Increased fetal hemoglobin in insulin-treated diabetes mellitus contributes to the imprecision of glycohemoglobin measurements.

An increased prevalence of fetal hemoglobin (HbF) has been described in pediatric insulin-dependent patients. The popular electroendosmotic method for glycohemoglobin includes HbF. In an adult population comprising 50 insulin-treated and 57 non-insulin-treated diabetic patients and 57 control subjects, we measured HbF by HPLC and measured glycohemoglobin by both HPLC and an electroendosmotic method. Of the insulin-treated patients, 46% had concentrations of HbF > or = 0.5%, compared with 25% of non-insulin-treated patients and 23% of controls (P < 0.02). In the insulin-treated patients, the two glycohemoglobin methods correlated best when the HPLC measurements included HbF (r = 0.92 vs r = 0.84). Fructosamine concentrations correlated best with glycohemoglobin concentrations determined by methods that accounted for HbF. The true between-batch CV of the electroendosmotic assay increased (from 4.33% to 8.33%) when variable interpatient HbF concentrations were included. Thus, HbF must be considered when interpreting glycohemoglobin measured by an electroendosmotic method and when comparing it with other measures of glycemic control.