Determination Of Hemoglobin A1c Research Articles

Commutability and Uncertainty of Blood Hemoglobin A1c Testing Materials.

Hemoglobin A1C (HbA1C) is used to evaluate glycemic control over a three-month period. Blood matrix-based HbA1C materials are needed for quality control and evaluation of HbA1C measurements. This study investigated the commutability of blood materials (BMs) and aimed to upgrade BMs for HbA1C testing for use as proficiency test (PT) material. We measured BMs from a DM blood donor (n = 1), an in vitro glycation procedure (n = 3), and from commercial sources (n = 2) for HbA1C in parallel with fresh unprocessed BMs (n = 3) and clinical blood samples (n = 25). Two NGSP-certified methods, including a turbidimetric and an enzymatic immunoassay, were used for HbA1C determinations. Commutability as investigated according to CLSI EP14-Ed4 guidelines. The commutable BMs exhibited a mean paired difference of 0% to 9% when compared to reference methods, whereas the non-commutable BMs represented a mean paired difference of 3% to 11%. Fresh, unprocessed BMs with a low HbA1C of 6.0% were more commutable than BMs with a high HbA1C. The values of HbA1C in BMs (mean and uncertainty following ISO Guide 35 for RM production) were applied to upgrade the PT material to be used as a reference material. The relative uncertainty of BM-Ndm-1 and BM-Gcb-3 were 1 and 0.4%, respectively. The commutability of hemoglobin in BMs is dependent on the preparation process. Blood materials with a high HbA1C content are usually less commutable versus materials with low HbA1C content when prepared by the same process. Our study showed BMs can be successfully used as quality control or PT materials.

HbA1c comparison and diagnostic efficacy analysis of multi center different glycosylated hemoglobin detection systems

Objective: Compare and analyze the results of the domestic Lanyi AH600 glycated hemoglobin analyzer and other different detection systems to understand the comparability of the detection results of different detectors, and establish the best cut point of Lanyi AH600 determination of haemoglobin A1c (HbA1c) in the diagnosis of diabetes. Methods: Multi center cohort study was adopted. The clinical laboratory departments of 18 medical institutions independently collected test samples from their respective hospitals from March to April 2022, and independently completed comparative analysis of the evaluated instrument (Lanyi AH600) and the reference instrument HbA1c. The reference instruments include four different brands of glycosylated hemoglobin meters, including Arkray, Bio-Rad, DOSOH, and Huizhong. Scatter plot was used to calculate the correlation between the results of different detection systems, and the regression equation was calculated. The consistency analysis between the results of different detection systems was evaluated by Bland Altman method. Consistency judgment principles: (1) When the 95% limits of agreement (95% LoA) of the measurement difference was within 0.4% HbA1c and the measurement score was≥80 points, the comparison consistency was good; (2) When the measurement difference of 95% LoA exceeded 0.4% HbA1c, and the measurement score was≥80 points, the comparison consistency was relatively good; (3) The measurement score was less than 80 points, the comparison consistency was poor. The difference between the results of different detection systems was tested by paired sample T test or Wilcoxon paired sign rank sum test; The best cut-off point of diabetes was analyzed by receiver operating characteristic curve (ROC). Results: The correlation coefficient R2 of results between Lanyi AH600 and the reference instrument in 16 hospitals is≥0.99; The Bland Altman consistency analysis showed that the difference of 95% LoA in Nanjing Maternity and Child Health Care Hospital in Jiangsu Province (reference instrument: Arkray HA8180) was -0.486%-0.325%, and the measurement score was 94.6 points (473/500); The difference of 95% LoA in the Tibetan Traditional Medical Hospital of TAR (reference instrument: Bio-Rad Variant II) was -0.727%-0.612%, and the measurement score was 89.8 points; The difference of 95% LoA in the People's Hospital of Chongqing Liang Jiang New Area (reference instrument: Huizhong MQ-2000PT) was -0.231%-0.461%, and the measurement score was 96.6 points; The difference of 95% LoA in the Taihe Hospital of traditional Chinese Medicine in Anhui Province (reference instrument: Huizhong MQ-2000PT) was -0.469%-0.479%, and the measurement score was 91.9 points. The other 14 hospitals, Lanyi AH600, were compared with 4 reference instrument brands, the difference of 95% LoA was less than 0.4% HbA1c, and the scores were all greater than 95 points. The results of paired sample T test or Wilcoxon paired sign rank sum test showed that there was no statistically significant difference between Lanyi AH600 and the reference instrument Arkray HA8180 (Z=1.665,P=0.096), with no statistical difference. The mean difference between the measured values of the two instruments was 0.004%. The comparison data of Lanyi AH600 and the reference instrument of all other institutions had significant differences (all P<0.001), however, it was necessary to consider whether it was within the clinical acceptable range in combination with the results of the Bland-Altman consistency analysis. The ROC curve of HbA1c detected by Lanyi AH600 in 985 patients with diabetes and 3 423 patients with non-diabetes was analyzed, the area under curve (AUC) was 0.877, the standard error was 0.007, and the 95% confidence interval 95%CI was (0.864, 0.891), which was statistically significant (P<0.001). The maximum value of Youden index was 0.634, and the corresponding HbA1c cut point was 6.235%. The sensitivity and specificity of diabetes diagnosis were 76.2% and 87.2%, respectively. Conclusion: Among the hospitals and instruments currently included in this study, among these four hospitals included Nanjing Maternity and Child Health Care Hospital in Jiangsu Province (reference instrument: Arkray HA8180), Tibetan Traditional Medical Hospital of TAR (reference instrument: Bio-Rad Variant Ⅱ), the People's Hospital of Chongqing Liang Jiang New Area (reference instrument: Huizhong MQ-2000PT), and the Taihe Hospital of traditional Chinese Medicine in Anhui Province (reference instrument: Huizhong MQ-2000PT), the comparison between Lanyi AH600 and the reference instruments showed relatively good consistency, while the other 14 hospitals involved four different brands of reference instruments: Arkray, Bio-Rad, DOSOH, and Huizhong, Lanyi AH600 had good consistency with its comparison. The best cut point of the domestic Lanyi AH600 for detecting HbA1c in the diagnosis of diabetes is 6.235%.

Determination of hemoglobin A1c (HbA1c), alkaline phosphatase (ALP), aspartate aminotransferase (AST), superoxide dismutase (SOD) values and lipid profiles in rats fed with corn syrup and trans oil added diets

Determination of hemoglobin A1c (HbA1c), alkaline phosphatase (ALP), aspartate aminotransferase (AST), superoxide dismutase (SOD) values and lipid profiles in rats fed with corn syrup and trans oil added diets

Usefulness of Automated Hb-HPLC Analyzer Based on Reverse-Phase Cation-Exchange Chromatography for Hemoglobin A1C Determination in the Setting with High Prevalence of Hemoglobin E Disorder.

Usefulness of Automated Hb-HPLC Analyzer Based on Reverse-Phase Cation-Exchange Chromatography for Hemoglobin A1C Determination in the Setting with High Prevalence of Hemoglobin E Disorder.

A Novel Label-Free Immunosensor Based on Electrochemically Reduced Graphene Oxide for Determination of Hemoglobin A1c

In this work, a novel immunosensor has been developed using an electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE) for sensitive and label-free detection of glycated hemoglobin (HbA1c) used as the gold standard marker for glycemic control. The prepared immunosensor, using ferrocyanide/ferricyanide as the mediator, ensures an uncomplicated and economic method for the detection of HbA1c. The proposed immunosensor can directly record changes in the electrochemical signals when the immunoreaction occurs on the sensor surface. The specific antibody-antigen immunoreaction resulted in a reduction in the amperometric response of the mediator that diffused at the electrode surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques were utilized to investigate the electrochemical characteristics of the immunosensor. Calibration curve was plotted via differential pulse voltammetry (DPV) technique and a linear relationship was obtained between the DPV response and HbA1c concentrations from 1 to 25%. Under the optimized condition, the GCE/ERGO/HbA1cAb immunosensor supplied high selectivity and sensitivity for HbA1c detection in real serum samples.

Prevalence of diabetes and frequency of glycated haemoglobin monitoring in Extremadura (Spain) during 2012, 2013 and 2014: An observational study

AimsTo analyze the prevalence of diabetes and the frequency of haemoglobin A1C (HbA1C) monitoring in the population with diabetes in Extremadura (Spain). MethodsObservational, longitudinal retrospective study in the population attended in the Extremadura Health System in 2012–2014. A total of 403,644 glycated haemoglobin determinations in 189,466 subjects (52.4% female) were studied. All patients with a prescription of antidiabetic drugs and those who, despite not having treatment, had any determination of HbA1C ≥6.5% were considered as people with diabetes. All patients without treatment but with HbA1C ≥5.7% and <6.5% were considered prediabetes patients. ResultsThe prevalence rate of diabetes was 8.3% and the frequency of HbA1C monitoring was 0.9/patient/year in the diabetic population. 48.2% of the patients with monitoring of HbA1C had diabetes, 21.2% had prediabetes, and 30.6% did not meet the criteria for diabetes or prediabetes. 12.7% of people with diabetes did not have determinations of HbA1C and only 11.8% have had ≥6 determinations in the period analyzed. ConclusionsThe frequency of HbA1C monitoring in the diabetic population is lower than that usually recommended. Moreover, there is an inadequate use of HbA1C determinations, since one out of every 3 patients does not meet the criteria for diabetes or prediabetes.

Standardization of glycated hemoglobin A1c determination and its accuracy

Standardization of glycated hemoglobin A1c determination and its accuracy

Hemoglobin-A-1c-szint-mérés: analitikai vonatkozások és ezek jelentősége a klinikai döntéshozatalban

Appropriate care and monitoring of the condition of patients with diabetes is indispensable from the regular measurement of hemoglobin A1c levels. Under well defined criteria hemoglobin A1c levels may also support the diagnosis of diabetes. This review provides a short description of the major principles of methods used for hemoglobin A1c determination and it reviews conditions interfering with the results. It also presents cut-off values for therapeutic decision making. As the results of world-wide efforts for standardization of hemoglobin A1c values obtained with different tests in different laboratories, the hemoglobin A1c results are comparable and can be used for clinical decisions. However, hemoglobin A1c should be considered with a particular caution in patients with hemoglobinopathies and in those with conditions affecting the average life-time of red cells.

A colloidal gold-based lateral flow immunoassay for direct determination of haemoglobin A1c in whole blood

We developed an immunosensor that operates based on the lateral flow principle designed to detect haemoglobin A1c (HbA1c), a biomarker for type 2 diabetes mellitus in human blood samples.

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update Emma English,1 Elise T Milosevich,1 W Garry John2 1School of Medicine, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom; 2Department of Clinical Biochemistry, Norfolk and Norwich University Hospital, Norwich, United Kingdom Abstract: It is fascinating to consider the analytical improvements that have occurred since glycated hemoglobin was first used in routine clinical laboratories for diabetes monitoring around 1977; at that time methods displayed poor precision, there were no calibrators or material with assayed values for quality control purposes. This review outlines the major improvements in hemoglobin A1c (HbA1c) measurement that have occurred since its introduction, and reflects on the increased importance of this hemoglobin fraction in the monitoring of glycemic control. The use of HbA1c as a diagnostic tool is discussed in addition to its use in monitoring the patient with diabetes; the biochemistry of HbA1c formation is described, and how these changes to the hemoglobin molecule have been used to develop methods to measure this fraction. Standardization of HbA1c is described in detail; the development of the IFCC Reference Measurement Procedure for HbA1c has enabled global standardization to be achieved which has allowed global targets to be set for glycemic control and diagnosis. The importance of factors that may interfere in the measurement of HbA1c are highlighted. Keywords: glycated hemoglobin, HbA1c, IFCC

Glycated hemoglobin a1c as a modern biochemical marker of glucose regulation

GLYCATED HEMOGLOBIN STRUCTURE AND SYNTHESIS OF MOLECULE: Glycated hemoglobin A1c, the major fraction of glycated hemoglobin, is formed by irreversible nonenzymatic glycation. Its concentration depends only on the life span of red blood cells and blood glucose levels. CLINICAL SIGNIFICANCE OF GLYCATED HEMOGLOBIN A1c: It is the key parameter for monitoring the regulation of diabetes and for assessing the risk of microvascular complications. It is a diagnostic criterion for diabetes as well. Its concentration reflects the average value of blood glucose over the last two to three months. The estimated average glucose, a new parameter which facilitates the patient's self-monitoring of diabetes, can be calculated from its value. METHODS FOR DETERMINING GLYCATED HEMOGLOBIN A1c AND THEIR STANDARDIZATION: Immunoassay and ion-exchange chromatography are commonly used methods for the glycated hemoglobin determination in routine laboratory practice. The advantage of immunoassay is that there is no need for the sample pre-treatment in order to eliminate unstable glycated hemoglobin A1c intermediary forms, and the possibility of false positive results is lower. The current program of standardization requires traceability to the International Federation of Clinical Chemistry and Laboratory Medicine reference method. REPORTING AND INTERPRETATION OF RESULTS OF GLYCATED HEMOGLOBIN A1c DETERMINATION: Glycated Hemoglobin A1c can be reported as % or as mmol/mol. In our country, it is recommended to use the International Federation of Clinical Chemistry and Laboratory Medicine units (mmol/mol). When interpreting the results, the potential causes of falsely high or low values must always be taken into consideration. Periodic determinations of glycated hemoglobin A1c are recommended for monitoring of diabetes regulation. Additionally, the determination is recommended for the diagnosis of diabetes. The target value for the prevention of microvascular complications is < 7% and the diagnostic criterion for diabetes is 6.5%.

Hemoglobin A1C determination by point-of-care testing: Its correlation to standard method

The hemoglobin A1C (HbA1C) is the useful test for following up of glycemic control of the diabetic patient. Due to the present advance in point-of-care testing (POCT) technology, the new POCT for determination of HbA1C is available. Here, the author performs a laboratory comparative study between the new POCT tool (DCA) and classical tool (COBAS) for analysis of HbA1C level. This study is the second confirmation study in Thailand performed in the new setting adding to the previous author's report. The results show that there is a good correlation between two techniques and the error of the POCT tool is within acceptable limit.

Point of care testing for pediatric following up of hemoglobin A1C: Concern on product's property

Point of care testing (POCT) is a new concept in laboratory medicine. The POCT tool helps perform the laboratory test at site giving fast result and requires only small amount of sample. It is presently and increasingly used in pediatrics. In pediatric diabetology, the use of POCT for following up of hemoglobin A1C is a new concept. At present, there are several POCT tools for this purpose. In this specific article, the author compares on important aspects (turnaround time and required amount of specimen) of 5 available POCT tools for measurement of hemoglobin A1C level. The test that is the fastest and requires the least amount of blood sample, which means the least harm to the pediatric patient is the most preferable. Here, it can be seen that there is no ideal POCT that has both properties. However, if it is standardized to compare the amount of required blood sample, the special concern in the pediatric patients, the product from multiplication shows that Siemen DCA 2000+ and Siemen DCA Vantage are the two most preferable POCT tools for hemoglobin A1C determination in pediatric diabetes mellitus management.

FET immunosensor for hemoglobin A1c using a gold nanofilm grown by a seed-mediated technique and covered with mixed self-assembled monolayers

A micro FET-based immunosensor was developed for the determination of hemoglobin-A1c (HbA1c). The HbA1c/hemoglobin ratio is an important index in diabetes control. The sensor was fabricated by Complementary Metal-Oxide-Semiconductor Transistor (CMOS) and Micro Electronic Mechanical System (MEMS) techniques. The antibodies were immobilized via mixed self-assembled monolayers (SAMs) on a gold nanofilm. The nanofilm was deposited on a gold electrode by seed-mediated growth and gave a uniform and well distributed coverage. Nonspecific sites and interferences by noise were eliminated by covering the AuNPs with mixed SAMs. Compared to the immunosensor fabricated via the mixed SAMs method without gold nanofilm, the immunosensor displays a more than 2-fold sensitivity. The immunosensor is capable of detecting HbA1c and hemoglobin in hemolyzed and diluted whole blood, and results showed good agreement with the established clinical method.

Glycemic Control in the Intensive Care Unit and during the Postoperative Period

Glycemic Control in the Intensive Care Unit and during the Postoperative Period

Insufficient sensitivity of hemoglobin A1C determination in diagnosis or screening of early diabetic states

An International Expert Committee made recommendations for using the hemoglobin A1C (A1C) assay as the preferred method for the diagnosis of diabetes in nonpregnant individuals. A concentration of at least 6.5% was considered as diagnostic. It is the aim of this study to compare the sensitivity of A1C with that of plasma glucose concentrations in subjects with early diabetes or impaired glucose tolerance (IGT). We chose 2 groups of subjects who had A1C not exceeding 6.4%. The first group of 89 subjects had family histories of diabetes (MODY or type 2 diabetes mellitus) and had oral glucose tolerance test (OGTT) and A1C determinations. They included 36 subjects with diabetes or IGT and 53 with normal OGTT. The second group of 58 subjects was screened for diabetes in our Diabetes Clinic by fasting plasma glucose, 2-hour plasma glucose, or OGTT and A1C; and similar comparisons were made. Subjects with diabetes or IGT, including those with fasting hyperglycemia, had A1C ranging from 5.0% to 6.4% (mean, 5.8%). The subjects with normal OGTT had A1C of 4.2% to 6.3% (mean, 5.4%), or 5.5% for the 2 groups. The A1C may be in the normal range in subjects with diabetes or IGT, including those with fasting hyperglycemia. Approximately one third of subjects with early diabetes and IGT have A1C less than 5.7%, the cut point that the American Diabetes Association recommends as indicating the onset of risk of developing diabetes in the future. The results of our study are similar to those obtained by a large Dutch epidemiologic study. If our aim is to recognize early diabetic states to apply effective prophylactic procedures to prevent or delay progression to more severe diabetes, A1C is not sufficiently sensitive or reliable for diagnosis of diabetes or IGT. A combination of A1C and plasma glucose determinations, where necessary, is recommended for diagnosis or screening of diabetes or IGT.

Liquid Chromatography–Isotope Dilution–Mass Spectrometry as a New Basis for the Reference Measurement Procedure for Hemoglobin A1c Determination

Standardization of hemoglobin (Hb)A(1c) measurements is a process of considerable interest for quality assurance in diabetes management. To contribute to continuous quality improvement and fulfillment of the requirements for reference measurement procedures according to the standards of the International Organization for Standardization, we developed a calibration system of highest metrological order using isotope dilution-mass spectrometry with a reference material. Samples were prepared by enzymatic cleavage based on the IFCC reference measurement procedure for LC-MS analysis. After digestion the samples were spiked with [D7]-labeled glycated and nonglycated hexapeptides as internal standards for quantification. LC-MS analysis was performed by using a C12 reversed-phase column and a gradient of acetonitrile/H(2)O containing 0.1% formic acid. Calibration systems for HbA(1c) determination based on liquid chromatography-isotope dilution-mass spectrometry (LC-ID-MS) and on the IFCC reference measurement procedure were compared. A linear regression analysis demonstrated a correlation of r(2) = 1.00 between the 2 different calibration systems. Mean deviation was 5.5% for the calibration and 3.3% for hemolysate samples, with a mean expanded uncertainty of 4.9%. This LC-ID-MS procedure allows the current IFCC reference measurement procedure for HbA(1c) to be raised to a higher order of accuracy.

Oral Glucose Tolerance Testing in Asymptomatic Obese Children: More Questions than Answers

The prevalence of type 2 diabetes is increasing among youth and adults throughout the world, with striking rates of increase in rapidly developing countries (1–3). In adults, type 2 diabetes may remain undiagnosed for several years because hyperglycemia develops gradually and may not cause symptoms (2, 4). Therefore, it has been estimated that nearly 50% of prevalent cases of diabetes among adults remain undiagnosed (2, 5) Yet, it is also known that the risk for cardiovascular morbidity and mortality is increased well before the diagnosis of diabetes is made, including in subjects with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) (6). Therefore, the challenge of developing cost-effective approaches to the identification of undiagnosed diabetes among adults and the value of identifying IFG and IGT remain areas of substantial controversy. The challenge is even greater among youth. Although the obesity prevalence among children in the United States ranges from 10–30% (7), studies suggest that the prevalence of undiagnosed diabetes is surprisingly low (8), even among youth with multiple risk factors. Thus, there is little evidence to support wide-scale screening for diabetes among asymptomatic youth, because this would be a labor-intensive and expensive task with uncertain benefit, even when multiple risk factors are present. On the other hand, 40% of a cohort of eighth-graders had IFG, and rates of IFG and IGT are even higher among youth referred for evaluation in obesity clinics (9). Yet, the prognostic and therapeutic value of identifying IFG and IGT in youth is controversial, and the potential harm and long-term effects of labeling a population as abnormal are unknown. Furthermore, although there is evidence that the combination of IFG and IGT in youth is a strong predictor of progression to overt diabetes in the short term (10), no trial has yet established either that systematic screening for early glucose abnormalities in obese children or that early treatment improves health outcome. Nevertheless, there are clearly circumstances in which testing for undiagnosed diabetes, along with the identification of IFG and IGT may be desirable. For example, the identification of dysglycemia is important for establishing cohorts for research into the pathophysiology of these states in adolescents as well as for the exploration of potential approaches to intervention. Similarly, limited availability may require that clinical resources for the treatment of obese adolescents be focused on those most at risk for disease progression and comorbidities. However, a number of important questions remain. Who should be screened? Which test should be used? How often should the screening be repeated? Determination of hemoglobin A1c is not sufficiently sensitive to detect early or subtle abnormalities in glucose excursion and has no clear utility in identification of IFG and IGT. Furthermore, the utility of this simple measure of average glucose has been limited in the past by poor reproducibility and lack of standardization (11, 12). Measurement of fasting glucose allows the identification of both IFG and diabetes. However, ensuring adherence to fasting guidelines can be challenging in an obese adolescent population. Furthermore, the 2-h postload plasma glucose has been shown to have increased sensitivity for the diagnosis of both diabetes and IGT in adults (5) and children (9). In addition, it has been proposed that the oral glucose tolerance test (OGTT) is preferable to measurement of fasting glucose because IGT, which can only be identified through glucose challenge, has also been associated with an increased risk for development of cardiovascular disease (13, 14). However, the reproducibility of the test has been questioned. In this issue of the Journal, Ingrid Libman and her colleagues at the University of Pittsburgh (15) report a prospective study of the reproducibility of the OGTT in overweight children and confirm what has previously been reported in adults, namely that the reproducibility of the test is poor, particularly among those adolescents with the greatest degree of apparent abnormality. Clinically, these results mean that an isolated abnormal postload plasma glucose is not sufficient for the diagnosis of diabetes or impaired glucose metabolism in the pediatric population, further complicating the argument between the use of fasting glucose

Hemoglobin A1c determination in the A1C-Derived Average Glucose (ADAG) study

The A1C-Derived Average Glucose (ADAG) study was commenced to gain a better understanding of the relationship between HbA1c and average blood glucose and to investigate if HbA1c could be expressed in the same units as day-to-day glucose monitoring. Owing to the impact of the outcome of this study it was very important to determine HbA1c values with a minimum of uncertainty and as close as possible to the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) primary reference method, which is the only valid anchor of HbA1c standardization. Approximately 2300 samples were analyzed with four IFCC secondary reference methods. Additional off-line calibration with IFCC secondary reference material with assigned IFCC values was performed to improve the uncertainty in the HbA1c value determination. Additional off-line calibration improved the 95% confidence interval between the four different HbA1c methods at HbA1c of 6.00% from +/-0.28% (5.72%-6.28%) to +/-0.20% (5.80%-6.20%) and at HbA(1c) of 9.00% from +/-0.43% (8.57%-9.43%) to +/-0.24% (8.76%-9.24%). The HbA1c results used in the ADAG study were determined with the lowest uncertainty technically feasible by using four certified IFCC secondary reference methods and additional off-line calibration with IFCC secondary reference material.

An enzymatic method for the determination of hemoglobinA1C

Fructosyl peptide oxidase is a flavoenzyme that catalyzes the oxidative deglycation of N-(1-deoxyfructosyl)-Val-His, a model compound of hemoglobin (Hb)A(1C). To develop an enzymatic method for the measurement of HbA(1C), we screened for a proper protease using N-(1-deoxyfructosyl)-hexapeptide as a substrate. Several proteases, including Neutral protease from Bacillus polymyxa, were found to release N-(1-deoxyfructosyl)-Val-His efficiently, however no protease was found to release N-(1-deoxyfructosyl)-Val. Neutral protease also digested HbA(1C) to release N-(1-deoxyfructosyl)-Val-His, and then the fructosyl peptide was detected using fructosyl peptide oxidase. The linear relationship was observed between the concentration of HbA(1C) and the absorbancy of fructosyl peptide oxidase reaction, hence this new method is a practical means for measuring HbA(1C.).