Clinical implications of labile HbA1 as assayed by the electrophoretic method.

The labile fraction of glycosylated haemoglobin (HbA1) was detected using an agar gel electrophoretic method; complete removal of this fraction was obtained by prior incubation of blood for 4 h in isotonic sodium chloride solution at 37 degrees C. Intra-individual variation in pre- and post-incubation HbA1 measurements was considerable, but no greater than would be predicted from methodological imprecision (within-plate CV = 2.8%, between-plate CV = 4.1%). In blood from 13 diabetics with a wide spectrum of glycaemic control, mean labile HbA1 was only 5% of total HbA1 (range -4.4% to + 15.6%); the size of the labile fraction was proportional to total HbA1 and plasma glucose concentrations. Sodium chloride incubation did not affect clinically appropriate classification of results. It is concluded that total HbA1 is adequate for clinical purposes. The colorimetric method was found to be less convenient and less precise.