Effect of Elevated levels of Hemoglobin F on HbA1c Measurements: Evaluation of Three HbA1c Assays
Introduction: Accurate measurement of HbA1c is crucial in the diabetic control and diagnosis. Elevated levels of HbF are reported to falsely decrease the HbA1c result and effect is very much method dependent. Material & Methods: Commercial assay methods G8 HPLC analyzer and DCA 2000 were evaluated. G8 is an ion exchange, high performance liquid chromatography (HPLC) method that measures the HbA1c as a percentage of total amounts of hemoglobin present in the sample. Two whole blood EDTA patient pools were prepared with HbA1c concentrations in the normal (5% to 7%) and abnormal range (7% to 8%). All chromatograms from
G8 were reviewed for any change in the peak resolution time due HbF concentrations. Results: The mean value for normal and abnormal pool was 5.8% and 7.5% resp. HbF showed no interference on Tosoh HbA1c results up to 30% in normal pool and up to 25% in abnormal pool. Observed difference between G8 and both Dimension EXL and DCA 2000 was clinically significant beyond 10% HbF. Conclusion: Accurate measurement of HbA1c is crucial for the decision making for diabetic control and diagnosis. The allowable error proposed by College of American Pathologist (CAP) is 6% therefore, appropriate knowledge about factors interfering with HbA1c results is absolutely important.