WO2020080482A1 - Method for assaying validity of renal function test result based on cystatin c content in blood - Google Patents

Abstract

The present invention provides: a method for assaying the validity of a renal function test result based on the cystatin c content in blood, the method comprising a step for measuring the D-serine content in the blood of a subject who has had a renal function test performed based on the cystatin C content in blood, a step for comparing the D-serine content with a prescribed threshold; and a step for determining the validity of the renal function test result based on the cystatin C content in blood; and a sample analysis system and program for implementing said method.

Description

Method for validating renal function test results based on cystatin C amount in blood

The present invention relates to a method for validating a renal function test result based on the amount of cystatin C in blood, a sample analysis system for carrying out the method, and a program.

The glomerular filtration rate (GFR) is used as an indicator of renal function. The glomerular filtration rate represents the volume of fluid that is filtered from blood in the glomerulus in one minute, and its international standard measurement method is inulin clearance. However, inulin clearance requires continuous infusion of inulin for 2 hours, multiple urine collections and blood collections, and accurate measurement, which imposes a heavy burden on subjects and practitioners. For this reason, although an international standard measurement method has been established, due to various medical circumstances in each country, on-site medical treatment may not be introduced and the glomerular filtration rate may be determined using a substitute marker. . In Japan, the measurement of GFR by inulin clearance was covered by insurance as a test in 2006, but it was only performed in limited situations, and in daily clinical settings, estimation formulas using other renal function markers were used. Is used. As described above, as an adverse effect of not using the inulin clearance, which is the gold standard for the amount of glomerular filtration, there is a problem that accurate determination of renal function and accompanying early detection of renal disease are difficult.

As a method for determining the amount of glomerular filtration that replaces inulin clearance, a method based on the clearance of substances other than inulin and a method based on the renal function marker value in blood have been developed. These are used for determining GFR by examining the correlation with inulin clearance, which is an international standard measurement method. Cystatin C, which is a widely used renal function marker, is superior in that it does not require administration of a substance from outside the body, and the estimated glomerular filtration rate (eGFR) is determined by a formula that combines age and sex information. Has been done.

The eGFR determined in this way is widely used in medical examinations and medical settings. However, eGFR is an index created for the purpose of screening for deterioration of renal function and for simple and objective evaluation in epidemiological studies comparing a large number of subjects, and the kidneys of individual patients. It is still recommended by the Japanese Nephrological Society to use inulin clearance with inulin for functional evaluation.

The reason is that the measurement range of Cystatin C is narrow in the first place. In a situation where renal function is highly deteriorated (for example, GFR30 or less), the increase in the amount of cystatin C in blood slows down and the deviation from the original GFR becomes large, so that accurate renal function evaluation is difficult in end-stage renal disease. is there. It is also known that the accuracy decreases depending on the physical constitution, steroids, the use of immune system drugs such as cyclosporine, and the condition of patients such as diabetes, hyperthyroidism, inflammation, hyperbilirubinemia, and hypertriglyceridemia. . As described above, if screening for renal function is performed based on the amount of cystatin or eGFR, there is a risk that false positives and false negatives will be determined.

It has been clarified that D-amino acids, which have been considered to be absent in the living body of mammals, are present in various tissues and have physiological functions. Further, among the D-amino acids in blood, the concentrations of D-serine, D-alanine, D-proline, D-glutamic acid, and D-aspartic acid varied in renal failure patients and were correlated with cystatin C, It has been shown that it can be used as a diagnostic marker for renal failure (Non-patent document 1, Non-patent document 2, Non-patent document 3, Non-patent document 4). Furthermore, an amino acid selected from the group consisting of D-serine, D-threonine, D-alanine, D-asparagine, D-alrosreonine, D-glutamine, D-proline and D-phenylalanine is used as an index for the pathological condition of kidney disease. Is disclosed (Patent Document 1). These documents disclose that the D-amino acid in the blood of a patient suffering from renal disease fluctuates as compared with a healthy person, and thus it is possible to diagnose renal disease using these fluctuations as an index. Has been done.
On the other hand, there is no description or suggestion that the glomerular filtration ability based on inulin clearance can be determined by the amount of D-amino acid in blood. In recent years, urinary L-FABP, blood NGAL, urinary KIM-1 and the like have been developed as markers for kidney disease, but even if they are markers for kidney disease, they do not always show glomerular filtration ability. It cannot be determined or estimated.

International Publication No. 2013/140785

In the health checkup, the amount of cystatin C in blood and the estimated glomerular filtration rate based on the amount of cystatin C in blood are calculated for the purpose of renal function test, but in the renal function test based on the amount of cystatin C in blood, False positives and false negatives may be included in the determination of the results due to the influence of the physique and the decrease in accuracy due to the narrow measurement range. The purpose of the present invention is to test such false positives and false negatives.

When the present inventors focused their attention on D-serine in blood and investigated the correlation with GFR (inulin clearance), surprisingly, it was found that the amount of cystatin C in blood is higher than that in blood currently widely used. The inventors have found that the amount of D-serine in the blood has a high correlation with GFR (inulin clearance), and have completed the present invention.

Therefore, the present invention relates to the following:
[1] A method for testing the validity of a renal function test result based on the amount of cystatin C in blood, comprising:
Measuring the amount of D-serine in the blood of a subject who has undergone a renal function test based on the amount of cystatin C in the blood,
Comparing the amount of D-serine with a predetermined threshold value,
Determining the adequacy of the results of a renal function test based on the amount of cystatin C in the blood.
[2] The method according to Item 1, wherein the method for testing the validity of the renal function test result determines false positive and / or false negative renal function test result based on the amount of cystatin C in blood.
[3] If the renal function test is performed by a renal function test based on the amount of cystatin C in blood in the determination step, and the amount of D-serine exceeds the threshold value, it is determined as a false positive, The method described in item 2.
[4] In the above-mentioned determination step, if the renal function test based on the amount of cystatin C in the blood determines that it is normal, and the amount of D-serine is lower than the threshold value, it is determined to be a false negative. The method described.
[5] The method according to any one of Items 1 to 4, wherein the D-serine amount and the blood cystatin C amount are measured in the same sample.
[6] The item according to any one of items 1 to 5, wherein the subject is a subject to which a drug of the immune system (steroids, tacrolimus, anti-CD20 antibody, cyclohexamide, MMF, cyclosporine, etc.) is administered. Method.
[7] The method according to any one of Items 1 to 6, wherein therapeutic intervention is performed on a subject determined to be false negative or true negative.
[8] The method according to item 7, wherein the therapeutic intervention is selected from the group consisting of lifestyle improvement, dietary guidance, blood pressure control, anemia control, electrolyte control, uremic toxin control, blood glucose control, immune control and lipid control. .
[9] As the therapeutic intervention, a diuretic, a calcium antagonist, an angiotensin converting enzyme inhibitor, an angiotensin receptor antagonist, a sympathetic blocker, an SGLT2 inhibitor, a sulfonylurea drug, a thiazolidine drug, a biguanide drug, an α-glucosidase inhibitor Drug, glinide drug, insulin drug, NRF2 activator, immunosuppressant, statin drug, fibrate drug, anemia treatment drug, erythropoietin drug, HIF-1 inhibitor, iron drug, electrolyte regulator, calcium receptor agonist, Administering to the subject at least one drug selected from the group consisting of a phosphorus adsorbent, a uremic toxin adsorbent, a DPP4 inhibitor, an EPA preparation, a nicotinic acid derivative, a cholesterol transporter inhibitor, and a PCSK9 inhibitor, The method according to item 7 or 8.
[10] A sample analysis system including a storage unit, an input unit, an analysis measurement unit, a data processing unit, and an output unit, which tests the validity of a renal function test result based on the amount of cystatin C.
The storage unit stores the threshold value of the amount of D-serine input from the input unit,
The storage unit stores the result of the renal function test based on the amount of cystatin C in the blood input from the input unit,
The analysis and measurement unit separates and quantifies D-serine in the blood sample,
The data processing unit compares the amount of D-serine with the threshold value of the amount of D-serine stored in the storage unit, and validates the result of the renal function test based on the amount of cystatin C in the blood stored in the storage unit. Judge,
The sample analysis system, wherein the output unit outputs the validity of the result of the renal function test based on the amount of cystatin C in blood.
[11] A sample analysis system, which includes a storage unit, an input unit, an analysis measurement unit, a data processing unit, and an output unit, and which tests the validity of a renal function test result based on the amount of cystatin C,
The storage unit stores the threshold value of the amount of D-serine input from the input unit,
The storage unit stores the result of the renal function test based on the amount of cystatin C in the blood input from the input unit,
The analysis and measurement unit separates and quantifies D-serine in the blood sample,
The data processing unit compares the amount of D-serine with the threshold value of the amount of D-serine stored in the storage unit, and validates the result of the renal function test based on the amount of cystatin C in the blood stored in the storage unit. Judge,
The sample analysis system, wherein the output unit outputs the validity of the result of the renal function test based on the amount of cystatin C in blood.
[12] The sample analysis system according to item 11, wherein the validity of the renal function test result is determined as false positive and / or false negative of the renal function test result based on the amount of cystatin C in blood.
[13] The determination is false positive if the renal function test based on the amount of cystatin C in the blood determines that the renal function is decreased, while the amount of D-serine is lower than the threshold value. The sample analysis system described in 1.
[14] Item 12, wherein the determination is determined to be normal by a renal function test based on the amount of cystatin C in blood, while a false negative is determined when the amount of D-serine is higher than the threshold value. Sample analysis system.
[15] The sample analysis system according to any one of Items 10 to 14, wherein the amount of D-serine and the amount of cystatin C in blood are measured in the same sample.
[16] A program for causing an information processing apparatus including an input unit, an output unit, a data processing unit, and a storage unit to determine the appropriateness of a result of a renal function test based on the amount of cystatin C in blood, which is as follows:
The threshold value of the amount of D-serine input from the input unit is stored in the storage unit,
The result of the renal function test based on the amount of cystatin C in the blood input from the input unit is stored in the storage unit,
The amount of D-serine in the blood sample input from the input unit is stored,
The amount of D-serine stored in the storage unit and the threshold value of the amount of D-serine are read out, compared in the data processing unit, and the result of the comparison is stored in the storage unit as to whether the amount exceeds or falls below the threshold value.
The result of the renal function test based on the amount of cystatin C in the blood stored in the memory unit and the result of the comparison are read, the validity of the result of the renal function test is determined, and the result is stored in the memory unit.
The program, which includes a command for causing the information processing apparatus to cause the output unit to output the stored validity.
[17] A program that causes an information processing apparatus including an input unit, an output unit, a data processing unit, and a storage unit to determine the validity of a result of a renal function test based on the amount of cystatin C in blood, which is as follows:
The threshold value of the amount of cystatin C in the blood input from the input unit is stored in the storage unit,
Store the amount of Cystatin C in the blood sample input from the input unit,
The threshold value of the amount of D-serine input from the input unit is stored in the storage unit,
The amount of D-serine in the blood sample input from the input unit is stored,
The amount of cystatin C in the blood stored in the storage unit and the threshold value of the amount of cystatin C in the blood are read out, compared by the data processing unit, and the renal function test result based on the amount of cystatin C is stored in the storage unit,
The amount of D-serine stored in the storage unit and the threshold value of the amount of D-serine are read out, compared in the data processing unit, and the result of the comparison is stored in the storage unit,
The result of the renal function test based on the amount of cystatin C in the blood stored in the memory unit and the result of the comparison are read, the validity of the result of the renal function test is determined, and the result is stored in the memory unit.
The program, which includes a command for causing the information processing apparatus to cause the output unit to output the stored validity.

INDUSTRIAL APPLICABILITY The present invention uses the amount of D-serine that has a higher correlation with GFR (inulin clearance) together with the determination of renal function based on the amount of cystatin C in the blood, and thus the validity of determining the renal function based on the amount of cystatin C in the blood. It becomes possible to judge the sex.

FIG. 1 is a graph showing a scatter diagram of D-serine amount (A) and cystatin C amount (B) in blood and GFR (inulin clearance) (body surface area corrected). FIG. 2 is a graph showing a scatter diagram of D-serine amount (A) and cystatin C amount (B) in blood and GFR (inulin clearance) (without body surface area correction). FIG. 3 is a graph showing a scatter diagram of the amount of D-serine (A) and the amount of cystatin C (B) in blood, and the body surface area (BSA). FIG. 4 shows a block diagram of the sample analysis system of the present invention. FIG. 5 is a flowchart showing an example of an operation for testing the validity of the renal function test result according to the program of the present invention.

The present invention relates to a method for validating renal function test results based on the amount of cystatin C in blood. More specifically, the assay method of the present invention comprises the following:
Measuring the amount of D-serine in the blood of a subject who has undergone a renal function test based on the amount of cystatin C in the blood,
Comparing the amount of D-serine with a predetermined threshold value,
Determining the validity of the results of the renal function test based on the amount of cystatin C in the blood.

In one aspect, a method of validating a renal function test result based on the amount of cystatin C in blood relates to a method of determining a false negative or false positive result of a renal function test result based on the amount of cystatin C in blood. . The step of determining false negative or false positive is determined to be false positive when the renal function test based on the amount of cystatin C in the blood determines that the renal function is decreased, while the amount of D-serine is lower than the threshold value. , Or a renal function test based on the amount of cystatin C in the blood, it was determined to be normal, but when the amount of D-serine was higher than the threshold value, it could be determined as a false negative.

In another aspect of the present invention, a method for testing the validity of a renal function test result based on the amount of cystatin C in the blood comprises determining whether the renal function test result based on the amount of cystatin C in the blood is a true negative or a true positive. It may be a method of doing. The step of determining true negative or true positive is determined to be true positive when the renal function test based on the amount of cystatin C in the blood determines that the renal function is decreased, while the amount of D-serine is higher than the threshold value. , Or a renal function test based on the amount of cystatin C in the blood, it was determined to be normal, but when the amount of D-serine was lower than the threshold value, it could be determined as a true negative.

In the present invention, D-serine used as an index is an optical isomer of L-serine, which is an amino acid that constitutes proteins. The amount of D-serine is strictly controlled in each tissue and blood mainly by metabolic enzymes such as serine racemase and D-amino acid oxidase, while in the case of renal damage, D-serine in blood is The amount varies.

In the present invention, the “amount of D-serine in blood” may refer to the amount of D-serine in a specific blood amount, or may be expressed as a concentration. The amount of D-serine in blood is measured as the amount in a sample obtained by subjecting collected blood to centrifugation, sedimentation, or pretreatment for analysis. Therefore, the amount of D-serine in blood can be measured as the amount in a blood sample derived from blood such as collected whole blood, serum, plasma and the like. As an example, in the case of analysis using HPLC, the amount of D-serine contained in a predetermined amount of blood is represented by a chromatogram, and the height, area, and shape of peaks are compared with standard products and analyzed by calibration. It can be quantified. The amount of D-serine in blood can be measured by comparison with a sample having a known D-serine concentration, and the concentration of D-serine in blood can be used as the amount of D-serine in blood. . In the enzymatic method, the amino acid concentration can be calculated by quantitative analysis using a standard curve.

The formula for the correction can be determined from, for example, the correlation with GFR (inulin clearance). It can be determined by substituting the D-serine amount of the subject into a formula or a graph calculated from the correlation between the inulin clearance and the D-serine amount in blood. The inulin clearance may be a body surface area-corrected inulin clearance or may be a body surface area-uncorrected inulin clearance. It can be selected according to which of the glomerular filtration ability before and after the body surface area correction is necessary.

The amount of D-serine can be measured by any method, for example, measurement using chiral column chromatography, measurement using an enzymatic method, and immunological analysis using a monoclonal antibody that identifies an optical isomer of an amino acid. It can be quantified by the method. The amount of D-serine in the sample in the present invention may be measured by any method known to those skilled in the art. For example, chromatographic methods and enzymatic methods (Y. Naga et al., Clinical Science, 73 (1987), 105. Analytical Biochemistry, 150 (1985), 238., A. D'Anielloetetal., ComparativeBiochemistry and Physiology Part B, 66 (1980), 319. Journal of Neurochemistry, 29 (1977), 1053., A. Berneman et al., Journal of Microbial & Biochemical Technology, 2 (2010), 139., W. G. Gutheil et al., Analytical Biochemistry, 287 (2000), 196., G. Molala et al., Methods in Molecular Biology, 794 (2012), 273., T. Ito et.al., Analytical Biochemistry, 371 (2007), 167 Etc.), antibody method (T.Ohgusuet et al., Analytical Biochemistry, 357 (2006), 15., etc.), gas chromatography (GC) (H. Hasegawa et.al., Journal Mass Spectrometry, 46 (2011) ), 502., M. C. Waldhier et al., Analytical and and Bioanalytical Chemistry, 394 (2009), 695., A. Hashimoto, T. Nishikawa et al., FEBS Letters , 296 (1992), 33., H. Bruckner and A. Schieber, Biomedical Chromatography, 15 (2001), 166., M. Junge et al., Chirality, 19 (2007), 228., M. C. Waldhier Et al., Journal of Chromatography A, 1218 (2011), 4537.), Capillary electrophoresis (CE) (H. Miao et al., Analytical Chemistry, 77 (2005), 7190., D. L. Kirschner et al., AnalyticalChemistry, 79 (2007), 736., F. Kitagawa, K. Otsuka, Journal of Chromatography B, 879 (2011), 3078., G. Thorsen and J. Bergquist, Journal of, Chromatography (2000), 389.), High Performance Liquid Chromatography (HPLC) (N. Nimura and T. Kinoshita, Journal of Chromatography, 352 (1986), 169., A. Hashimoto et al., Journal of Chromatography, 582 ( 1992), 41., H. Bruckner et al., Journal of Chromatography A, 666 (1994), 259., N. Nimura et al., Analytical Biochemistry, 315 (2003), 262., C. Muller et al., Journal of Chromatography A, 1324 (2014), 109., S. Einarsson et al., AnalyticalChemistry, 59 (1987), 1191., E. Okuma and H. Abe, Journal of Chromatography B, ), 243., Y. Gogami et al., Journal of Chromatography B, 879 (2011), 3259., Y. Nagata et al., Journal of Chromatography, 575 (1992), 147., S. A. Fuchs et al., Climical Chemistry, 54 (2008), 1443., D. Gordes et al., Amino Acids, 40 (2011), 553., D. Jin et al., Analytical Biochemistry, 269 (1999), 124., J. Z. Min et al., Journal of Chromatography B, 879 (2011), 3220., T. Sakamoto et al., Analytical and Bioanalytical Chemistry, 408 (2016), 517., W. F. Visser et , Journal of Chromatography A, 1218 (2011), 7130., Y. Xing et al., Analytical and and Bioanalytical Chemistry, 408 (2016), 141., K. Imai et al., Biomedical Chromatography, 106 ., T. Fukushima et al., Biomedical Chromat ography, 9 (1995), 10., R. J. Reischl et al., Journal of Chromatography A, 1218 (2011), 8379., R. J. Reischl and W. Lindner, Journal of Chromatography A, 1269 ), 262., S. Karakawa et al., Journal of Pharmaceutical and Biomedical Analysis, 115 (2015), 123.,, etc.).

The separation / analysis system for optical isomers in the present invention may combine a plurality of separation / analysis. More specifically, a sample containing a component having an optical isomer, together with a first liquid as a mobile phase, is passed through a first column packing material as a stationary phase to separate the components of the sample. Holding each of the components of the sample individually in a multiloop unit, each of the components of the sample held individually in the multiloop unit as a stationary phase with a second liquid as a mobile phase. A second column packing material having an optically active center through a channel to separate the optical isomers contained in each of the components of the sample, and the optical isomers contained in each of the components of the sample. The D- / L-amino acid amount in the sample can be measured by using the method for analyzing optical isomers, which comprises the step of detecting the body (specific characteristics). No. 4,291,628). In HPLC analysis, D- and L-amino acids were previously derivatized with fluorescent reagents such as o-phthalaldehyde (OPA) and 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F). Or N-tert-butyloxycarbonyl-L-cysteine (Boc-L-Cys) may be used to diastereomerize (Kenji Hamase and Kiyoshi Zaitsu, Analytical Chemistry, 53, 677-690 ( 2004)). Alternatively, the D-amino acid can be measured by an immunological method using a monoclonal antibody that recognizes an optical isomer of an amino acid, for example, a monoclonal antibody that specifically binds to D-serine, L-serine and the like. When the total amount of D-form and L-form is used as an index, it is not necessary to separate and analyze D-form and L-form, and amino acids can be analyzed without distinguishing between D-form and L-form. In that case as well, it can be separated and quantified by an enzyme method, an antibody method, GC, CE, and HPLC.

Cystatin C, which is an assay target in the present invention, is a protein having a molecular weight of 13 kDa that is produced at a constant rate from nucleated cells throughout the body, and is all decomposed in the kidney through reabsorption in the renal tubule after being filtered by the glomerulus. It The amount of cystatin C in blood or the amount of glomerular filtration estimated from the amount of cystatin C in blood is used as an index of renal function because it is removed from blood according to the amount of filtration. In Japan, an estimation formula based on inulin clearance has been developed. However, it is known that the amount of cystatin C in blood varies depending on the influence of the physique and the presence or absence of a disease or drug administration. In addition, the blood cystatin C level reached a peak when the renal function was significantly reduced, and even with a standard subject, a correct evaluation cannot be performed with a value of 30 mL / min / 1.73 m ² or less. It is also known.

As described above, although a problem has been reported regarding a renal function test based on the amount of cystatin C in the blood, from the results that have been widely used until now, the amount of cystatin C in the blood and / or the renal function test in the health checkup has been reported. Estimated glomerular filtration rate based on the amount of cystatin C in blood is often adopted. For example, in the case of the amount of cystatin C in the blood, the threshold value is 0.95 mg / L for men and 0.87 mg / L for women, and above that, renal function is impaired. It is determined that if it is below the threshold, it is determined to be normal. In addition, when using the estimated glomerular filtration rate, in Japan, the estimated glomerular filtration rate is calculated based on an estimation formula using inulin clearance as a standard, and 60.0 mL / min / 1.73 m ² is used as a threshold value. If it is below this threshold, it is determined that the renal function is lowered, and if it is above this threshold, it is determined to be normal. Regarding the amount of cystatin C in blood and the estimated amount of glomerular filtration, the threshold value indicating a decrease in renal function may be changed by a survey led by the academic society and is not intended to be captured by the above-mentioned numerical values. Not only the amount of cystatin C in the blood, which is directly affected by physique, but also the estimated glomerular filtration rate corrected for age and sex, a special subject who suffers from a disease or is given a drug Then there will be false positive and false negative problems. Since the results of primary screening such as medical examinations include false negative results, there is a reality that early kidney disease is overlooked. Since renal function cannot be expected to be recovered once it is basically lost, it is preferable to judge renal function in early renal diseases without missing a false negative. In addition, if false positives are included, the subject usually undergoes a secondary test, where kidney disease is comprehensively judged from the values of other symptoms and markers, but individual renal function Measurement of inulin clearance is recommended for confirmation, and not only the target but also the medical personnel are burdened. As described above, since cystatin C has a narrow measurement range, it is highly likely that it will be determined to be negative in a subject exhibiting impaired renal function. On the other hand, the amount of D-serine in blood is also highly correlated with a decrease in renal function in a wide range of mild to advanced with respect to inulin clearance, and a false-negative cystatin C test can be determined. In addition, the amount of cystatin C, which is greatly affected by physique, also causes false negative / false positive, while D-serine in blood does not show a correlation with body surface area (BSA). It is unlikely to cause false negatives and false positives even for those with a physical constitution.

In the present invention, the renal function test based on the amount of cystatin C in blood may be a test that uses the amount of cystatin C in blood, or a test that uses a numerical value derived from the amount of cystatin C in blood. May be The numerical value derived from the amount of cystatin C in blood is, for example, the estimated glomerular filtration amount, but is not intended to be limited to this. The subject who has undergone the renal function test based on the amount of cystatin C in the blood may have previously undergone the renal function test based on the amount of cystatin C in the blood, or may have it simultaneously. Simultaneously undergoing a renal function test may be tested using the same blood sample collected on the same day or different blood samples, or may be tested using blood samples collected on different days.

Although the amount of D-serine in blood is not intended to be limited to theory, unlike the amount of cystatin C in blood, it is less affected by body size, and in addition to the amount of cystatin C in blood, The advantage is that it has a high correlation with inulin clearance. Therefore, the amount of D-serine in the blood is determined to be a false-positive or false-negative value associated with the amount of cystatin C in the blood measured by a conventional health checkup or the estimated amount of glomerular filtration based on the amount of cystatin C in the blood. Can solve the problem.

In the present invention, false positive refers to a type I error. Specifically, a test based on the amount of cystatin C in the blood and / or the estimated glomerular filtration rate based on the amount of cystatin C in the blood was determined to be positive (that is, renal function declined), while actually suffering from renal function decline. I mean not. False negative refers to type II error. Specifically, a test based on the amount of cystatin C in blood and / or the estimated glomerular filtration rate based on the amount of cystatin C in blood was determined to be negative (that is, renal function is normal), but in reality, renal function was impaired. It means that there is. Although not intending to be limited by theory, in a subject administered with an immunological agent such as a steroid or cyclosporine, the amount of cystatin C in the blood and / or the estimation thread based on the amount of cystatin C in the blood is calculated. Increased likelihood of false positives in tests with spherical filtration rate. False positives and false negatives, as well as true positives and true negatives can be easily understood by referring to the table below.

The false positive determination is performed by determining the renal function decline based on the renal function test based on the amount of cystatin C in the blood, while determining the false positive when the amount of D-serine is lower than the threshold value. . The false negative determination is performed by determining a false negative when the renal function test based on the amount of cystatin C in the blood determines that it is normal, while the amount of D-serine is higher than the threshold value. These threshold values may use a value of 1 regardless of the target element, for example, sex, age, weight, etc., or may be determined according to each classification.

In the present invention, the method for testing false positive or false negative can also be restated as the method for testing true positive or true negative. Specifically, a renal function test based on the amount of cystatin C in the blood determines that renal function is impaired, and when the amount of D-serine exceeds the threshold value, it is determined as true positive. The true negative is determined by determining the true negative when the renal function test based on the amount of cystatin C in the blood determines that it is normal, while the amount of D-serine is higher than the threshold value.

The assay method of the present invention is performed on a blood sample of a subject who has undergone a renal function test based on the amount of cystatin C in blood, and the blood sample is a blood sample used for measuring the amount of cystatin C in blood. The same sample may be used, or the blood sample used to measure the amount of cystatin C in blood may be a sample collected at a different time point.

The method of testing the validity of the present invention does not include a judgment by a doctor because it is performed by comparison with a threshold value. Based on the result of the assay method of the present invention, a doctor can diagnose kidney disease more accurately. Therefore, the assay method of the present invention is a preliminary method of diagnosis or an auxiliary method of diagnosis. The method of the present invention can be carried out by a person other than a doctor, such as a blood analyzer, a health checker, a data processing company, an analysis system, and an analysis program. In still another aspect of the present invention, the method of examining the validity of the present invention may be used to relate to a method of diagnosing renal function or renal disease.

When the false positive and false negative tests of the present invention determine that renal function is deteriorated, early treatment or health guidance is particularly effective in order to prevent further deterioration of renal function. The health guidance mainly includes lifestyle improvement, dietary guidance, blood pressure management, blood sugar level management, lipid management, etc., independently or in combination. Dietary guidance includes salt reduction and protein restriction. As the blood pressure management, the management can be performed so as to be 130/80 mmHg or less. The blood sugar level is controlled to be less than Hba1c 6.9%. In lipid control, LDL-C is controlled to be less than 120 mg / dL. To improve lifestyle habits, smoking cessation and reduction of BMI to less than 25 are recommended.

If a decline in renal function is determined, therapeutic intervention may be given. As therapeutic intervention, blood pressure control, blood sugar level control, anemia control, electrolyte control, uremic toxin control, immune control, lipid control, etc. are performed independently or in combination. Among these, in particular, blood pressure control, blood sugar level control, anemia control, electrolyte control, uremic toxin control, immune control, and lipid control can be treated by medication. As blood pressure management, the blood pressure is controlled so as to be 130/80 mmHg or less, and in some cases, a therapeutic agent for hypertension can be administered. Examples of the antihypertensive drug include diuretics (thiazide diuretics such as trichlormethiazide, benzyl hydrochlorothiazide, hydrochlorothiazide, thiazide-like diuretics such as methicrane, indabamide, tribamide, mefluside, loop diuretics such as furosemide, potassium-retaining drug. Diuretics / aldosterone antagonists such as triamterene, spironolactone, eplerenone, calcium antagonists (dihydropyridines such as nifedipine, amlodipine, efonidipine, cilnidipine, nicardipine, nisoldipine, nitrendipin, nilvadipine, varnidipine, felodipine, benidipine, manidipine, nidipine, manidipine, , Benzothiazepines, diltiazem), angiotensin-converting enzyme inhibitors (captopril) Enalapril, aselapril, delapril, cilazapril, lisinopril, benazepril, imidapril, temocapril, quinapril, trandolapril, belindopril erbumin), angiotensin receptor antagonists (angiotensin II receptor antagonists, such as losartan, candesartan, valsartan, valdesartan, valdesartan, valsarsartan, valsartan , Olmesartan, irbesartan, azilsartan), sympathetic blockers (β-blockers such as atenolol, bisoprolol, betaxolol, metoprolol, aseptol, ceriprolol, propranolol, nadolol, carteolol, pindolol, nipradirol, amosulalol, arotinolol, carvedilol , Labetalol, bevantolol, urapidil, terazosin, brazosin, doxa Shin, bunazosin) or the like can be used. Erythropoietin preparations, iron preparations, HIF-1 inhibitors and the like are used as therapeutic agents for anemia. Calcium receptor agonists (cinacalcet, etelcalcetide, etc.) and phosphorus adsorbents are used as electrolyte modifiers. Activated carbon or the like is used as the uremic toxin adsorbent. Blood glucose levels are controlled to be less than Hbalc 6.9% and hypoglycemic agents are optionally administered. As hypoglycemic agents, SGLT2 inhibitors (ipragliflozin, dapagliflozin, luseogliflozin, tofogliflozin, canagliflozin, empagliflozin, etc.), DPP4 inhibitors (sitagliptin phosphate, vildagliptin, saxagliptin, alogliptin, linagliptin, tenelipliptin, trenlipliptin, threnaliptin , Anagliptin, omalipliptin), sulfonylurea drugs (tolbutamide, acetohexamide, chlorpropamide, glyclopyramide, glibenclamide, gliclazide, glimepiride, etc.), thiazolidine drugs (pioglitazone, etc.), biguanide drugs (metformin, buformin, etc.), α- Glucosidase inhibitors (acarbose, voglibose, miglitol, etc.), glinide drugs (nateglinide, mitiglinide, lepa) Rinido) insulin preparations, NRF2 activator (Bardo Kiso Lung methyl, etc.) and the like. Immunosuppressants (steroids, tacrolimus, anti-CD20 antibody, cyclohexamide, mycophenolate mofetil (MMF), etc.) are used for immune management. In lipid control, LDL-C is controlled to be less than 120 mg / dL, and in some cases, dyslipidemia treatment agents such as statins (rosuvastatin, pitavastatin, atorvastatin, cervastatin, fluvastatin, simvastatin, pravastatin, lovastatin, mevastatin, etc.), Fibrates (clofibrate, bezafibrate, fenofibrate, clinofibrate), nicotinic acid derivatives (tocorelol nicotinate, nicomol, niceritrol), cholesterol transporter inhibitors (ezetimibe), PCSK9 inhibitors (evolocumab, etc.), EPA preparations, etc. Is used. The dosage form of each drug may be a single drug or a combination drug. If renal function declines significantly and the life prognosis is dangerous, renal replacement therapy such as peritoneal dialysis, hemodialysis, continuous hemodiafiltration, blood apheresis (plasma exchange, plasma adsorption, etc.) or renal transplantation is given. .

Another aspect of the present invention may relate to a sample analysis system or program that executes a method for validating a renal function test result based on the amount of cystatin C in blood. FIG. 4 is a block diagram of the sample analysis system of the present invention. The sample analysis system 10 shown in FIG. 4 is configured to be able to carry out the method of the present invention for assaying false negatives and false positives of renal function test results based on the amount of cystatin C in blood. Such a sample analysis system 10 includes a storage unit 11, an input unit 12, an analysis measurement unit 13, a data processing unit 14, and an output unit 15, analyzes a blood sample, and cystatin C in blood. Relevance, ie, true negative, true positive, false negative, or false positive, can be output for the dose-based renal function test results.

More specifically, in the sample analysis system 10 of the present invention,
The storage unit 11 stores the threshold value of the D-serine amount input from the input unit 12,
The storage unit 11 stores the result of the renal function test based on the amount of cystatin C in the blood input from the input unit 12,
The analysis and measurement unit 13 separates and quantifies D-serine in the blood sample,
The data processing unit 14 compares the amount of D-serine with the threshold value of the amount of D-serine stored in the storage unit, and validates the result of the renal function test based on the amount of cystatin C in the blood stored in the storage unit. Is judged,
The output unit 15 can output the validity of the result of the renal function test based on the amount of cystatin C in blood.

In a further preferred embodiment, in the sample analysis system of the present invention, the storage unit 11 replaces the step of storing the result of the renal function test based on the amount of cystatin C in the blood input from the input unit 12, instead of the analysis measurement unit 13. May include the step of determining the amount of Cystatin C in the blood sample. In this case, the data processing unit 14 may further include a step of determining the result of the renal function test based on the amount of cystatin C in the blood sample, and storing the determined result in the storage unit. In this case, the storage unit 11 stores in advance a threshold value for the amount of cystatin C in blood input from the input unit 12, and the data processing unit 14 stores the amount of cystatin C in blood and the stored amount of cystatin C in blood. The result of the renal function test is determined by comparison with the threshold value of

More specifically, in the sample analysis system 10 of the present invention in one aspect,
The storage unit 11 stores the threshold value of the amount of cystatin C in the blood input from the input unit 12,
The storage unit 11 stores the threshold value of the D-serine amount input from the input unit 12,
The analysis and measurement unit 13 measures the amount of cystatin C in the blood sample,
The data processing unit 14 compares the threshold value of the amount of cystatin C in the blood stored in the storage unit with the amount of cystatin C in the blood sample, and determines and analyzes the result of the renal function test based on the amount of cystatin C in the blood. The measurement unit 13 separates and quantifies D-serine in the blood sample,
The data processing unit 14 compares the amount of D-serine in the blood with the threshold value of the amount of D-serine stored in the storage unit, and determines the validity of the result of the renal function test based on the amount of cystatin C in the blood. ,
The output unit 15 can output the validity of the result of the renal function test based on the amount of cystatin C in blood.

As the amount of cystatin C in blood, a numerical value derived from the amount of cystatin C in blood (for example, estimated glomerular filtration rate) can also be used. As an example, when the numerical value derived from the amount of cystatin C in blood is used, the storage unit 11 stores the other factors such as the age and sex of the target input from the input unit 12, and further the amount of cystatin C in blood. The formula or graph for calculating the numerical value derived from is stored, and the data processing unit 14 stores the measured amount of cystatin C in the blood and other factors such as the age and sex of the target stored in the storage unit 11. The step of calculating a numerical value from an equation or a graph for calculating a numerical value derived from the amount of cystatin C in blood may be included. As an example of the threshold value of the estimated glomerular filtration rate, 60 mL / min / 1.73 m ² can be used.

More specifically, when using the estimated glomerular filtration rate, in the sample analysis system 10 of the present invention,
The storage unit 11 stores a calculation formula for an estimated glomerular filtration amount based on the amount of cystatin C in blood input from the input unit 12,
The storage unit 11 stores the age and sex of the subject input from the input unit 12,
The storage unit 11 stores a threshold value of a glomerular filtration amount based on the amount of cystatin C in blood input from the input unit 12,
The storage unit 11 stores the threshold value of the D-serine amount input from the input unit 12,
The analysis and measurement unit 13 measures the amount of cystatin C in the blood sample,
The data processing unit 14 calculates the estimated glomerular filtration amount from the amount of cystatin C in the blood, the age and sex of the subject stored in the storage unit, and the calculation formula of the estimated glomerular filtration amount,
The data processing unit 14 compares the threshold value of the estimated glomerular filtration amount stored in the storage unit with the calculated estimated glomerular filtration amount, and determines the result of the renal function test based on the amount of cystatin C in blood,
The analysis and measurement unit 13 separates and quantifies D-serine in the blood sample,
The data processing unit 14 compares the amount of D-serine in the blood with the threshold value of the amount of D-serine stored in the storage unit, and determines the validity of the result of the renal function test based on the amount of cystatin C in the blood. ,
The output unit 15 can output the validity of the result of the renal function test based on the amount of cystatin C in blood.

Regarding the validity of the result of the renal function test in the data processing unit 14, the validity of the result of the renal function test based on the amount of cystatin C in the blood is determined by comparing the amount of D-serine with the threshold value. Specifically, a renal function test based on the amount of cystatin C in the blood was determined to be renal function decline, but when the amount of D-serine was lower than the threshold value, it was determined as a false positive, and the amount of D-serine was determined. Is higher than the threshold, it can be determined to be a true positive. On the other hand, a renal function test based on the amount of cystatin C in the blood determined to be normal, and on the other hand, when the amount of D-serine was higher than the threshold value, it was determined as a false negative, and the amount of D-serine was higher than the threshold value. If low, it can be determined to be true negative.

The storage unit 11 has a memory device such as a RAM, a ROM, a flash memory, a fixed disk device such as a hard disk drive, or a portable storage device such as a flexible disk or an optical disk. The storage unit stores data measured by the analysis measurement unit, data and instructions input from the input unit, results of arithmetic processing performed by the data processing unit, computer programs used for various processes of the information processing device, a database, and the like. Remember. The computer program may be installed via a computer-readable recording medium such as a CD-ROM or a DVD-ROM, or the Internet. The computer program is installed in the storage unit using a known setup program or the like. The storage unit can store the threshold value of the amount of D-serine and the result of the renal function test based on the amount of cystatin C in the blood, which are input in advance from the input unit 12. Furthermore, the threshold value of the amount of cystatin C in the blood for the renal function test can be stored. Further, when the estimated glomerular filtration rate is used instead of the cystatin C amount in blood, a threshold value of the estimated glomerular filtration rate may be stored, and further, the estimated glomerular filtration rate based on the cystatin C amount in blood. The formula for calculating the amount can be stored, and the age and sex of the subject can be stored. In addition, the result measured by the analysis measurement unit 13 and the result of the processing performed by the data processing unit 14 are also stored.

The input unit 12 is an interface and the like, and also includes operation units such as a keyboard and a mouse. Thereby, the input unit can input the data measured by the analysis measurement unit 13, the instruction of the arithmetic processing performed by the data processing unit 14, and the like. Further, the input unit 12 may include an interface unit capable of inputting measured data or the like via a network or a storage medium, in addition to the operation unit, for example, when the analysis measurement unit 13 is external.

The analysis / measurement unit 13 performs the measurement process of D-serine in the blood sample. Therefore, the analysis and measurement unit 13 has a configuration that enables separation and measurement of D-form and L-form of amino acids. The amino acids may be analyzed one by one, but some or all types of amino acids may be analyzed together. The analysis and measurement unit 13 is not intended to be limited to the following, but is, for example, a chiral chromatography system including a sample introduction unit, an optical resolution column, and a detection unit, and preferably a high performance liquid chromatography system. May be. From the viewpoint of detecting only a specific amino acid amount, it may be carried out by an enzymatic method or an immunological method. The analysis measurement unit 13 may be configured separately from the sample analysis system, and the measured data and the like may be input via the input unit 12 using a network or a storage medium. Furthermore, in another aspect, the analysis measurement unit 13 can also measure the amount of cystatin C in blood.

The data processing unit 14 executes various arithmetic processes on the data measured by the analysis and measurement unit 13 and stored in the storage unit 11 according to the program stored in the storage unit. The arithmetic processing is performed by the processor or CPU included in the data processing unit. This processor or CPU includes a functional module that controls the analysis measurement unit 13, the input unit 12, the storage unit 11, and the output unit 15, and can perform various controls. Each of these units may be composed of an independent integrated circuit, microprocessor, firmware, or the like. The data processing unit 14 compares the amount of D-serine with the threshold value of the amount of D-serine stored in the storage unit, and validates the result of the renal function test based on the amount of cystatin C in the blood stored in the storage unit. To judge. In another aspect, the data processing unit 14 calculates the estimated glomerular filtration amount from the amount of cystatin C in the blood, the age and sex of the subject stored in the storage unit, and the calculation formula of the estimated glomerular filtration amount. be able to. In this case, the data processing unit 14 further compares the threshold value of the estimated glomerular filtration amount stored in the storage unit with the calculated estimated glomerular filtration amount, and performs the renal function test based on the amount of cystatin C in the blood. It is also possible to judge the result.

The output unit 15 is configured to output the validity of the result of the renal function test based on the amount of cystatin C in the blood determined by the data processing unit, that is, true negative, true positive, false negative, or false positive. . Further, the output unit 15 outputs the amount of D-serine measured by the analysis measurement unit 13, the amount of cystatin C in blood, or the estimated glomerular filtration amount calculated by the data processing unit 14 together with the above-mentioned validity. You may. The output unit 15 may be a display device such as a liquid crystal display that directly displays the result of the arithmetic processing, an output unit such as a printer, or an interface unit for outputting to an external storage device or via a network. It may be.

FIG. 5 is a flowchart showing an example of an operation for determining the glomerular filtration rate by the program of the present invention. Specifically, the program of the present invention is a program that causes an information processing apparatus including an input unit, an output unit, a data processing unit, and a storage unit to determine the validity of the result of a renal function test based on the amount of cystatin C in blood. is there. The program of the present invention is as follows:
The threshold value of the amount of D-serine input from the input unit is stored in the storage unit,
The result of the renal function test based on the amount of cystatin C in the blood input from the input unit is stored in the storage unit,
The amount of D-serine in the blood sample input from the input unit is stored,
The amount of D-serine stored in the storage unit and the threshold value of the amount of D-serine are read out, compared in the data processing unit, and the result of the comparison is stored in the storage unit as to whether the amount exceeds or falls below the threshold value.
The result of the renal function test based on the amount of cystatin C in the blood stored in the memory unit and the result of the comparison are read, the validity of the result of the renal function test is determined, and the result is stored in the memory unit.
The information processing apparatus includes a command for causing the information processing apparatus to output the stored validity to the output unit. The program of the present invention may be stored in a storage medium, or may be provided via an electric communication line such as the Internet or LAN.

-The validity of the results of the renal function test is determined based on the results of the renal function test and the results of comparison. Specifically, a renal function test based on the amount of cystatin C in the blood was determined to be renal function decline, but when the amount of D-serine was lower than the threshold value, it was determined as a false positive, and the amount of D-serine was determined. Is higher than the threshold, it can be determined to be a true positive. On the other hand, a renal function test based on the amount of cystatin C in the blood determined to be normal, and on the other hand, when the amount of D-serine was higher than the threshold value, it was determined as a false negative, and the amount of D-serine was higher than the threshold value. If low, it can be determined to be true negative.

The program of the present invention allows the data processing unit 14 to input the amount of cystatin C in blood from the input unit 12 instead of inputting the result of the renal function test based on the amount of cystatin C in blood from the input unit 12. The instruction may be compared with the threshold value of the amount of cystatin C in the blood stored in the storage unit 11 to determine the result of the renal function test.

More specifically, the program of the present invention replaces the command for storing the result of the renal function test based on the amount of cystatin C in the blood input from the input unit 12 in the storage unit 11 with the following:
The threshold value of the amount of cystatin C in the blood input from the input unit 12 is stored in the storage unit 11,
The amount of cystatin C in the blood input from the input unit 12 is stored in the storage unit 11,
The amount of cystatin C in the blood stored in the storage unit 11 and the threshold value of the amount of cystatin C in the blood are read out and compared by the data processing unit 14, and the result of the renal function test is determined depending on whether the amount exceeds or falls below the threshold value. Then, the program may include a command to store the result of the renal function test in the storage unit 11.

When the information processing apparatus includes the analysis and measurement unit 13, instead of inputting the result of the renal function test based on the amount of cystatin C in blood from the input unit 12, the amount of D-serine in the blood sample is input to the analysis and measurement unit 13. May be separated and quantified, and the data processing unit 14 may include a command for determining the result of the renal function test by comparing with the threshold value of the amount of cystatin C in the blood stored in the storage unit 11.

More specifically, the program of the present invention replaces the command for storing the result of the renal function test based on the amount of cystatin C in the blood input from the input unit 12 in the storage unit 11 with the following:
The threshold value of the amount of cystatin C in the blood input from the input unit 12 is stored in the storage unit 11,
The analysis and measurement unit 13 is operated to measure the amount of cystatin C in blood, and stored in the storage unit 11,
The amount of cystatin C in the blood and the threshold value of the amount of cystatin C in the blood stored in the storage unit 11 are read out and compared in the data processing unit 14 to determine the result of the renal function test and determine the renal function test. The program may include a command to store the result in the storage unit 11.

A program using an estimated glomerular filtration rate calculated from the amount of cystatin C in blood may be used instead of the amount of cystatin C in blood. In this case, instead of a command to store the estimated glomerular filtration rate input from the input unit in the storage unit,
The age and sex of the subject input from the input unit 12 are stored in the storage unit 11,
The storage unit 11 stores the calculation formula of the estimated glomerular filtration amount based on the amount of cystatin C in the blood, which is input from the input unit 12,
The analysis and measurement unit 13 is caused to measure the amount of cystatin C in the blood sample and stored in the storage unit 11,
Even if the data processing unit includes a command for substituting the age, sex, and the amount of cystatin C in blood stored in the storage unit into the calculation formula to calculate the estimated glomerular filtration amount and store it in the storage unit 11. Good.

All references mentioned in this specification are incorporated herein by reference in their entirety.

The embodiments of the present invention described below are for illustrative purposes only and do not limit the technical scope of the present invention. The technical scope of the present invention is limited only by the description of the claims. Modifications of the present invention, for example, addition, deletion, and replacement of the constituent features of the present invention, can be made on the condition that the gist of the present invention is not deviated.

Subject group Consists of chronic kidney disease (CKD) patients admitted to the Department of Nephrology (Department of Nephrology, Osaka University Hospital) for the purpose of diagnosis and / or treatment from 2016 to 2017 From the cohort, 11 patients were used in the retrospective study. Separately, we recruited 15 healthy volunteers over the age of 20 at the National Institute of Medical Science, Health and Nutrition. The study protocol was approved by the ethics committee at each institution and documented informed consent was obtained from all subjects.

Information on healthy people and patients with chronic kidney disease is as follows:

Method for Measuring Inulin Renal Clearance The inulin clearance (Cin) of a subject was calculated from the inulin concentration in plasma and urine and the urine volume according to the standard method described in Clin Exp Nephrol 13,50-54 (2009). Briefly, under fasting, postponement of medication, and water-loaded environment, 1% inulin (Inulead Note: Fuji Yakuhin Co., Ltd.) was administered to a blood and urine sample at three different time points during a continuous intravenous infusion of 2 hours. It was collected in. The test subject drank 500 mL of water orally 30 minutes before the infusion. To maintain the water load, 60 mL of water was drunk 40, 60, 90 minutes after the start of the inulin drip. The initial rate of infusion was 300 mL / h for the first 30 minutes, followed by 100 mL / h for 90 minutes. Blood samples were taken at 45, 75, and 105 minutes after the start of inulin infusion. The subject urinated so as to completely empty the bladder 30 minutes after the start of infusion. Urine samples were then taken between 30 and 60 minutes, between 60 and 90 minutes, and between 90 and 120 minutes. Inulin was measured using the enzymatic method. The average of three Cin values was used as Cin (Cin-ST) by the standard method.

Sample Preparation of D-Amino Acids in Blood Sample Preparation Sample preparation from human plasma was performed as follows:
20 volumes of methanol were added to plasma and mixed thoroughly. After centrifugation, 10 μL of the supernatant obtained from methanol homogenate was transferred to a brown tube and dried under reduced pressure. For the residue, 20 μL of 200 mM sodium borate buffer (pH 8.0) and 5 μL of fluorescent labeling reagent (40 mM 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD in anhydrous MeCN). -F)) was added and then heated at 60 0 C for 2 minutes. The reaction was stopped by adding 75 μl of 0.1% TFA aqueous solution (v / v), and 2 μL of the reaction mixture was subjected to two-dimensional HPLC.

Quantification of amino acid optical isomers by two-dimensional HPLC Amino acid optical isomers were quantified using the following two-dimensional HPLC system. A mobile phase (5-35% MeCN, 0-20% THF, and 0.05% TFA) of an NBD derivative of an amino acid was used as a mobile phase using a reverse phase column (KSAA RP, 1.0 mm id x 400 mm; Shiseido Co., Ltd.). Was separated and eluted. The column temperature was set to 45 ° C. and the mobile phase flow rate was set to 25 μL / min. The separated amino acid fraction was collected using a multi-loop valve and continuously optically resolved by a chiral column (KSAACSP-001S, 1.5 mm id x 250 mm; Shiseido). As a mobile phase, a MeOH-MeCN mixed solution containing citric acid (0 to 10 mM) or formic acid (0 to 4%) was used according to the retention of amino acids. NBD-amino acid was detected by fluorescence at 530 nm using excitation light of 470 nm. The retention time of NBD-amino acid was identified by a standard of optical amino acid isomers and quantified by a calibration curve.

Correlation analysis with GFR (inulin clearance) (1) Body surface area correction GFR (inulin clearance) with body surface area correction, blood D-serine amount (A), cystatin C amount (of 26 subjects) B) and were plotted on a scatter plot, and the correlation coefficient r and p value were calculated. The results are shown in Fig. 1. It was shown that the amount of D-serine in blood was equivalent to the amount of cystatin C in blood for GFR (inulin clearance). In the data analysis of GFR (inulin clearance) 100 or less (n = 21), the correlation between the amount of D-serine in blood and the body surface area-corrected GFR (inulin clearance) and the amount of cystatin C in blood were compared. The correlation with the body surface area-corrected GFR (inulin clearance) was analyzed. Below 100 GFR, the correlation coefficient r value and p value between the D-serine amount in blood and GFR (inulin clearance) are -0.713 and 0.00042, respectively, and the amount of cystatin C in blood and GFR (inulin clearance) are respectively. The correlation coefficients r and p with the clearance) were -0.656 and 0.0013, respectively. It has been shown that the correlation between the amount of D-serine in blood and GFR (inulin clearance) is higher than that of GFR100 than that between the amount of cystatin C in blood and GFR (inulin clearance).

(2) Body surface area uncorrected For 26 subjects, the GFR (inulin clearance) without body surface area correction, the amount of D-serine in blood (A), and the amount of cystatin C (B) were plotted in a scatter diagram. Then, the correlation coefficient r and p value were calculated. The results are shown in Figure 2. It was shown that the amount of D-serine in blood was more correlated with the amount of GFR (inulin clearance) without body surface area correction than the amount of cystatin C in blood.

Correlation with body surface area (BSA) For the data of healthy subjects (GFR> 70), the body surface area (BSA) and the measured amounts of D-serine and cystatin C in blood are shown in a scatter diagram, and the correlation coefficient r Values and p-values were calculated. The results are shown in Fig. 3. The amount of cystatin C correlated with the body surface area, whereas the amount of D-serine in blood did not correlate with the body surface area.

Claims (13)

1. A method for testing the validity of a renal function test result based on the amount of cystatin C in blood, comprising:
   Measuring the amount of D-serine in the blood of a subject who has undergone a renal function test based on the amount of cystatin C in the blood,
   The method, comprising the steps of comparing the amount of D-serine with a predetermined threshold value, and determining the validity of the results of the renal function test based on the amount of cystatin C in blood.
2. The method according to claim 1, wherein the method of testing the adequacy of the renal function test result determines false positive and / or false negative renal function test result based on the amount of cystatin C in the blood.
3. The false positive is determined in the determining step when the renal function test based on the amount of cystatin C in the blood determines that renal function is impaired, while the amount of D-serine is lower than the threshold value. The method described.
4. 3. The false determination according to claim 2, wherein in the determining step, when a renal function test based on the amount of cystatin C in the blood determines that the D-serine amount is higher than the threshold, the determination is normal. Method.
5. The method according to any one of claims 1 to 4, wherein the amount of D-serine and the amount of cystatin C in blood are measured in the same sample.
6. The method according to any one of claims 1 to 5, wherein the subject is a subject administered with a drug that acts on the immune system.
7. A sample analysis system comprising a storage section, an input section, an analytical measurement section, a data processing section, and an output section for testing the validity of a renal function test result based on the amount of cystatin C.
   The storage unit stores the threshold value of the amount of D-serine input from the input unit,
   The storage unit stores the result of the renal function test based on the amount of cystatin C in the blood input from the input unit,
   The analysis and measurement unit separates and quantifies D-serine in the blood sample,
   The data processing unit compares the amount of D-serine with the threshold value of the amount of D-serine stored in the storage unit, and validates the result of the renal function test based on the amount of cystatin C in the blood stored in the storage unit. Judge,
   The sample analysis system, wherein the output unit outputs the validity of the result of the renal function test based on the amount of cystatin C in blood.
8. The sample analysis system according to claim 7, wherein the validity of the renal function test result is determined as a false positive and / or a false negative of the renal function test result based on the amount of cystatin C in the blood.
9. 9. The determination according to claim 8, wherein a renal function test based on the amount of cystatin C in the blood determines that renal function is impaired, while the amount of D-serine is lower than the threshold value, the determination is false positive. Sample analysis system.
10. The sample according to claim 8, wherein the determination is determined to be normal by a renal function test based on the amount of cystatin C in blood, while a false negative is determined when the amount of D-serine is higher than the threshold value. Analysis system.
11. The sample analysis system according to any one of claims 7 to 10, wherein the amount of D-serine and the amount of cystatin C in blood are measured in the same sample.
12. A program that causes an information processing apparatus including an input unit, an output unit, a data processing unit, and a storage unit to determine the validity of a result of a renal function test based on the amount of cystatin C in blood, which is as follows:
    The threshold value of the amount of D-serine input from the input unit is stored in the storage unit,
    The result of the renal function test based on the amount of cystatin C in the blood input from the input unit is stored in the storage unit,
    The amount of D-serine in the blood sample input from the input unit is stored,
    The amount of D-serine stored in the storage unit and the threshold value of the amount of D-serine are read out, compared in the data processing unit, and the result of the comparison is stored in the storage unit as to whether the amount exceeds or falls below the threshold value.
    The result of the renal function test based on the amount of cystatin C in the blood stored in the memory unit and the result of the comparison are read, the validity of the result of the renal function test is determined, and the result is stored in the memory unit.
    The program, which includes a command for causing the information processing apparatus to cause the output unit to output the stored validity.
13. A program that causes an information processing apparatus including an input unit, an output unit, a data processing unit, and a storage unit to determine the validity of a result of a renal function test based on the amount of cystatin C in blood, which is as follows:
    The threshold value of the amount of cystatin C in the blood input from the input unit is stored in the storage unit,
    Store the amount of Cystatin C in the blood sample input from the input unit,
    The threshold value of the amount of D-serine input from the input unit is stored in the storage unit,
    The amount of D-serine in the blood sample input from the input unit is stored,
    The amount of cystatin C in the blood stored in the storage unit and the threshold value of the amount of cystatin C in the blood are read out, compared in the data processing unit, and the renal function test result based on the amount of cystatin C is stored in the storage unit,
    The amount of D-serine stored in the storage unit and the threshold value of the amount of D-serine are read out, compared in the data processing unit, and the result of the comparison is stored in the storage unit,
    The result of the renal function test based on the amount of cystatin C in the blood stored in the memory unit and the result of the comparison are read, the validity of the result of the renal function test is determined, and the result is stored in the memory unit.
    The program, which includes a command for causing the information processing apparatus to cause the output unit to output the stored validity.

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