The ability of glycated hemoglobin A(1c) (HbA(1c)) to predict diabetes is unknown, but could be evaluated by analyses on samples stored in biobanks. The stability of HbA(1c) in long-term stored samples is, however, unknown. Moreover, the effect of hemolysis on HbA(1c) in the general population is not assessed. To explore these questions HbA(1c) was determined in 3 groups (n = 717) of samples with storage times at -80 degrees C differing between 10 years and 2 months. The results were compared with HbA(1c) analyzed in fresh blood samples (n = 174). The subjects were free from diabetes and aged 40 to 60 years. HbA(1c) was analyzed by cation exchange high-performance liquid chromatography (HPLC). The mean HbA(1c) results for the fresh and long-term stored samples were 4.25% +/- 0.39 and 4.19% +/- 0.43, respectively (P = not significant [NS]). The HbA(1c) levels in fresh and 2-month stored samples were essentially equal. There was no correlation between HbA(1c) in the fresh samples and the hemolysis parameters reticulocytes, haptoglobin, or bilirubin. HbA(1c) is apparently stable in samples long-term stored at -80 degrees C and is not commonly affected by hemolysis in the general population. HbA(1c) analyzed on biobank samples could be used to assess the predictive value for future diabetes and relationship to other morbidity and mortality.