Stability and reliability of glycated haemoglobin measurements in blood samples stored at -20°C

Abstract

Aim: To validate the stability of glycated haemoglobin (HbA1c) measurements in blood samples stored at -20°C for up to one month.

Methods: The study group comprised 142 type 2 diabetic subjects visiting a tertiary centre for diabetes at Chennai city in south India. The HbA1c assay was done on a fasting blood sample using the Bio-Rad Variant machine on Day 0 (day of blood sample collection). Several aliquots were stored at -20°C and the assay was repeated on the 3rd, 7th, 15th, and 30th day after the sample collection. Bland-Altman plots were constructed and variation in the HbA1c levels on the different days was compared with the day 0 level.

Results: The median differences between HbA1c levels measured on Day 0 and the 3rd, 7th, 15th, and 30th day after blood collection were 0.0%, 0.2%, 0.3% and 0.5% respectively. Bland-Altman plot analysis showed that the differences between the day '0' and the different time points tend to get larger with time, but these were not clinically significant.

Conclusions: HbA1c levels are relatively stable up to 2weeks, if blood samples are stored at -20°C.

Keywords: Asian Indians; HbA1c; Reliability; Stability; Stored samples.