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

AimTo validate the stability of glycated haemoglobin (HbA1c) measurements in blood samples stored at − 20 °C for up to one month.MethodsThe 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.ResultsThe 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.ConclusionsHbA1c levels are relatively stable up to 2 weeks, if blood samples are stored at − 20 °C.