Effects of sample storage conditions on glycated hemoglobin measurement: evaluation of five different high...

Glycated hemoglobin, reported as hemoglobin A1c (HbA1c), is widely used as a measure of long-term glycemic control in patients with diabetes. The accuracy of measurements depends in part on proper storage of the sample prior to analysis.

Three whole blood (WB) samples at three HbA1c levels were collected and stored at -70 degrees C, -20 degrees C, 4 degrees C, room temperature (17-23 degrees C), and 37 degrees C. One aliquot from each temperature was analyzed by each method on days 1, 2, 3, 6, 7, 10, 14, 21, 28, and 57.

The Primus CLC (385 and 330) (Primus Corp., Kansas City, MO) showed stability of WB at -20 degrees C and 4 degrees C for 57 days, room temperature for 14 days, and 37 degrees C for 1 day. The Tosoh 2.2 Plus (Tosoh Bioscience, Inc., South San Francisco, CA) showed stability at -20 degrees C for 3 days, 4 degrees C for 14 days, room temperature for 3 days, and 37 degrees C for less than 24 h. With the Tosoh G7, results were acceptable at -20 degrees C for 10 days, 4 degrees C for 57 days, room temperature for 7 days, and 37 degrees C for less than 24 h. The Bio-Rad Variant (Bio-Rad Laboratories, Hercules, CA) showed stability at -20 degrees C for 6 days, 4 degrees C for 14 days, room temperature for 3 days, and 37 degrees C for less than 24 h. The Bio-Rad Variant II showed stability at -20 degrees C for 28 days, 4 degrees C for 57 days, room temperature for 7 days, and 37 degrees C for less than 24 h.

All methods either met or exceeded manufacturers' claims for stability. The CLC 385/330, Tosoh G7, and Bio-Rad Variant II high performance liquid chromatography methods showed better stability than the Tosoh 2.2 Plus and Bio-Rad Variant.