title: Two novel haemoglobin variants that affect haemoglobin A1c measurement by ion-exchange chromatography.
abstract: BACKGROUND
  Haemoglobin (Hb) variants are well-known factors interfering with accurate HbA1c testing. This report describes two novel Hb variants leading to inappropriate quantification of HbA1c by ion-exchange chromatography.
  
  
  METHODS
  Glycated forms of novel Hb variants were recognised in the blood of two patients with diabetes mellitus screened by HbA1c 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 HbA1c 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 α1-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 β-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 HbA1c.
  
  
  CONCLUSIONS
  Close examination of HbA1c chromatograms revealed two novel, clinically silent Hb variants that interfere with HbA1c quantification. Healthcare providers need to be aware of the potential of such Hb variants when interpreting HbA1c results.
authors.forename: Michael
authors.initials: M
authors.lastname: Bots
authors.forename: An K
authors.initials: AK
authors.lastname: Stroobants
authors.forename: Barend
authors.initials: B
authors.lastname: Delzenne
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Soeters
authors.forename: Johan E
authors.initials: JE
authors.lastname: de Vries
authors.forename: Cas W
authors.initials: CW
authors.lastname: Weykamp
authors.forename: Roelf J C
authors.initials: RJ
authors.lastname: Norg
authors.forename: Martijn
authors.initials: M
authors.lastname: Veldthuis
authors.forename: Rob van
authors.initials: Rv
authors.lastname: Zwieten
mesh_terms: D000328:Adult; D001774:Blood Chemical Analysis / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange / Q000379:methods*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000302:isolation & purification; D006455:Hemoglobins, Abnormal / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation
chemical_list: D006442:Glycated Hemoglobin; D006455:Hemoglobins, Abnormal