Interference with hemoglobin A1c determination by the hemoglobin variant shelby

Hemoglobin variant carrier status was found in a 46-year-old African American man following detection of a falsely elevated hemoglobin A(1c) (HbA(1c)) by ion-exchange high-performance liquid chromatography (HPLC, VARIANT A(1c), Bio-Rad Laboratories, Hercules, CA). Additional analysis of the hemoglobin variant using the Beta Thal Short program (Bio-Rad) revealed an unknown peak with a retention time of 4.84 minutes and a proportion of 263%. No mass shift in a-globin or P-globin proteins was observed by mass spectrometry. DNA sequencing revealed a missense mutation in I beta-globin allele corresponding to the hemoglobin Shelby trait. The patient was asymptomatic with a normal hemoglobin value of 13.6 g/dL (136 g/L) but had increased target cells on a peripheral blood smear An alternative method for HbA(1c) determination using boronate-affinity HPLC provided a value of 3.9% (0.04; reference range, 4.0%-69% [0.04-0.07]), more consistent with the patient's recent blood glucose values in the normal range.