Compositions and methods for improved creatinine measurement accuracy and uses thereof

Abstract

The present invention relates to compositions and methods for improved creatinine measurement accuracy and uses thereof. The present disclosure relates to electrochemical sensors for measuring creatinine and creatine in the blood of a patient. More particularly, the present disclosure relates to compositions and methods for improving the measurement accuracy of electrochemical sensors for measuring creatinine and creatine.

Description

[0001] This application is a divisional application of a patent application with application number 201980043652.4, application date June 3, 2019, and invention name “Compositions and methods for improving creatinine measurement accuracy and their uses”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 830,191, filed on April 5, 2019, the entire contents of which are incorporated by reference in their entirety. Technical Field

[0004] The present disclosure relates to electrochemical sensors for measuring creatinine and creatine in a patient's blood. More particularly, the present disclosure relates to compositions and methods for improving the measurement accuracy of electrochemical sensors for measuring creatinine and creatine. Background Art

[0005] The ability to accurately measure creatinine and creatine levels in a patient's blood is important. In particular, serum creatinine is an important indicator of renal health because it is excreted by the kidneys without change and can be easily measured. For example, elevated blood serum creatinine levels are late markers of chronic kidney disease, and are usually only observed when significant kidney damage has occurred. Chronic kidney disease refers to the gradual loss of kidney function. The kidney function is to filter waste and excess fluid from the blood, and these filtered waste and excess fluid are subsequently excreted in urine. When chronic kidney disease reaches an advanced stage (e.g., end-stage renal disease), dangerous levels of fluid, metabolites, electrolytes, waste, etc. can accumulate in the body. In the early stages of chronic kidney disease, there may be few signs or symptoms, and the progression of the disease may not become apparent until kidney function has been significantly impaired.

[0006] Creatinine / creatine in a sample (e.g., a patient's blood) can be measured by an electrochemical sensor. For example, a current creatinine sensor may include an enzyme-type biosensor containing three enzymes—creatinase, creatinase, and sarcosine oxidase—which catalyze the production of glycine, formaldehyde, and hydrogen peroxide from creatinine and water. These three enzymes can be fixed on the surface of a platinum electrode, and the final reaction product of hydrogen peroxide (H2O2) can then be electrochemically oxidized on a platinum electrode at a constant polarization potential and used to measure the creatinine and / or creatine levels in the patient's blood. However, in order to determine the creatinine and / or creatine concentration in a biological sample, the creatinine and creatine sensors need to be calibrated to determine their sensitivity. This can be done by measuring the current response of the creatinine and creatine sensors in a calibration solution with a predetermined concentration of creatinine and creatine. After determining the sensitivity of the creatinine and creatine sensors, the concentration of creatinine and creatine in any biological sample can be estimated by measuring the current signal of the sample and comparing the sensitivity of the measured creatinine and creatine sensors determined by the calibration process. Unfortunately, accurately measuring creatinine levels in biological samples is not an easy task for a variety of reasons. For example, sensor-to-sensor manufacturing variations that occur during biosensor production / manufacturing can cause variations in creatinine measurement accuracy that occur on a sensor-to-sensor or sensor device-to-sensor device basis. In addition, variations in the biological sample matrix can also create major challenges for accurately measuring creatinine levels. Accordingly, there is an urgent, unresolved need to identify and develop new methods to improve the calibration accuracy of biosensors for creatinine and / or creatine measurements. Summary of the invention

[0007] The present disclosure provides compositions and methods for improving the accuracy of creatinine and creatine in biosensors.

[0008] In one aspect, the present disclosure provides a method for improving the accuracy of a creatinine / creatine measurement system, the creatinine / creatine measurement system having a calibrated creatine sensor and a calibrated creatinine sensor, the method comprising the steps of: measuring a measured creatine sensor current signal (MΔI2) of a first biomatrix calibration solution (BMCS2) with the calibrated creatine sensor, the first biomatrix calibration solution (BMCS2) having a known concentration of creatine (CR_BMCS2) and a known concentration of creatinine (CREA_BMCS2); determining the measured The concentration of creatine in BMCS2 (MCR_BMCS2); comparing MCR_BMCS2 with CR_BMCS2 to determine the creatine sensor biomatrix correction factor (ΔCR); measuring the measured creatinine sensor current signal (MΔI2') of BMCS2 with a calibrated creatinine sensor; determining the measured concentration of creatinine in BMCS2 (MCREA_BMCS2); and comparing MCREA_BMCS2 with CREA_BMCS2 to determine the creatinine sensor biomatrix correction factor (ΔCREA).

[0009] In one embodiment, CR_BMCS2 and CREA_BMCS2 have stable values.

[0010] In one embodiment, the stable value is based on a stable ratio of creatine to creatinine in BMCS2.

[0011] In one embodiment, the stable value is based on the storage temperature of the BMCS2.

[0012] In one embodiment, BMCS2 comprises one or more biological matrix factors selected from: Ca ++ , HCO3 - , pH, pCO2, pO2, electrolytes, and metabolites.

[0013] In one embodiment, the ΔCR is applied to creatine measurements obtained from biological matrix samples.

[0014] In one embodiment, ΔCREA is applied to creatinine measurements obtained from biological matrix samples.

[0015] In one embodiment, the method further comprises the following steps: measuring a second measured creatine sensor current signal (M2ΔI2) of a second biomatrix calibration solution (BMCS3) with a calibrated creatine sensor, the second biomatrix calibration solution (BMCS3) having a known concentration of creatine (CR_BMCS3) and a known concentration of creatinine (CREA_BMCS3); determining the concentration of creatine in the measured BMCS3 (M2CR_BMCS3); comparing M2CR_BMCS3 with CR_BMCS3 to determine a second creatine sensor biomatrix correction factor (ΔCR'); measuring a measured creatinine sensor current signal (M2ΔI2') of BMCS3 with a calibrated creatinine sensor; determining the concentration of creatinine in the measured BMCS3 (M2CREA_BMCS3); and comparing M2CREA_BMCS3 with CREA_BMCS3 to determine a creatinine sensor biomatrix correction factor (ΔCREA').

[0016] In one embodiment, CR_BMCS3 and CREA_BMCS3 have stable values.

[0017] In one embodiment, the stable value is based on a stable ratio of creatine to creatinine in BMCS3.

[0018] In one embodiment, the stable value is based on the storage temperature of the BMCS3.

[0019] In one embodiment, BMCS3 comprises one or more biological matrix factors selected from: Ca ++ , HCO3 - , pH, pCO2, pO 2， electrolytes, and metabolites.

[0020] In one embodiment, ΔCR' is applied to the slope of creatine measurements obtained from a biological matrix sample.

[0021] In one embodiment, ΔCR, ΔCR', ΔCREA and ΔCREA' are applied to Slope 1 and Slope 2 of creatinine measurements obtained from a biological matrix sample.

[0022] In one embodiment, the stable ratio of creatine to creatinine is from about 1.5 to about 2.

[0023] In one embodiment, the stable ratio of creatine to creatinine is 1.5 to 2.

[0024] In one embodiment, BMCS2 or BMCS3 comprises about 2-5 mg / dL of creatine and about 1-3 mg / dL of creatinine, respectively.

[0025] In one embodiment, the stabilized value is stable for at least 8 months.

[0026] In one embodiment, Ca ++ The concentration of HCO3 is between about 0.4 and about 1.6 mg / dL and - The concentration is between about 10 and about 30 mg / dL.

[0027] In one aspect, the present disclosure provides a creatinine / creatine measurement system comprising: a calibrated creatine sensor; a calibrated creatinine sensor; one or more network interfaces communicating in a computer network; a processor coupled to the network interface and the creatine sensor and the creatinine sensor and adapted to perform one or more processes; and a memory configured to store processes executable by the processor, the processes being capable of operating when executed to: measure a measured creatine sensor current signal (MΔI2) of a first biological matrix calibration solution (BMCS2) with a calibrated creatine sensor, the first biological matrix calibration solution (BMCS2) having a known concentration (CR_B _BMCS2) and a known concentration of creatinine (CREA_BMCS2); determining the concentration of creatine in the measured BMCS2 (MCR_BMCS2); comparing MCR_BMCS2 with CR_BMCS2 to determine a creatine sensor biomatrix correction factor (ΔCR); measuring a measured creatinine sensor current signal (MΔI2') of BMCS2 with a calibrated creatinine sensor; determining the concentration of creatinine in the measured BMCS2 (MCREA_BMCS2); and comparing MCREA_BMCS2 with CREA_BMCS2 to determine a creatinine sensor biomatrix correction factor (ΔCREA).

[0028] "Control" or "reference" means a standard for comparison. In one aspect, as used herein, a sample or subject that is "changed compared to a control" is understood to have a level that is statistically different from that of a normal, untreated sample or control sample. Control samples include, for example, creatine solutions, creatinine solutions, etc. Methods for selecting and testing control samples are within the capabilities of those skilled in the art. Determining statistical significance is within the capabilities of those skilled in the art, for example, the standard deviation value of the mean that constitutes a positive result.

[0029] As used herein, "creatine (also known as 2-[amidino(methyl)amino]acetic acid, N-amidino-N-methylglycine or guanidinoacetic acid)" refers to an organic compound that generates energy for cells by recycling ATP by donating phosphate groups to convert adenosine diphosphate (ADP) back to adenosine triphosphate (ATP). Creatine has the following chemical structure:

[0030]

[0031] As used herein, "creatinine" refers to the byproduct of the enzymatic breakdown of creatine, and generally exists in two major tautomeric forms, which are shown below.

[0032]

[0033] The scope herein can be expressed as from "about" a specific value and / or to "about" another specific value. When such a scope is expressed, another aspect includes from a specific value and / or to another specific value. Similarly, when a value is expressed as an approximation by using the antecedent "about", it is understood that a specific value forms another aspect. It should also be understood that the endpoint of each range is significant relative to another endpoint and independently of another endpoint. It should also be understood that many values ​​are disclosed herein, and each value is also disclosed herein as the value of "about (near)" of the specific value in addition to the value itself. It should also be understood that throughout the application, data is provided in a variety of different formats, and the data represents the scope of any combination of endpoints and starting points and data points. For example, if a specific data point "10" and a specific data point "15" are disclosed, it should be understood that greater than, greater than or equal to, less than, less than or equal to, and equal to 10 and 15 are also considered to be disclosed between 10 and 15. It should also be understood that each unit (unit) between two specific units (units) is also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed. Ranges provided herein should be understood as shorthand for all of the values ​​within the range. For example, a range of 1 to 50 is understood to include any value, combination of values, or subrange in the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all intermediate decimal values ​​between the aforementioned integers, e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. For subranges, "nested subranges" extending from either end point of the range are specifically contemplated. For example, nested sub-ranges of the exemplary range 1 to 50 may include 1 to 10, 1 to 20, 1 to 30, and 1 to 40 in one direction, or 50 to 40, 50 to 30, 50 to 20, and 50 to 10 in the other direction.

[0034] Other features and advantages of the present disclosure will be apparent from the following description of its preferred embodiments and the claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the present disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described below. All disclosed foreign patents and patent applications cited herein are incorporated herein by reference. All other disclosed references, documents, manuscripts and scientific literature cited herein are incorporated herein by reference. In addition, materials, methods and examples are illustrative only and are not intended to be limiting.

[0035] Even if embodiments are described in different aspects of the present disclosure, it is contemplated that any one embodiment described herein may be combined with any other embodiment or embodiments, where applicable or not specifically denied.

[0036] These and other embodiments are disclosed and / or encompassed by the following Detailed Description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The following detailed description, which is provided by way of example and is not intended to limit the present disclosure to only the particular embodiments described, may be best understood in conjunction with the accompanying drawings, in which:

[0038] Figure 1A-1B Two graphs are shown depicting the deviation of creatinine measured by a whole blood creatinine biosensor relative to plasma creatinine on a chemistry analyzer. Figure 1A Creatinine measurements without correction are shown. Figure 1B Shown with Figure 1A Creatinine measurement of the same samples, but with two calibration solutions calibrated for creatine and creatinine sensitivity. DETAILED DESCRIPTION

[0039] The present disclosure is based at least in part on the discovery that one or more biomatrix calibration solutions can be used to generate creatine sensor biomatrix calibration factors and creatinine sensor biomatrix calibration factors. The present disclosure provides such creatine sensor biomatrix calibration factors and creatinine sensor biomatrix calibration factors, which can be applied to the measured creatine and / or creatinine values ​​in the biomatrix sample to correct for manufacturing variations from, for example, sensor to sensor and inhibitory factors present in the biomatrix sample (e.g., HCO3 - , Ca ++ , pH, etc.) activity measurement inaccuracy.

[0040] Overview

[0041] The creatinine sensor in the current creatine / creatinine system (e.g., GEM PAK kit) includes an enzyme-type biosensor containing three enzymes. These enzymes are immobilized on the surface of a platinum electrode. The creatinine detection system is based on a cascade reaction (Rx) of the following three enzymes:

[0042]

[0043]

[0044] The product hydrogen peroxide (H2O2) is then electrochemically oxidized at a platinum electrode under a constant polarization potential, and the current signal is proportional to the analyte concentration.

[0045] The presence of creatine in clinical samples necessitates an additional sensor for creatine measurement to calibrate the creatine response of the creatinine sensor.The creatine sensor comprises only reactions (2) and (3) of the above enzyme cascade.

[0046] Both creatine and creatinine sensors have a diffusion controlling membrane (also called outer membrane) on top of the enzyme layer. The diffusion controlling membrane limits the flow (flux) of creatinine and creatine substrates into the enzyme layer to ensure that the signal produced by hydrogen peroxide is proportional to the substrate concentration of the sample.

[0047] In order to determine the respective concentrations of creatinine and creatine in a biological sample(s), the creatinine and creatine sensors need to be calibrated to determine their respective sensitivities. This can be accomplished by comparing the current signals of the creatinine and creatine sensors in a calibration solution containing predetermined (e.g., known) concentrations of creatinine and creatine. After the sensitivity of the creatinine and creatine sensors has been determined, the concentrations of creatine and creatinine in any biological sample can be estimated by adjusting the measured readings with the results determined from the calibration process.

[0048] For example, a calibration system for a creatine sensor or biosensor may involve a 2-point calibration based on the following equation:

[0049] ΔI2 = [CR_CS2] * slope (Equation 1)

[0050] ΔI2 is the current signal measured by the creatine sensor in the first calibration solution (CS2). [CR_CS2] is the concentration of creatine in the first calibration solution (CS2). As discussed in detail below, CS2 can have a known concentration of creatine (CR_CS2), a known concentration of creatinine (CREA_CS2), and a stable ratio of creatine to creatinine, which allows the creatine sensor sensitivity (slope) to be established for the creatine sensor.

[0051] The calibration system for a creatinine sensor or biosensor can implement a 3-point calibration method. As the creatinine sensor provides a calibration solution containing both analytes of creatinine and creatine or a reading of both creatinine and creatine in a biological sample, the sensitivity of the creatinine sensor to creatinine (slope 1) or creatine (slope 2) can be determined from the following equations 2-5 according to the disclosure defined below. The present disclosure provides that two calibration solutions with different ratios of creatine / creatinine can be used for a 3-point calibration method.

[0052] 3-point Creatinine Sensor Calibration Equation:

[0053] ΔI2' = [CREA_CS2] * slope1 + [CR_CS2] * slope2 (Equation 2)

[0054] ΔI3′=[CREA_CS3]*slope1+[CR_CS3]*slope2 (Equation 3)

[0055] ΔI2' and ΔI3' are the current signals measured by the creatinine sensor in the first calibration solution (CS2) and the second calibration solution (CS3), respectively. CS3 may have an initial known creatine concentration (CR_CS3), an initial known creatinine concentration (CREA_CS3), and an unstable ratio of creatine to creatinine.

[0056] [CREA_CS2], [CREA_CS3], [CR_CS2] and [CR_CS3] represent the initial known concentrations of creatinine and creatine in calibration solutions CS2 and CS3, respectively. The sensitivity of the creatinine sensor to creatinine and creatine, slope 1 (sensor sensitivity to creatinine) and slope 2 (sensor sensitivity to creatine), can be obtained from equations 2 and 3:

[0057] Slope1 = ([CR_CS3]*ΔI2'-[CR_CS2]*ΔI3') / ([Creat_CS2]*[CR_CS3]-[Creat_CS3]*[CR_CS2])pA / mg / dL (Equation 4)

[0058] Slope2 = ([CREA_CS2]*ΔI3'–[CREA_CS3]*ΔI2') / ([Creat_CS2]*[CR_CS3]–[Creat_CS3]*[CR_CS2]) pA / mg / dL (Equation 5)

[0059] CS2 can be formulated at an optimally stable ratio of creatine / creatinine between about 1.5 and 2, while CS3 can be formulated at a different, unstable ratio of creatine / creatinine (about 10 to 70) that can change over time from the original ratio at the time of manufacture due to concentration changes during storage.

[0060] After proper calibration, the above-described creatinine measurement system can quantitatively measure the concentration of creatinine in a biological sample. However, there are several practical problems associated with sensor variation, which arise from typical manufacturing methods, calibration and variations specific to other analyzer runs, as well as biological sample matrix variations that present significant challenges for accurately measuring creatinine.

[0061] For example, the activity of many enzymes may be inhibited or affected by specific chemicals (e.g., ions or gases). For example, the above three enzyme system for converting creatinine to H2O2 is easily affected (e.g., due to inhibition or interference) by many common analytes that may be present in clinical chemistry assays, such as HCO3 - and Ca ++ . In addition, the system of three enzymes for converting creatinine to H2O2 is also sensitive to sample pH. Due to the difference in concentration of such analytes in biological samples between different patient samples or populations, errors may be introduced when measuring creatinine and / or creatine concentrations in biological samples. The prior art solutions to these problems include applying sensor measurement algorithms to address such effects. As an added complexity, sensor measurement systems are prone to manufacturing deviations that can produce sensor-to-sensor variability during the manufacturing process. For example, ordinary changes in sensor outer membrane composition or enzyme membrane thickness can produce significant errors, which originate from enzyme inhibition effects due to the relative diffusion of analyte (one or more) relative to inhibitory chemicals (one or more). Unfortunately, enzyme inhibition effects that can be found in biological samples and produce measurement errors are additive when combined with typical manufacturing variations from sensor to sensor; therefore, the combination of variable enzyme inhibition effects in the biological sample matrix and manufacturing variability from sensor to sensor can act in concert (e.g., synergistically) to produce larger measurement error differences.

[0062] Calibration matrix

[0063] It is common in clinical chemistry analyzers to provide multiple analyte determinations for a single sample measurement. In order to provide results for multiple analytes in a single measurement, up to three biomatrix calibration solutions with varying levels of analytes can be used for calibration and estimation of sensor sensitivity. For example, to calibrate the levels of pH and pCO2, pO2, electrolytes, or metabolites, two calibration reagent solutions with significantly different levels of each analyte can be used. However, to calibrate a creatinine sensor, three calibration reagent solutions with significantly varying levels of analytes can be used. The calibration reagent solution for calibrating a creatinine sensor according to the present disclosure contains one or more analytes in addition to creatinine and can be used to calibrate other types of sensors. Some of the one or more analytes present in these calibration reagent solutions may have an inhibitory effect on the ability of the creatinine sensor to measure creatinine. For example, the pH, HCO3 in these reagents may have an inhibitory effect on the ability of the creatinine sensor to measure creatinine. - and Ca ++ Levels can affect creatinine or creatine sensor calibration and may also have the potential to produce sensor-specific errors in calibration. The errors may be due to subtle variations from sensor to sensor and inhibition effects from the specific analytes mentioned above.

[0064] Biological sample matrix

[0065] The concentration of creatinine in the biological sample is related to the concentration of glucose (e.g., about 65 to about 95 mg / dL) or the concentration of an analyte that has an inhibitory effect on the sensor (e.g., Ca ++ The electrical signal of the sensor is typically very low (e.g., about 0.04 to about 1.10 mg / dL) compared to creatinine (e.g., about 4 to about 6 mg / dL or HCO3-: about 19 to about 26 mmol / L). The low concentration of creatinine in the biological sample, the loss of creatinine due to the presence of the diffusion-controlled outer membrane, and the conversion process of the three enzymes of the sensor all combine to produce a very low electrical signal. Conversely, the presence of relatively high concentrations of analytes that can have an inhibitory effect on creatinine measurement can have a significant impact on such a low electrical signal.

[0066] A prior art solution for this problem is to use a calibration solution. For example, in this method, the first step is to use the variable level of creatinine, creatine and inhibitors or interfering compounds present in the calibration solution to produce correction factors for each individual analyte. Disadvantageously, before obtaining a simple correction factor, this method requires many assumptions. In addition, the simultaneous interaction of multiple inhibitors or interfering compounds on enzyme activity is not considered. As a result, the validity of this prior art method is questionable due to the need for assumptions. Unfortunately, there is currently no good prior art solution to solve the practical problem of measuring the creatinine level in the biological sample that can show significant sample to sample biological matrix changes.

[0067] The present disclosure provides compositions and methods for correcting the errors that can be produced in the diagnostic cycle of the whole sensor calibration to the biological sample matrix measurement.Importantly, the technology herein provides a biomatrix calibration solution designed to match (or pairing) with common biological samples, and the common biological samples contain inhibitory analytes known to affect the activity of the system of three enzymes of creatinine / creatine.These solutions may have a predetermined creatinine and creatine concentration combined with the clinical reference range of the analyte with inhibitory or interfering effects on the enzyme used in the creatinine sensor (e.g., creatinase, creatinase, sarcosine oxidase, etc.), and the concentration is stable due to the stable creatine / creatinine ratio or optimized storage conditions.After installing and calibrating creatinine and / or creatine sensors, the calibration solution disclosed herein can be measured on creatinine and / or creatine sensors and the response of the calibration reagent and calibration solution measurement of both creatinine and creatine can be obtained and analyzed to identify the calibration factor specific to the sensor.These correction factors can be determined for all subsequent biological samples in the entire service life (lifetime use) of the sensor, without repeating this process at each sensor calibration.

[0068] The technology herein provides a creatinine measurement system that may include three main steps described in detail below: sensor calibration, establishment of correction factors, and sample measurement.

[0069] Sensor Calibration

[0070] The creatinine measurement system contains both creatinine and creatine sensors. The sensors are periodically subjected to calibration solutions with predetermined creatinine and creatine concentrations throughout the sensor's service life. Once determined, these sensitivities can be used for subsequent sample measurements. In multi-analyte clinical chemistry analyzers (e.g., GEM PAK boxes), the calibration reagent solution may also contain HCO - , Ca ++ and pH, which are known to affect creatinine or creatinase sensors. Since all of these solutions are used as a variety of analytes (e.g., HCO3-, Ca ++ Because common calibration solutions (such as pH and pH) are used, they cannot all be formulated to perfectly match the biological sample matrix. Therefore, the sensor sensitivity obtained from the calibration process is different from the sensitivity measured in the biological sample matrix. In addition, such deviations are inconsistent from sensor to sensor because subtle variations may occur during the manufacturing process of the multi-layer sensor structure.

[0071] Creatinine / Creatine Calibration Solution

[0072] The technology herein provides one or more specific creatinine / creatine solutions to simulate biological sample matrices having analytes known to inhibit or interfere with creatinine or creatinase sensors.

[0073] The first calibration solution may have predetermined creatinine and creatine concentrations in a matrix having inhibitory / interfering factors, e.g., HCO3 - (e.g., at about 20 mM), Ca ++ (e.g., at about 0.8 mM), pH (e.g., at about 7.4), and pCO2 (e.g., at about 30 mmHg), or in HCO3 - (e.g., about 10 to about 30 mM), Ca ++ The concentrations of the samples are within the range of (e.g., about 0.4 to about 1.6 mM), pH (e.g., about 7.0 to 8.0), and pCO2 (e.g., about 15 to about 45 mmHg), which are concentrations close to those of common clinical sample matrices.

[0074] A second calibration solution similar to the biological matrix, but with different levels of creatinine and creatine, may also be provided.

[0075] These calibration solutions can be stored in sealed reagent bags or ampoules to maintain constant pCO2 and pH levels. These solutions can be buffered, supplemented with biocides, and kept at an optimal storage temperature to ensure reagent stability. These calibration solutions can be measured as samples during sensor installation and when the initial calibration process is completed.

[0076] Create separate sensor correction factors for creatinine and creatine

[0077] During sensor installation and after initial calibration, a creatinine / creatine calibration solution can be measured on each creatinine or creatine measurement system to establish sensor sensitivity. The measured creatinine and creatine concentrations from the sensor are compared to the predetermined creatinine and creatine levels of the calibration solution to establish correction factors for both creatinine and creatine sensors, respectively.

[0078] Alternatively, after sensor installation, two calibration solutions may be measured sequentially, which may provide a more accurate correction factor due to measuring two different levels of creatinine and creatine.

[0079] These correction factors provide the sensitivity deviation in the biological matrix relative to the sensitivity obtained in the calibration solutions for the specific creatinine and creatine sensors.

[0080] According to the technology herein, the accuracy of a creatinine / creatine measurement system having a calibrated creatine sensor and a calibrated creatinine sensor can be improved by: measuring a measured creatine sensor current signal (MΔI2) of a first biomatrix calibration solution (BMCS2) with a calibrated creatine sensor, the first biomatrix calibration solution (BMCS2) having a known concentration of creatine (CR_BMCS2) and a known concentration of creatinine (CREA_BMCS2); determining the concentration of creatine in the measured BMCS2 (MCR_BMCS2); comparing MCR_BMCS2 with CR_BMCS2 to determine a creatine sensor biomatrix correction factor (ΔCR); measuring a measured creatinine sensor current signal (MΔI2') of BMCS2 with a calibrated creatinine sensor; determining the concentration of creatinine in the measured BMCS2 (MCREA_BMCS2); and comparing MCREA_BMCS2 with CREA_BMCS2 to determine a creatinine sensor biomatrix correction factor (ΔCREA).

[0081] In order to provide a biological matrix correction value / factor, CR_BMCS2 and CREA_BMCS2 may have stable values. For example, such stable values ​​may be based on a stable ratio of creatine to creatinine in BMCS2, or based on the storage temperature of BMCS2.

[0082] According to the technology herein, the biological matrix correction solution disclosed herein may include, but is not limited to, selected from Ca ++ 、HCO3 - , pH, pCO2, pO2, other electrolytes and metabolites.

[0083] Once obtained, ΔCR can be applied to creatine measurements obtained from biological matrix samples, while ΔCREA can be applied to creatinine measurements obtained from biological matrix samples.

[0084] According to the techniques herein, the accuracy of a creatinine / creatine measurement system having a calibrated creatine sensor and a calibrated creatinine sensor can be further improved by including the following additional steps: measuring a second measured creatine sensor current signal (M2ΔI2) of a second biological matrix calibration solution (BMCS3) having a known concentration of creatine (CR_BMCS3) and a known concentration of creatinine (CREA_BMCS3) with the calibrated creatine sensor; determining the measured BMCS3 The concentration of creatine in BMCS3 (M2CR_BMCS3); comparing M2CR_BMCS3 with CR_BMCS3 to determine a second creatine sensor biomatrix correction factor (ΔCR'); measuring the measured creatinine sensor current signal (M2ΔI2') of BMCS3 with a calibrated creatinine sensor; determining the concentration of creatinine in the measured BMCS3 (M2CREA_BMCS3); and comparing M2CREA_BMCS3 with CREA_BMCS3 to determine the creatinine sensor biomatrix correction factor (ΔCREA').

[0085] As discussed above for the first biological matrix calibration solution, CR_BMCS3 and CREA_BMCS3 can have stable values ​​based on a stable ratio of creatine to creatinine in BMCS3 or a storage temperature of BMCS3 (eg, 4° C.).

[0086] Once obtained, ΔCR' can be applied to the slope of creatine measurements obtained from biological matrix samples, while ΔCR, ΔCR', ΔCREA, and ΔCREA' can be applied to Slope 1 and Slope 2 of creatinine measurements obtained from biological matrix samples.

[0087] In an embodiment of the present disclosure, the stable ratio of creatine to creatinine is from about 1.5 to about 2, or from 1.5 to 2.

[0088] In an embodiment of the present disclosure, BMCS2 or BMCS3 may include about 2-5 mg / dL of creatine and about 1-3 mg / dL of creatinine, respectively.

[0089] According to the techniques herein, the stable values ​​of the above biological matrix calibration solutions can be stable for at least 8 months.

[0090] In an embodiment of the present disclosure, Ca ++ The concentration of HCO is between about 0.4 and about 1.6 mmol / L and HCO 3- The concentration is between about 10 and about 30 mmol / L.

[0091] Measurement of creatinine / creatine in biological samples

[0092] For each patient's sample, the current signal is measured on the creatinine and creatine sensors, and then the sensitivity from the most recent calibration is used to estimate the creatinine and creatine concentrations in the patient's sample. Correction factors can then be applied to the measured concentrations to generate the final creatinine and creatine measurements.

[0093] Alternatively, the correction can be applied to the raw sensitivity obtained from the calibration process. In this method, the correction factor obtained from the calibration solution is directly applied to the sensitivity obtained from the most recent sensor calibration. The sample creatinine and creatine concentrations are then estimated from the sample current signal and the corrected sensitivity.

[0094] Reagent test kit

[0095] The present disclosure also provides kits containing reagents of the present disclosure for use in the methods of the present disclosure. The kits of the present disclosure may include one or more containers containing reagents of the present disclosure (e.g., creatine, creatinine, etc.), and / or may include reagents in one or more calibration solutions containing an analyte, e.g., HCO3 - and Ca ++ In addition, the kits of the present disclosure may also include calibration solutions adjusted to a plurality of different pH levels. In some embodiments, the kits further include instructions for use according to the methods of the present disclosure. In some embodiments, these instructions may include instructions on how to apply the reagents / solutions to a sensor (e.g., a creatine sensor, a creatinine sensor, etc.), and how to calculate variables of interest (e.g., biomatrix factors such as Ca) according to any of the methods of the present disclosure. ++ Correction factor, HCO3 - Correction factors, pH correction factors, pCO2 correction factors, pO2 correction factors, electrolyte(s) correction factors, metabolite(s) correction factors, etc.). In some embodiments, the instructions include instructions on how to install and calibrate a measurement system as disclosed herein.

[0096] The instructions typically include information regarding reagent / solution concentrations, reagent / solution ratios (e.g., creatine / creatinine ratios), shelf life, etc. The instructions provided in the kits of the present disclosure are typically written instructions on a label or package insert (e.g., a paper included in the kit), but machine-readable instructions (e.g., instructions on a magnetic or optical storage disk) are also acceptable.

[0097] The label or package insert indicates that the reagent / solution can be used to calibrate any of a variety of creatine and / or creatinine sensors for use with a measurement system as described herein.Instructions can be provided for practicing any of the methods described herein, for example, to install and calibrate a measurement system.

[0098] The kits of this disclosure are in suitable packaging. Suitable packaging includes, but is not limited to, vials, ampoules, bottles, cans, flexible packaging (e.g., sealed Mylar or plastic bags), etc. It is also contemplated that the packaging is used in combination with a specific device, such as the GEM Premier whole blood analyzer class (Instrumentation Laboratory, Bedford, MA). In certain embodiments, at least one active agent in the reagent or solution is creatine and / or creatinine.

[0099] The kit may optionally provide additional components (ingredients), such as buffers and interpretative information. Generally, the kit comprises a container and a label or package insert (s) on or associated with the container.

[0100] The practice of the present disclosure employs, unless otherwise indicated, conventional techniques of chemistry, molecular biology, microbiology, recombinant DNA, genetics, immunology, cell biology, cell culture, and transgenic biology, which are within the skill of the art. See, for example, Maniatis et al., 1982, Molecular Cloning (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY); Sambrook et al., 1989, Molecular Cloning, Second Edition (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY); Sambrook and Russell, 2001, Molecular Cloning, Third Edition (Cold Spring Harbor Laboratory Press, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY); Harbor, NY); Ausubel et al., 1992), Current Protocols in Molecular Biology (John Wiley & Sons, including periodic updates); Glover, 1985, DNA Cloning (IRL Press, Oxford); Anand, 1992; Guthrie and Fink, 1991; Harlow and Lane, 1988, Antibodies, (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY); Jakoby and Pastan, 1979; Nucleic Acid Hybridization (BDHames&S.J.Higginseds.1984); Transcription And Translation (BDHames&S.J.Higgins eds.1984); Culture Of Animal Cells (RIFreshney, Alan R.Liss, Inc., 1987); Immobilized CellsAnd Enzymes (IRL Press, 1986); B.Perbal, A Practical Guide To Molecular Cloning (1984); the treatise, Methods In Enzymology (Academic Press, Inc., NY); GeneTransfer Vectors For Mammalian Cells (JHMiller and MPCalos eds., 1987, ColdSpring Harbor Laboratory); Methods In Enzymology, Volumes 154 and 155 (Wu et al. eds.), Immunochemical Methods In Cell And Molecular Biology (Mayer and Walker, eds., Academic Press, London, 1987); Handbook Of Experimental Immunology, Volumes I-IV (DMWeir and CC Blackwell, eds., 1986); Riott, Essential Immunology, Sixth Edition, Blackwell Scientific Publications, Oxford, 1988; Hogan et al., Manipulating the MouseEmbryo, (Cold Spring Harbor Laboratory) Press, Cold Spring Harbor, NY, 1986); Westerfield, M., The zebrafish book. A guide for the laboratory use of zebrafish (Danio rerio), (4th ed., Univ. of Oregon Press, Eugene, 2000). .

[0101] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein may be used in practice or testing this disclosure, suitable methods and materials are described below. All publications, patent applications, patents and other references mentioned herein are incorporated herein in their entirety by reference. In the event of a conflict, this specification (including definitions) shall prevail. In addition, materials, methods and examples are illustrative only and are not intended to be limiting.

[0102] The present disclosure also relates to computer systems involved in implementing methods of the present disclosure related to both computing and sequencing (ordering).

[0103] Computer systems (or digital devices) can be used to receive, transmit, display and / or store results, analyze results, and / or generate results and analysis reports. Computer systems can be understood as logical devices that can read instructions from media (e.g., software) and / or network ports (e.g., from the Internet), which can be optionally connected to a server with fixed media. Computer systems can include one or more CPUs, disk drives, input devices (e.g., keyboards and / or mice), and display devices (e.g., monitors). Data communications, such as the transmission of instructions or reports, can be transmitted to a local server or a remote location via a communication medium. The communication medium can include any means of transmitting and / or receiving data. For example, the communication medium can be a network connection, a wireless connection, or an Internet connection. Such a connection can provide communication through the World Wide Web. It is envisioned that data related to the present disclosure can be transmitted via such a network or connection (or any other suitable means for transmitting information, including but not limited to mailing physical reports, such as printouts) for reception and / or by a receiver for review. The receiver can be, but is not limited to, a single or electronic system (e.g., one or more computers, and / or one or more servers). The computer system may be integrated with or separate and distinct from the creatinine / creatine biosensor system / device.

[0104] In some embodiments, the computer system may include one or more processors. The processor may be associated with one or more controllers, computing units, and / or other units of the computer system, or may be implanted in firmware as needed. If implemented in software, routines may be stored in any computer-readable memory, such as RAM, ROM, flash memory, disk, laser disk, or other suitable storage medium. Similarly, the software may also be transmitted to the computing device by any known transmission method, including, for example, communication channels, such as telephone lines, the Internet, wireless connections, etc., or transmitted to the computing device by removable media, such as computer-readable disks, flash drives, etc.

[0105] Various steps may be implemented as various blocks, operations, tools, modules, and techniques, which in turn may be implemented in hardware, firmware, software, or any combination of hardware, firmware, and / or software. When implemented in hardware (e.g., creatinine / creatine biosensor system / device), some or all of the blocks, operations, techniques, etc. may be implemented in, for example, a custom integrated circuit (IC), an application specific integrated circuit (ASIC), a field programmable logic array (FPGA), a programmable logic array (PLA), etc.

[0106] In the embodiments of the present disclosure, a client-server, relational database structure can be used. A client-server structure is a network structure in which each computer or process on the network is a client or server. A server computer is typically a powerful computer dedicated to managing a disk drive (file server), a printer (print server), or network traffic (network server). Client computers include PCs (personal computers) or workstations on which users run applications, as well as example output devices disclosed herein. Client computers rely on server computers to obtain resources, such as files, devices, and even processing power. In some embodiments of the present disclosure, the server computer handles all database functions. The client computer may have software that handles all front-end data management and may also receive data input from the user.

[0107] Machine-readable media that may include computer executable code may take a variety of forms, including but not limited to tangible storage media, carrier media, or physical transmission media. Non-volatile storage media include, for example, optical or magnetic disks, for example, any storage device in any computer (one or more), etc., such as can be used to implement a database, etc., as shown. Volatile storage media include dynamic memory, such as the main memory of such a computer platform. Tangible transmission media include coaxial cables; copper wire and optical fiber, including the wires that comprise a bus within a computer system. Carrier transmission media may take the form of electrical or electromagnetic signals, or the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer readable media thus include, for example: a floppy disk, a flexible disk, a hard disk, a magnetic tape, any other magnetic medium, a CD-ROM, a DVD or DVD-ROM, any other optical medium, a punched card tape, any other physical storage medium with a pattern of holes, a RAM, a ROM, a PROM and an EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave conveying data or instructions, a cable or connection conveying such a carrier wave, or any other medium from which a computer can read programming code and / or data. Many of these computer readable media forms may be involved in conveying one or more sequences of one or more instructions to a processor for execution.

[0108] The computer executable code of the present subject can be executed on any suitable device (including server, PC, or mobile device such as smart phone or tablet computer) that can include processor. Any controller or computer optionally includes a monitor, which can be a cathode ray tube ("CRT") display, a flat panel display (e.g., an active matrix liquid crystal display, a liquid crystal display, etc.), and other displays. The computer circuit is usually placed in a box, and the box includes a plurality of integrated circuit chips, such as a microprocessor, a memory, an interface circuit, etc. The box also optionally includes a hard disk drive, a floppy disk drive, a large capacity removable drive (e.g., a writable CD-ROM) and other common peripherals. An input device (e.g., a keyboard, a mouse or a touch sensitive screen) optionally provides input from a user. The computer may include appropriate software for receiving user instructions, in the form of a set of parameter fields entered by the user (e.g., in a GUI) or in the form of pre-programmed instructions (e.g., pre-programmed for various specific operations).

[0109] Reference will now be made in detail to the exemplary embodiments that illustrate the present disclosure. Although the present disclosure will be described in conjunction with the exemplary embodiments, it should be understood that this is not intended to limit the present disclosure to those embodiments. On the contrary, it is intended to cover substitutions, modifications, and equivalents that may be included within the spirit and scope of the present disclosure as defined by the appended claims.

[0110] The present invention includes the following aspects / embodiments / features in any order and / or in any combination:

[0111] 1. A method of improving the accuracy of a creatinine / creatine measurement system having a calibrated creatine sensor and a calibrated creatinine sensor, the method comprising:

[0112] measuring a measured creatine sensor current signal (MΔI2) of a first biomatrix calibration solution (BMCS2) with a calibrated creatine sensor, the first biomatrix calibration solution having a known concentration of creatine (CR_BMCS2) and a known concentration of creatinine (CREA_BMCS2);

[0113] determining the concentration of creatine in the measured BMCS2 (MCR_BMCS2);

[0114] MCR_BMCS2 was compared with CR_BMCS2 to determine the creatine sensor biomatrix correction factor (ΔCR);

[0115] The measured creatinine sensor current signal (MΔI2′) of BMCS2 was measured using a calibrated creatinine sensor;

[0116] determining the concentration of creatinine in the measured BMCS2 (MCREA_BMCS2); and

[0117] MCREA_BMCS2 was compared to CREA_BMCS2 to determine the creatinine sensor biomatrix correction factor (ΔCREA).

[0118] 2. The method of any preceding or following embodiment / feature / aspect, wherein CR_BMCS2 and CREA_BMCS2 have stable values.

[0119] 3. The method of any preceding or following embodiment / feature / aspect, wherein the stable value is based on a stable ratio of creatine to creatinine in BMCS2.

[0120] 4. The method of any preceding or following embodiment / feature / aspect, wherein the stable value is based on a storage temperature of the BMCS2.

[0121] 5. The method of any preceding or subsequent embodiment / feature / aspect, wherein BMCS2 comprises one or more biological matrix factors selected from: Ca ++ , HCO3 - , pH, pCO2, pO2, other electrolytes, and metabolites.

[0122] 6. The method of any preceding or following embodiment / feature / aspect, wherein the ΔCR is applied to creatine measurements obtained from a biological matrix sample.

[0123] 7. The method of any preceding or following embodiment / feature / aspect, wherein ΔCREA is applied to creatinine measurements obtained from a biological matrix sample.

[0124] 8. The method of any preceding or subsequent embodiment / feature / aspect, further comprising:

[0125] measuring a second measured creatine sensor current signal (M2ΔI2) of a second biomatrix calibration solution (BMCS3) having a known concentration of creatine (CR_BMCS3) and a known concentration of creatinine (CREA_BMCS3) with a calibrated creatine sensor;

[0126] determining the concentration of creatine in the measured BMCS3 (M2CR_BMCS3);

[0127] M2CR_BMCS3 was compared with CR_BMCS3 to determine the second creatine sensor biomatrix correction factor (ΔCR');

[0128] The measured creatinine sensor current signal (M2ΔI2′) of BMCS3 was measured using a calibrated creatinine sensor;

[0129] determining the concentration of creatinine in the measured BMCS3 (M2CREA_BMCS3); and

[0130] M2CREA_BMCS3 was compared to CREA_BMCS3 to determine the creatinine sensor biomatrix correction factor (ΔCREA').

[0131] 9. The method of any preceding or following embodiment / feature / aspect, wherein CR_BMCS3 and CREA_BMCS3 have stable values.

[0132] 10. The method of any preceding or following embodiment / feature / aspect, wherein said stable value is based on a stable ratio of creatine to creatinine in BMCS3.

[0133] 11. The method of any preceding or following embodiment / feature / aspect, wherein the stable value is based on a storage temperature of the BMCS3.

[0134] 12. The method of any preceding or subsequent embodiment / feature / aspect, wherein BMCS3 comprises one or more biological matrix factors selected from: Ca ++ , HCO3 - , pH, pCO2, pO2, other electrolytes, and metabolites.

[0135] 13. The method of any preceding or following embodiment / feature / aspect, wherein ΔCR' is applied to the slope of creatine measurements obtained from the biological matrix sample.

[0136] 14. The method of any preceding or following embodiment / feature / aspect, wherein ΔCR, ΔCR', ΔCREA and ΔCREA' are applied to Slope 1 and Slope 2 of creatinine measurements obtained from a biological matrix sample.

[0137] 15. The method of any preceding or following embodiment / feature / aspect, wherein the stabilized ratio of creatine to creatinine is about 1.5 to about 2.

[0138] 16. The method of any preceding or following embodiment / feature / aspect, wherein the stabilized ratio of creatine to creatinine is between 1.5 and 2.

[0139] 17. The method of any preceding or following embodiment / feature / aspect, wherein BMCS2 or BMCS3 comprises about 2-5 mg / dL of creatine and about 1-3 mg / dL of creatinine, respectively.

[0140] 18. The method of any preceding or following embodiment / feature / aspect, wherein said stabilized value is stable for at least 8 months.

[0141] 19. The method of any preceding or subsequent embodiment / feature / aspect, wherein Ca ++ The concentration of HCO3 is between about 0.4 and about 1.6 mg / dL and - The concentration is between about 10 and about 30 mmol / L.

[0142] 20. A creatinine / creatine measuring system comprising:

[0143] calibrated creatine sensor;

[0144] calibrated creatinine sensor;

[0145] One or more network interfaces for communicating in a computer network;

[0146] a processor coupled to the network interface and the creatine sensor and the creatinine sensor and adapted to perform one or more processes; and

[0147] A memory configured to store processes executable by a processor, the processes being capable of, when executed, operating to:

[0148] measuring a measured creatine sensor current signal (MΔI2) of a first biomatrix calibration solution (BMCS2) with a calibrated creatine sensor, the first biomatrix calibration solution having a known concentration of creatine (CR_BMCS2) and a known concentration of creatinine (CREA_BMCS2);

[0149] determining the concentration of creatine in the measured BMCS2 (MCR_BMCS2);

[0150] MCR_BMCS2 was compared with CR_BMCS2 to determine the creatine sensor biomatrix correction factor (ΔCR);

[0151] The measured creatinine sensor current signal (MΔI2′) of BMCS2 was measured using a calibrated creatinine sensor;

[0152] determining the concentration of creatinine in the measured BMCS2 (MCREA_BMCS2); and

[0153] MCREA_BMCS2 was compared to CREA_BMCS2 to determine the creatinine sensor biomatrix correction factor (ΔCREA).

[0154] 21. The creatinine / creatine measurement system of any preceding or following embodiment / feature / aspect, wherein said process when executed is further operable to:

[0155] measuring a second measured creatine sensor current signal (M2ΔI2) of a second biomatrix calibration solution (BMCS3) with a calibrated creatine sensor, the second biomatrix calibration solution having a known concentration of creatine (CR_BMCS3) and a known concentration of creatinine (CREA_BMCS3);

[0156] determining the concentration of creatine in the measured BMCS3 (M2CR_BMCS3);

[0157] M2CR_BMCS3 was compared with CR_BMCS3 to determine the second creatine sensor biomatrix correction factor (ΔCR');

[0158] The measured creatinine sensor current signal (M2ΔI2′) of BMCS3 was measured using a calibrated creatinine sensor;

[0159] determining the concentration of creatinine in the measured BMCS3 (M2CREA_BMCS3); and

[0160] M2CREA_BMCS3 was compared to CREA_BMCS3 to determine the creatinine sensor biomatrix correction factor (ΔCREA').

[0161] 22. The creatinine / creatine measurement system of any preceding or following embodiment / feature / aspect, wherein ΔCR, ΔCR', ΔCREA and ΔCREA' are applied to Slope 1 and Slope 2 of creatinine measurements obtained from a biological matrix sample.

[0162] Example

[0163] The present disclosure is further illustrated by the following examples, which should not be construed as limiting. All references and the contents of the disclosed patents and patent applications cited throughout this application are incorporated herein by reference. Those skilled in the art will recognize that the present disclosure can be practiced with modifications in disclosed structures, materials, compositions and methods, and these modifications are considered to be within the scope of the present disclosure.

[0164] Example 1: Bias table of whole blood creatinine samples measured by GEM PAK cartridges with and without biological matrix correction technique relative to plasma creatinine measured by a chemistry analyzer.

[0165] The bias (difference in creatinine measured between the GEM PAK and reference chemistry analyzers) of whole blood clinical samples calibrated with both solution matrices was minimized to meet clinical requirements.

[0166] In this study, each test kit contains a creatinine measurement system plus two external calibration solutions. The creatinine measurement system includes a creatinine sensor, a creatine sensor, three calibration solutions (CS1, CS2 and CS3) and two external biomatrix calibration solutions (BMCS2 and BMCS3). Two methods for establishing the creatine and creatinine concentrations of whole blood samples were studied: Option (a), no creatine and creatinine biomatrix corrections were applied to the samples measured by GEM PAK; and Option (b), creatine and creatinine in whole blood clinical samples were corrected based on correction factors, which were established by measuring BMCS2 and BMCS3 at the beginning of the service life of each PAK, and then by applying the correction factor to creatine and creatinine slopes throughout the service life. Figure 1A It is shown that option (a) is applied to creatinine and the bias in reported creatinine for all whole blood clinical samples is clearly negative with some scatter relative to the accepted clinical parameters (refer to data points in the form of blue diamonds relative to the dashed line). Figure 1B It was demonstrated that by applying option (b) to the creatinine sample algorithm, both the negative bias in the whole blood clinical samples and the dispersion of reported creatinine across the sample range were significantly reduced to meet the desired clinical criteria (still referring to the data points in the form of blue diamonds relative to the dashed line).

[0167] Incorporated by Reference

[0168] All documents cited or referenced herein, and all documents cited or referenced in documents cited herein, are incorporated by reference, along with any manufacturer's instructions, descriptions, product specifications, and product manuals for any products mentioned herein or in any document incorporated by reference herein, and may be used in the practice of the present disclosure.

[0169] Equivalent form

[0170] It should be understood that the detailed examples and embodiments described herein are given by way of example only, for illustrative purposes only, and are by no means considered to be limitations of the present disclosure. In view of this, various modifications or changes will be proposed by those skilled in the art, and are included within the spirit and scope of the present application and are considered to be within the scope of the appended claims. Other advantageous features and functions associated with the systems, methods, and processes of the present disclosure will be apparent from the appended claims. In addition, those skilled in the art will recognize or be able to determine, using only routine experiments, many equivalents of the specific embodiments of the present disclosure described herein. These equivalents are intended to be covered by the appended claims.

Claims

1. A method of improving the accuracy of a creatinine / creatine measurement system having a calibrated creatine sensor and a calibrated creatinine sensor, the method comprising: measuring a measured creatine sensor current signal (MΔI2) of a first biomatrix calibration solution (BMCS2) with a calibrated creatine sensor, the first biomatrix calibration solution having a known concentration of creatine (CR_BMCS2) and a known concentration of creatinine (CREA_BMCS2); determining the concentration of creatine in the measured BMCS2 (MCR_BMCS2); MCR_BMCS2 was compared with CR_BMCS2 to determine the creatine sensor biomatrix correction factor (ΔCR); The measured creatinine sensor current signal (MΔI2′) of BMCS2 was measured using a calibrated creatinine sensor; determining the concentration of creatinine in the measured BMCS2 (MCREA_BMCS2); and MCREA_BMCS2 was compared to CREA_BMCS2 to determine the creatinine sensor biomatrix correction factor (ΔCREA).

2. The method of claim 1, wherein CR_BMCS2 and CREA_BMCS2 have stable values.

3. The method of claim 2, wherein the stable value is based on a stable ratio of creatine to creatinine in BMCS2.

4. The method of claim 2, wherein the stable value is based on a storage temperature of the BMCS2.

5. The method of claim 1, wherein BMCS2 comprises one or more biological matrix factors selected from the group consisting of: Ca ++ , HCO3 - , pH, pCO2, pO2, other electrolytes, and metabolites.

6. The method of claim 1, wherein the ΔCR is applied to creatine measurements obtained from a biological matrix sample.

7. The method of claim 1, wherein ΔCREA is applied to creatinine measurements obtained from a biological matrix sample.

8. The method of claim 1, further comprising: measuring a second measured creatine sensor current signal (M2ΔI2) of a second biomatrix calibration solution (BMCS3) having a known concentration of creatine (CR_BMCS3) and a known concentration of creatinine (CREA_BMCS3) with a calibrated creatine sensor; determining the concentration of creatine in the measured BMCS3 (M2CR_BMCS3); M2CR_BMCS3 was compared with CR_BMCS3 to determine the second creatine sensor biomatrix correction factor (ΔCR'); The measured creatinine sensor current signal (M2ΔI2′) of BMCS3 was measured using a calibrated creatinine sensor; determining the concentration of creatinine in the measured BMCS3 (M2CREA_BMCS3); and M2CREA_BMCS3 was compared to CREA_BMCS3 to determine the creatinine sensor biomatrix correction factor (ΔCREA').

9. The method of claim 8, wherein CR_BMCS3 and CREA_BMCS3 have stable values.

10. The method of claim 9, wherein the stable value is based on a stable ratio of creatine to creatinine in BMCS3.

11. The method of claim 9, wherein the stable value is based on a storage temperature of the BMCS3.

12. The method of claim 8, wherein BMCS3 comprises one or more biological matrix factors selected from the group consisting of: Ca ++ , HCO3 - , pH, pCO2, pO2, other electrolytes, and metabolites.

13. The method of claim 1, wherein the ΔCR' is applied to the slope of creatine measurements obtained from the biological matrix sample.

14. The method of claim 8, wherein ΔCR, ΔCR', ΔCREA and ΔCREA' are applied to Slope 1 and Slope 2 of creatinine measurements obtained from a biological matrix sample.

15. The method of claim 3 or 10, wherein the stabilized ratio of creatine to creatinine is from about 1.5 to about 2.

16. The method of claim 3 or 10, wherein the stable ratio of creatine to creatinine is 1.5 to 2.

17. The method of claim 3 or 10, wherein BMCS2 or BMCS3 comprises about 2-5 mg / dL of creatine and about 1-3 mg / dL of creatinine, respectively.

18. The method of claim 2 or 9, wherein the stabilized value is stable for at least 8 months.

19. The method of claim 5 or 12, wherein Ca ++ The concentration of HCO is between about 0.4 and about 1.6 mg / dL and HCO 3- The concentration is between about 10 and about 30 mmol / L.

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