Abnormal haemoglobins, Hb Takamatsu and Hb G-Szuhu, detected during the analysis of glycated haemoglobin (HbA_1C) by high performance liquid chromatography

Y Moriwaki¹, T Yamamoto¹, Y Shibutani², T Harano³, S Takahashi¹ and T Hada¹

¹ Third Department of Internal Medicine, Hyogo College of Medicine, Mukogawa-cho 1–1, Nishinomiya, Hyogo 663–8501, Japan
² Division of Endocrinology, Nishi-Kobe Medical Centre, Koujidai 5-7-1, Nishi-ku, Kobe Hyogo 651–22, Japan
³ Department of Biochemistry, Kawasaki Medical School, Matsushima 577, Kurashiki, Okayama 701–0192, Japan

Correspondence to:
Dr Moriwaki tetsuya{at}hyo-med.ac.jp

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 -chains and ß-chains indicated the presence of the haemoglobin variant ß 120 LysGln in the two female patients and ß 80 AsnLys 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 haemoglobin

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