Intra‐Laboratory and Inter‐Laboratory Variations Analysis for HbA1c Assays in China: Using Internal Quality Control and External Quality Assessment Data

OBJECTIVES: With the worldwide increase of diabetes mellitus prevalence, ensuring the performance of HbA1c assays is essential. Internal quality control (IQC) and external quality assessment (EQA) serve as critical components of quality assurance systems and provide comprehensive performance assessment. We aimed to evaluate the intra-laboratory and inter-laboratory variations of HbA1c assays using EQA and IQC data. METHODS: A total of 326 laboratories continuously participating in the HbA1c EQA program from 2020 to 2023 were included, of which 168 laboratories reported IQC data voluntarily. Acceptance rates and bias were evaluated at three levels: per sample, per year, and per manufacturer. Intra-laboratory and inter-laboratory variations were assessed according to biological variation (BV) criteria and clinical guidelines. RESULTS: The mean acceptance rates for 20 EQA samples were 48.5%, 77.8%, 86.7% within optimum, desirable, minimum BV criteria. Annual average acceptance rates increased from 91.8% to 96.9% based on EQA criterion. The absolute manufacturer-specific bias varied from 0.02% to 4.1%. By 2023, the overall inter-laboratory variation significantly decreased to 2.1%-2.6%. The median intra-laboratory variations reduced from 1.6% to 1.4% at the low QC level and from 1.2% to 1.0% at the high QC level. 58.9% and 79.8% of laboratories achieved an intra-laboratory CV < 1.5% for low and high QC levels, respectively. CONCLUSIONS: Both inter-laboratory and intra-laboratory variations of HbA1c measurement have significantly decreased over the years. However, the difference among manufacturers still exists, and ongoing efforts are required to fully comply with clinical guideline requirements.