Abstract

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 HbA₁ in the two female patients and slower in the male patient. The cDNA sequence and amino acid analyses of the haemoglobin α-chains and β-chains indicated the presence of the haemoglobin variant β 120 Lys→Gln in the two female patients and β 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.