Components of Total Measurement Error for Hemoglobin [A.Sub.1C] (Technical Briefs) (Clinical Report‪)‬

The Diabetes Control and Complications Trial (DCCT) and the UK Prospective Diabetes Study (UKPDS), undertaken in people with type 1 and 2 diabetes, respectively (1, 2), established the significance of glycohemoglobin (gHb), and in particular hemoglobin [A.sub.1c] ([HbA.sub.1c], as a prognostic indicator for long-term micro- and macrovascular complications. However, the [HbA.sub.1c] measured during the DCCT and UKPDS represents a gHb fraction characterized by its retention time on cation-exchange HPLC rather than its unique chemical structure (deoxyfructosylhemoglobin). Accordingly, the DCCT [HbA.sub.1c] procedure represents a selective, but not a specific assay method (3). Because no definitive or reference method exists for quantification of [HbA.sub.1c] (4), the American Diabetes Association (ADA), in collaboration with the Association of Clinical Chemists, implemented the National Glycohemoglobin Standardization Program (NGSP) (5) to standardize [HbA.sub.1c] values determined by methods different from that used in the DCCT. The ADA (6) now states that their recommended [HbA.sub.1c] thresholds, with respect to patient management goals, are valid only for NGSP-certified methods.