Background Various factors may affect the accuracy of hemoglobin (Hb) A1c measurements that are widely used to monitor glycemic control in diabetic patients. This study was aimed to compare the values of HbA1c obtained by two different methods, Roche Tina-quant second and thirdgeneration HbA1c assays based on the turbidimetric inhibition immunoassay (TINIA), and high-performance liquid chromatography (HPLC) cation-exchange method used by Arkray Adams HA-8160 analyzer. Methods Measurements of HbA1c were carried out in blood samples from 2,917 patients using above-mentioned methods. Linear regression was used for the correlation analysis and linear equations. BlandAltman plots were performed from method comparison data using MedCalc statistical software. Results For the low control, the second generation Tina-quant assay had within-run and between-run CVs 0.8% and 0.9%; for the high control within-run and between-run CVs were 1% and 0.96%, respectively. HPLC method for the low control had within-run CV 1% and between-run CV 1.3%; for the high control within-run CV was 0.6% and between-run CV was 0.9%. Conclusion There was a good concordance between the results of TINIA and HPLC methods (y = 1.091x 0.363; r(2) = 0.96). J. Clin. Lab. Anal. 26:481-485, 2012. (C) 2012 Wiley Periodicals, Inc.