False elevation of hemoglobin A1 by hereditary persistence of fetal hemoglobin.

Measurement of glycosylated hemoglobin (HgA1) is frequently helpful in the management of patients with diabetes mellitus as it provides an index of average glucose control over the previous two to three months. The present case of a diabetic patient with a markedly increased hemoglobin A1 to 42% (normal 5.2-9.2%) with good glucose control prompted an investigation into the etiology of the increased hemoglobin A1 levels. Hemoglobin electrophoresis revealed that the patient had hereditary persistence of fetal hemoglobin. Hemoglobin F was quantitated and found to be responsible for 73% of the hemoglobin A1 determination. Hemoglobin F co-migrates with hemoglobin A1 on column chromatography and, when present in increased quantities, can falsely elevate the measured hemoglobin A1. Thus, if one utilizes the hemoglobin A1 assay to help guide management of patients with diabetes mellitus, it is important to remember that hemoglobin F can cause falsely elevated hemoglobin A1 levels.