result of the in vitro diagnostic assay only after determining that the effective interference level is below the corresponding predetermined threshold; or marking the result of the in vitro diagnostic assay in other cases.

11. The method of claim 1, wherein the photometric in vitro diagnostic assay is any one of turbidimetry, scattered photometry, and colorimetry.

12. The method of claim 11, wherein the photometric in vitro diagnostic assay is a coagulation assay or a clinical chemistry assay or a combination of both.

13. The method of claim 1, wherein determining the preliminary interference level comprises using the same wavelength of light as used for the in vitro diagnostic assay, or if more wavelengths are available, selecting any most appropriate wavelength among those available.

14. An in vitro diagnostic analyzer (100) comprising a sample unit (10), a reagent unit (20), a detection unit (30) for photometric measurement of a sample (S1-4) of a sample / reagent mixture or a sample / liquid mixture, and a controller (40) running a computer-readable program having instructions for performing operations associated with the method according to any one of claims 1 to 13.

15. The in vitro diagnostic analyzer (100) according to claim 14, wherein the analyzer (100) is a coagulation analyzer or a clinical chemistry analyzer or a combination of both.

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