Assessment of stability of HbA1c levels in human whole blood samples using immunoassays

Abstract

Hemoglobin A1c (HbA1c) levels in whole blood samples are commonly used to diagnose diabetes and monitor the effectiveness of glycemic control. However, there have not been many studies evaluating changes in HbA1c concentration under different storage conditions and analytical methods. The purpose of this study was to evaluate the stability of %HbA1c stored at different temperature conditions using immunoassays in order to improve the quality of HbA1c test. Whole blood samples collected from 10 healthy volunteers were anticoagulated with K2 EDTA and stored at the following temperatures: 20-25 °C, 2-8 °C, and -20 °C. %HbA1c in human whole blood samples at each time point was determined simultaneously on Standard F Analyzer (%HbA1c-S) with reagent kit based on a reflectometry and immunoassay technology, and Erba XL640 system (%HbA1c-E) used immunoturbidimetric method, respectively. %HbA1c was assessed as stable when the difference in HbA1c level at the later time point was not statistically significant (p >0.05) compared with baseline (T0). Results showed that a positive correlation between %HbA1c-S and %HbA1c-E at T0 (r=0.9996) was observed at room temperature. %HbA1c-S was stabilized for 24 hours at 20-25 °C, for 2 days at 2-8°C and for more than 1 month at -20 °C. %HbA1c-E was stable for 12 hours at 20-25°C; less than 1 day at 2-8°C, and less than 1 month at -20°C. In conclusion, human whole blood samples for HbA1c determination can be stored for up to 1 month at -20°C.