Abnormal haemoglobins, Hb Takamatsu and Hb G-Szuhu, detected during the analysis of glycated haemoglobin (HbA(1C)) by high performance liquid chromatography

Background—During medical checkups of two unrelated female outpatients during their annual health examination and one male inpatient suffering from cardiac failure the glycated haemoglobin (HbA(1C)) concentrations measured by high performance liquid chromatography (HPLC) were low, in spite of normal fasting plasma glucose concentrations. However, HbA(1C) concentrations measured by latex immunoagglutination and fructosamine concentrations were within the normal range. Method—Investigations were performed to elucidate the reasons for these discrepancies. Results—Abnormal haemoglobins, Hb Takamatsu and Hb G-Szuhu, were found. The HPLC chromatogram showed an additional peak near HbA(1a+b), which resulted in falsely low HbA(1C) concentrations. Isoelectric focusing analysis of the patients' haemoglobin disclosed abnormal haemoglobins, which migrated faster than normal HbA(1) in the two female patients and slower in the male patient. The cDNA sequence and amino acid analyses of the haemoglobin α-chains and ß-chains indicated the presence of the haemoglobin variant ß 120 Lys→Gln in the two female patients and ß 80 Asn→Lys in the male patient; that is, Hb Takamatsu and Hb G-Szuhu. Conclusions—These cases show how these silent haemoglobin variants can result in falsely low HbA(1C) concentration readings when using HPLC. Key Words: abnormal haemoglobin • high performance liquid chromatography • glycated haemoglobi