BACKGROUND: The purpose of this study was to evaluate the performance and agreement among HbA(1c) values measured using selected analyzers certified by the National Glycohemoglobin Standardization Program (NGSP) and standardized by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). METHODS: HbA(1c) determined using D-10 (Bio-Rad, USA), Variant II Turbo (Turbo; Bio-Rad, USA), Cobas Integra 800 (Integra; Roche, Switzerland) and Afinion AS100 (Afinion; Axis-Shield, Norway) were compared with each other. Precision and method comparisons with Deming regression were evaluated according to CLSI recommendations. We also compared the HbA(1c) values obtained with each analyzer using either IFCC or NGSP methods by correlation analysis and kappa statistics. RESULTS: The repeatability and method/device precisions of D-10 and Afinion were acceptable. The correlation coefficients of HbA(1c) were 0.986 for D-10 vs. Afinion, 0.997 for D-10 vs. Turbo, 0.988 for D-10 vs. Integra, and 0.991 for Integra vs. Afinion. The average biases of HbA(1c) Afinion (IFCC) and HbA(1c) Integra (IFCC) against HbA(1c) D-10 (NGSP) were -1.90% and -1.79%, respectively. Kappa agreement statistics for the three diabetic control group HbA(1c) values of "less than 6.5%," "6.5%-7.5%," and "greater than 7.5%" for D-10 vs. Turbo, D-10 vs. Integra, and D-10 vs. Afinion were 0.872, 0.836, and 0.833, respectively. CONCLUSIONS: The strong correlations and good clinical agreements of HbA(1c) between each analyzer expressed in terms of either NGSP or IFCC-derived NGSP indicate that these analyzers can be used interchangeably.
Blood Chemical Analysis/instrumentation/methods/standards ; Diabetes Mellitus/therapy ; Hemoglobin A, Glycosylated/*analysis/standards ; Humans ; Reproducibility of Results

After the relationship between glycemic control and the HbA1c concentration was demonstrated, many tests have been developed to determine the HbA1c concentration. The test results are standardized to the International Federation of Clinical Chemistry (IFCC) Reference Measurement Procedure (RMP) in harmony with the efforts of the National Glycohemoglobin Standardization Program (NGSP). The longitudinal use of the test requires strict quality management including accreditation of the laboratory, a dedicated internal control design, participation in an external quality assessment (EQA) program (proficiency test), and careful consideration of pre- and post-analytical aspects of the test. Performance goals for optimizing determination of the HbA1c concentration have been described. As an index of long-term glycemic control and a risk predictor, the HbA1c concentration is an indispensable part of routine management of diabetes. Because of the improving quality of the test, the HbA1c concentration is being increasingly applied in the diagnosis of diabetes. There are, however, concerns of this application in point-of-care settings. The HbA1c concentration is also used to achieve stringent control in pregnant diabetic patients. Strict standardization enables the definition of universal reference values and clinical decision limits. This review describes the present status of analytical and clinical aspects of determining the HbA1c concentration and highlights the challenges involved.
Diabetes Mellitus/blood/diagnosis ; Hemoglobin A, Glycosylated/*analysis/standards ; Humans ; Immunoassay/standards ; Point-of-Care Systems ; Quality Control

In 2010, the Japan Diabetes Society decided to introduce the National Glycohemoglobin Standardization Program (NGSP) values into clinical practice. Accordingly, NGSP Certification of Japanese manufacturers of HbA(1c)-related diagnostic reagents and instruments was initiated in February, 2012, through an NGSP network laboratory, the Asian Secondary Reference Laboratory (ASRL) #1. Traceability to the NGSP reference system can be endorsed by manufacturer certification, as well as by the College of American Pathologists (CAP) survey. Nevertheless, only a few manufacturers participate in the CAP survey in Japan. Thus, proficiency testing (PT) was proposed and executed by ASRL #1. Single-donor whole-blood samples were used for the PT. The participated measurement systems were NGSP certified. Twenty-two laboratories obtained certification through ASRL #1; 2 through the Secondary Reference Laboratory (SRL) #8; and 9 through the SRL #9. The combination plots of the bias data in this PT and in the NGSP certification performed in March and May in 2012 were consistent with each other: mean NGSP values at each level agreed well with the target value. In conclusion, PT using whole blood is useful in endorsing NGSP certification.
Asia ; Chromatography, High Pressure Liquid ; Enzyme Assays ; Hemoglobin A, Glycosylated/*analysis/standards ; Humans ; Immunoassay ; Japan ; Laboratory Proficiency Testing/*standards ; Quality Control ; Reference Standards ; Republic of Korea ; Societies, Scientific

BACKGROUND/AIMS: The application of glycated hemoglobin (HbA1c) for the diagnosis of diabetes is currently under extensive discussion. In this study, we explored the validity of using HbA1c as a screening and diagnostic test in Chinese subjects recruited in Nanjing, China. METHODS: In total, 497 subjects (361 men and 136 women) with fasting plasma glucose (PG) > or = 5.6 mmol/L were recruited to undergo the oral glucose tolerance test (OGTT) and HbA1c test. Plasma lipid, uric acid, and blood pressure were also measured. RESULTS: Using a receiver operating characteristic curve, the optimal cutoff point of HbA1c related to diabetes diagnosed by the OGTT was 6.3%, with a sensitivity and specificity of 79.6% and 82.2%, respectively, and the area under the curve was 0.87 (95% confidence interval, 0.83 to 0.92). A HbA1c level of 6.5% had a sensitivity and specificity of 62.7% and 93.5%, respectively. When comparing the HbA1c > or = 6.5% or OGTT methods for diagnosing diabetes, the former group had significantly higher HbA1c levels and lower levels of fasting and 2-hour PG than the latter group. No significant difference was observed in the other metabolism indexes between the two groups. CONCLUSIONS: Our results suggest that HbA1c > or = 6.5% has reasonably good specificity for diagnosing diabetes in Chinese subjects, which is in concordance with the American Diabetes Association recommendations.
Aged ; Analysis of Variance ; *Asian Continental Ancestry Group ; Biological Markers/blood ; Blood Glucose/analysis ; China/epidemiology ; *Chromatography, High Pressure Liquid/standards ; *Chromatography, Ion Exchange/standards ; Diabetes Mellitus, Type 2/blood/*diagnosis/ethnology ; Fasting/blood ; Female ; Glucose Tolerance Test/standards ; Hemoglobin A, Glycosylated/*analysis ; Humans ; Male ; Mass Screening/*methods/standards ; Middle Aged ; Predictive Value of Tests ; ROC Curve ; Reference Standards ; Reproducibility of Results ; Sensitivity and Specificity