Quality Control and the Task of Improving the Measurement of Glycated Hemoglobin A1c and Glycated Albumin Using Clinical Samples. A Report from The Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes

Abstract

We evaluated the quality control status of glycated hemoglobin A1c (HbA1c) and glycated albumin (GA) at The Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes. We used the absolute relative difference (ARD) between one centralized laboratory value and the values from four clinical samples at each Institute. The methods that each method used for the measurement of HbA1c and GA were investigated and we determined whether the measurement was conducted in-hospital. Additionally, for GA, the number of samples at each institution and the frequency of internal quality control by existing calibrators were investigated. HbA1c sample measurements were conducted in-hospital in 98 % of the cases and 86 % were measured using the HPLC method. For GA, 78 % of measurements were conducted in-hospital, and the frequency of quality control was 1.9 (0-6) times per month. The mean ARD of GA was 2.65 %, which was significantly higher than the mean ARD of HbA1c (1.91 %). The ARD of GA was higher in institutes with less frequent internal quality control and fewer samples. Both HbA1c and GA were well controlled in terms of accuracy, but it was considered important to ensure the frequency of internal quality control for GA measurement. The analysis of clinical specimens was useful for continuous external quality control.