A diabetic patient with hemoglobin variant Hb Mito diagnosed from a change in HbA1c measurement method

Hemoglobin A1c (HbA1c) is used routinely to monitor long-term glycemic control in diabetic patients, but its accuracy can be affected adversely by the presence of Hb variants. More than 20 methods for determination of HbA1c are commercially available to clinical laboratories. We report a diabetic patient with Hb variant Hb Mito that was discovered incidentally following the use of a different method of HbA1c measurement. A 66-year-old Japanese woman with an 11-year history of type 2 diabetes was referred to our hospital with hyperglycemia diagnosed from a HbA1c level of 12.2 % measured by immunonephlometry method. Her HbA1c could not be measured by high-performance liquid chromatography (HPLC) in our hospital. Her blood glucose level was 273 mg/dl, and her glycosylated albumin was 33.9 %. She was diagnosed as having Hb Mito (β144 Lys → Glu) by mutation sequence analysis. This was the second case in Japan since the first case was reported in 1985 according of our survey of the literature.