The influence of sample freezing at - 80 °C for 2-12 weeks on glycated haemoglobin (HbA1c) concentration assayed by HPLC method on Bio-Rad D-10®auto analyzer.
BACKGROUND
The aim of the study was to evaluate the effect of a single freeze/thaw cycle on HbA1cconcentrations measured by commercially available HPLC method.


METHODS
Study included 128 whole blood samples collected from diabetic patients (N = 60) and healthy volunteers (N = 68). HbA1cconcentrations were measured in fresh blood samples. Then samples were frozen at - 80 °C for up to 12 weeks. HbA1cwas assayed by ion-exchange HPLC method on Bio-Rad D-10®analyzer. Variables were compared using Wilcoxon and ANOVA Kruskal-Wallis tests. Bias between HbA1cmeasured in fresh and frozen samples was calculated. The comparability of HbA1cconcentrations was assessed by Bland-Altman plot.


RESULTS
Median (IQR) HbA1cconcentration was 45.3 (36.6-61.2) mmol/mol for fresh and 45.3 (36.6-60.6) mmol/mol for frozen/thawed samples. No significant difference in HbA1cconcentrations was found comparing fresh and frozen/thawed samples (P = 0.070) in the whole group, as well as in healthy and diabetic subjects. The median calculated bias between fresh and frozen/thawed samples was 0% in whole group and healthy subjects, and 1.19% in diabetic patients. No significant difference was found between the biases according to baseline HbA1c values (P = 0.150). The Bland-Altman plot analysis showed a positive bias of 0.4% (95% CI: - 2.8 - 3.7%), which indicates high compliance between HbA1cvalues and no relevant influence of sample freezing on clinical significance of HbA1cmeasurement.


CONCLUSIONS
Storage for up to 12 weeks at - 80 °C with a single freeze/thaw cycle does not affect HbA1cconcentrations measured with HPLC method on Bio-Rad D-10®analyzer.
Department of Laboratory Medicine, Nicolaus Copernicus University Collegium Medicum, Bydgoszcz, Poland.
Katarzyna
K
Bergmann
Department of Laboratory Medicine, Nicolaus Copernicus University Collegium Medicum, Bydgoszcz, Poland.
Grazyna
G
Sypniewska
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D005615:Freezing; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008875:Middle Aged
D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
diabetes; glycated haemoglobin; high performance liquid chromatography; preanalytical phase; sample storage