Abstract: Objective To evaluate the analysis performance of glycosylated hemoglobin A_1c(HbA_1c) detection by turbidimetric inhibition immunoassay (TINIA), to compare and evaluate the bias with ion exchange high performance liquid chromatography (IE-HPLC) for detecting HbA_1c, and to evaluate the influence of hemoglobin (Hb) E (HbE) on TINIA and IE-HPLC. Methods According to the methodology evaluation document (EP document) and relevant literatures from the Clinical and Laboratory Standards Institute (CLSI), the precision, accuracy, detection range, analysis interference and biological reference interval analysis of HbA_1c detection by TINIA were evaluated and verified. The comparison analysis and bias evaluation of TINIA and IE-HPLC for blood samples with normal Hb structure and blood samples in HbE patients were performed. The correlation with average blood glucose was analyzed. Results The within-run precision by TINIA was < 2.08%, the total imprecision was <2.94%, and the theoretical value with detection mean value was linearly correlated in the concentration range of 4.4%-18.3%(r=0.9994). When Hb, free bilirubin(FBiL), conjugated bilirubin(CBiL) and chyle(CH) concentrations were 9.9-49.6 μmol/L, 65.6-328.0 μmol/L, 65.6-328.0 μmol/L and 3 000-12 000 FTU, the difference percentage was <5%. The manufacturers provided reference interval (4.8%-5.9%) being suitable for clinical laboratories. For the blood samples with normal Hb structure, there was no statistical significance for HbA_1c detection between the 2 methods (P>0.05), and the results of HbA_1c detection by TINIA and IE-HPLC had good correlation (r²=0.999 2). For the blood samples with HbE concentration in the range of 5.4%-54.7%, the average bias by TINIA was -4.1%-1.9%, which was <5%. The interference was almost not affected by HbE, and the correlation of HbA_1c detection results with average blood glucose was good (r=0.998 8). While HbE >6.4%, the average bias of the detection value and the theoretical value for HbA_1c by IE-HPLC was 5.7%-278.7%, the difference percentage was >5%, and the expected theoretical results with the detection value had significant differences, and there was statistical significance between the 2 methods (P< 0.01). Conclusions The performance of HbA_1c detection by TINIA meets the performance requirements of clinical determination, and has a good correlation with that by IE-HPLC without interference by HbE. When HbE>6.4%, IE-HPLC for the detection of HbA_1c has interference, and there will be false increasing.

Key words: Glycosylated hemoglobin A_1c, Turbidimetric inhibition immunoassay, High performance liquid chromatography, Correlation analysis, Hemoglobin E disease