External quality assessment and internal quality control analysis of glycated hemoglobin A1c in laboratories of 110 medical institutions with mutual recognition agreement in Beijing-Tianjin-Hebei region

Abstract

Objective To evaluate the comparability of glycated hemoglobin A1c (HbA1c) testing results among mutual recognition laboratories by analyzing the results of external quality assessment (EQA) and internal quality control (IQC) of 110 mutual recognition laboratories in Beijing-Tianjin-Hebei region. Methods Five lots of EQA materials were distributed to the participant laboratories by express mail services (EMS). Laboratories should test the samples within a specific time, and submit results via web-based EQA software. Meanwhile, IQC data in January 2016 should also be reported though web. Then the EQA results without grouping were evaluated by traditional statistical method and simple robust statistical method. Finally, the current coefficient of variation (CV) and cumulative CV of different groups divided by different analytical systems were evaluated against imprecision criteria for IQC recommended by Measurement of Hemoglobin A1c (WS/T461-2015). Results Total of 110 mutual recognition laboratories participated in this EQA scheme and 95 laboratories submitted IQC information. As for EQA results, the percentage of laboratories of which the EQA results were acceptable was 90.9% (100/110) by use of traditional statistical method. When simple robust statistical method were applied, more than 92.3% (107/110) of the laboratories got a simple robust statistical Z score ︱Z︱≤2; less than 4.0% of the laboratories got︱Z︱≥3; only 4(3.64%) laboratories got a ︱Z︱≥3 in two or more lots. EQA results of 4(3.6%) laboratories were unacceptable according to the two kinds of statistical methods. As for IQC data, only 57(60.0%) laboratories tested IQC material of two concentration levels. If the criteria of CV<2% and CV<3% were employed, the range of overall pass rates was 51.2%-66.2% and 77.4%-85.3%, respectively. Conclusions Some laboratories still cannot meet the requirements for mutual recognition, the EQA results are satisfactory, but IQC performance should be improved. It is suggested that laboratories with unacceptable performance should take corrective action or their qualifications for mutual recognition could be canceled. Key words: Hemoglobin A, glycosylated; Quality control; Laboratory proficiency testing; Quality assurance, health care