Objective: Measurement of HbA1c is widely used in patients with diabetes mellitus as a monitor of retrospective glycemic control. Currently, more than 30 different methods are commercially available to measure HbA1c and these methods vary in the fraction of Hb measured and the interferants. The aim of this study was to study the performance of immunoturbidimetric method against the high performance liquid chromatography (HPLC) method as the reference.

Materials and Methods: Control sera were used to define within-day and between-day precision. Samples from 144 subjects were collected and HbA1c levels were determined (double-blind, paralel manner) using both systems.

Results: Intra- and the inter-assay C Vs (coefficient of variation) of assay systems were < 3% with the immunoturbidimetric method ( HbA1c values 5.1% and 8.2% ) and and < 2% with the HPLC method (HbA1c values 5.1% and 10.5%) , respectively. There was significant difference between HbA1c results measured with HPLC (8.9%±2.8) and turbidimetric immuno-inhibition (8.2%±2.8) methods (p<0.01). Accuracy was evaluated in the selected fresh sera with HbA1c levels between 5.1-17.5 %. Correlation coefficient was r=0.987 and the regression equation was [Dimension HbA1c (%) = 0.974xHPLC (%) -0.442] acceptable.

Conclusion: Although the results of immunoturbidimetric assay system is comparable to HPLC system; depending on the importance of small changes in HbA1c levels in therapy one method should be chosen for monitoring diabetic patients.