Two Novel Haemoglobin Variants That Affect Haemoglobin A(1c) Measurement by Ion-Exchange Chromatography

Background: Haemoglobin (Hb) variants are well-known factors interfering with accurate HbA(1c) testing. This report describes two novel Hb variants leading to inappropriate quantification of HbA(1c) by ion-exchange chromatography.Methods: Glycated forms of novel Hb variants were recognised in the blood of two patients with diabetes mellitus screened by HbA(1c) ion-exchange chromatography. Dedicated high-resolution cation-exchange chromatography and subsequent DNA sequencing revealed the exact nature of the variants. Other common techniques for quantifying HbA(1c) were applied on both samples and haematological parameters were determined to judge possible pathology associated with the novel Hb variants.Results: A fraction of 15% of abnormal Hb was observed in a 37-year-old female. DNA sequencing revealed a heterozygous mutation in the alpha(1)-globin gene, resulting in a leucine-to-phenylalanine amino-acid substitution (HBA1: c.301C>T, p.Leu101Phe). We named this variant Hb Weesp. The other novel variant, Hb Haelen, presented as a 40% fraction in a 63-year-old male and resulted from a heterozygous amino acid substitution in the beta-globin gene (HBB: c.335T>C, p.Val112Gly). The presence of both Hb variants resulted in aberrant separation of the Hb components, leading to an inadequate quantification of HbA(1c).Conclusions: Close examination of HbA(1c) chromatograms revealed two novel, clinically silent Hb variants that interfere with HbA(1c) quantification. Healthcare providers need to be aware of the potential of such Hb variants when interpreting HbA(1c) results.