Estimation of biological variation and reference change value of glycated hemoglobin (HbA1c) when two analytical methods are used

Available data on biological variation of HbA1c revealed marked heterogeneity. We therefore investigated and estimated the components of biological variation for HbA1c in a group of healthy individuals by applying a recommended and strictly designed study protocol using two different assay methods. Each month, samples were derived on the same day, for three months. Four EDTA whole blood samples were collected from each individual (20 women, 9 men; 20–45years of age) and stored at −80°C until analysis. HbA1c values were measured by both high performance liquid chromatography (HPLC) (Shimadzu, Prominence, Japan) and boronate affinity chromatography methods (Trinity Biotech, Premier Hb9210, Ireland). All samples were assayed in duplicate in a single batch for each assay method. Estimations were calculated according to the formulas described by Fraser and Harris. The within subject (CVI)–between subject (CVG) biological variations were 1.17% and 5.58%, respectively for HPLC. The calculated CVI and CVG were 2.15% and 4.03%, respectively for boronate affinity chromatography. Reference change value (RCV) for HPLC and boronate affinity chromatography was 5.4% and 10.4% respectively and individuality index of HbA1c was 0.35 and 0.93 respectively. This study for the first time described the components of biological variation for HbA1c in healthy individuals by two different assay methods. Obtained findings showed that the difference between CVA values of the methods might considerably affect RCV. These data regarding biological variation of HbA1c could be useful for a better evaluation of HbA1c test results in clinical interpretation. •For the first time by two different assay methods.•The current lack of reliable data regarding biological variation.•Highly crucial for optimal patient care.•How much of this change in HbA1c is secondary to biological variation.