A case of hemoglobin C in a non-diabetic elderly japanese diagnosed with falsely high HbAlc levels

Abstract

Several methods are available for measuring HbAlc in Japan, including high-performance liquid chromatography (HPLC), immunoassays and enzymatic assays. HPLC is commonly used in many facilities in Japan, but recently, the numbers of enzymatic assays and immunoassays have been increasing. We herein report a case of hemoglobin C (HbC) considered to involve diabetic mellitus because of falsely high levels of HbAlc on an immunoassay. A 74-year-old woman visited our hospital for the re-examination of HbAlc, as she was recommended to take medicine for diabetes mellitus by her local doctor. An HbAlc analysis using HPLC in our hospital showed an abnormally low value that was within the reference value using the enzymatic assay. Glycated albumin levels were in the normal range. A genetic analysis showed the presence of a heterozygous miss-sense mutation of the β-globin chain, which we diagnosed as HbC. HbC is frequently recognized in African populations as hemoglobinopathy, but it is rare in Japan. However, its frequency might increase in the future with internationalization. We should carefully evaluate the HbAlc level when we detect a discrepancy between HbAlc and the expected glucose level using a glucose tolerance evaluation.