Abstract:

Objective To evaluate the quality of glycated hemoglobin A_1c（HbA_1c） determination and the comparability between different determination systems. Methods The data of external quality assessment（EQA） of HbA_1c in 2018 were collected. The participators were classified according to determination systems. The average of each specimen was calculated using robust algorithm as target value. The mean and inter-laboratory coefficient of variation（CV） of each group were calculated. The sigma metric of each group was calculated. The weighted sigma value was calculated for the specimens as well. Results Totally,268 laboratories took part in the program and reported results. A total of 4 groups were included for further analysis:group A（44 laboratories）,group B（87 laboratories）,group C（50 laboratories） and group D（26 laboratories）. The overall robust CV of the 5 specimens were 2.58%,1.85%,5.05%,2.70% and 4.77%,respectively. The robust CV of group A - group D were 1.80%-3.16%,1.72%-2.64%,1.32%-1.81% and 1.67%-3.38%,respectively. The averages of sigma metric of group A - group D were 1.19（-0.35-2.39）,2.42（1.66-3.25）,2.95（2.20-3.44） and 0.26（-2.76-2.92）. Three specimens in group C and one specimen in group B had a sigma metric >3. The weighted sigma metrics of the 5 specimens were 2.48,3.00,0.87,2.41 and 1.30,respectively. The average of the sigma level was 2. Conclusions The sigma metrics and robust algorithm can be used to evaluate the quality of HbA_1c determination in EQA deeply and objectively. The quality of HbA_1c determination in Zhejiang is not so satisfactory. Further step of quality management should be taken to achieve the goal of mutual recognition of determination results and meet the requirements for clinical diagnosis of diabetes mellitus.

Key words: Glycated hemoglobin A_1c, Diabetes mellitus, Six sigma, External quality assessment, Quality control