National External Quality Assessment Scheme for HbA1c:Evaluation of Performance Using Assigned Values

Accuracy and reliability of HbA1c assays are essential for diagnosis and monitoring diabetes mellitus (DM). To support the Thai Ministry of Public Health goals on a decrease in numbers and mortality rates of DM cases by 2025, National External Quality Assessment Scheme (NEQAS) for HbA1c was established to evaluate quality of HbA1c assays of public and private laboratories in the country. HbA1c results obtained from each laboratory were evaluated by comparing with target value assigned by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference system, Netherlands. Four whole blood samples per cycle (2 cycles per year) were distributed to 101 participants’ laboratories by a cold chain system. Participants’ results were evaluated with the IFCC assigned value for satisfactory performance of accuracy (% difference ≤ ± 10%). Participating laboratories demonstrated satisfactory performance of accuracy with high percentages, ranging from 89.00-97.00, depending on each sample. The proportion of laboratories that had within-laboratory and between-laboratory precision in acceptable limits (|Z score| < 3.00) were 97.92 and 92.71%, respectively, and overall Mean Bias ≤ 0.12, SD ≤ 0.59, and % CV ≤ 7.19. In addition, performance evaluation using IFCC assigned values could indicate that differences in principles and instrument platforms might have an impact on HbA1c analysis. Our finding demonstrated that laboratory participation in NEQAS for HbA1c is essential for quality improvement on laboratory and its outcome with high accuracy, resulting in benefits for care and treatment for DM patients.