Assessing agreement between the three common clinical measurement methods of HbA1c

Reliable measurement of hemoglobin A1c (HbA1c) has great importance in the diagnosis and monitoring of diabetes mellitus. The aim of the present study was to compare the performance parameters of the three common methods of HbA1c assay, including the Roche, Sebia and TOSOH G8 systems. We studied 120 patients referred to a clinical laboratory for HbA1c assay. The blood samples were analyzed with the Roche, Sebia and TOSOH G8 systems based on immunoassay, capillary electrophoresis, and ion-exchange chromatography techniques, respectively. The Spearman and the Passing-Bablok regression,as well as the Bland-Altman plots, were used to compare these methods. For each assay, the patients' classification was evaluated at the three cut-points of 6.5, 7, and 8% and the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the methods were estimated. Our results showed that there were good correlations and agreement between the methods. We found a mean difference of 0.07% for the TOSOH G8 vs. Roche, 0.06% for the TOSOH G8 vs. Sebia and - 0.01% for the Roche vs. Sebia. The methods represented very low bias, indicating the good accuracy of the results. The sensitivity and specificity of the methods were comparable as well. The three methods also performed similarly in the classification of patients at the proposed cut-off points. Based on our results, the Roche, Sebia and TOSOH G8 systems showed a very high level of agreement with comparable performance parameters and yielded similar and accurate classification of diabetic patients. Therefore, these methods can be used interchangeably.