title: Effects of 49 Different Rare Hb Variants on HbA1c Measurement in Eight Methods.
abstract: BACKGROUND
  Previous studies have shown interference with HbA1c measurement from the 4 most common heterozygous Hb variants (HbAS, HbAE, HbAC, and HbAD) with some assay methods. Here we examine analytical interference from 49 different less common variants with 7 different HbA1c methods using various method principles.
  
  
  METHODS
  Hb variants were screened using the Bio-Rad Variant or Variant II beta thal short program, confirmed by alkaline and acid electrophoresis, and identified by sequence analysis. The Trinity ultra2 boronate affinity high-performance liquid chromatography (HPLC) method and Roche Tinaquant immunoassay were used as primary and secondary comparative methods, respectively, since these methods are least likely to show interference from Hb variants. Other methods included were the Tosoh G7 and G8, Bio-Rad D-10 and Variant II Turbo, Diazyme Enzymatic, and Sebia Capillarys 2 Flex Piercing. To eliminate any inherent calibration bias, results for each method were adjusted using regression verses the ultra2 with nonvariant samples. Each method's calibration-adjusted results were compared and judged to be acceptable if within the 99% prediction interval of the regression line for nonvariant samples.
  
  
  RESULTS
  Almost all variant samples were recognized as such by the ion-exchange HPLC methods by the presence of abnormal peaks or results outside the reportable range. For most variants, interference was seen with 1 or more of the ion-exchange methods. Following manufacturer instructions for interpretation of chromatograms usually, but not always, prevented reporting of inaccurate results.
  
  
  RESULTS
  Laboratories must be cautious about reporting results when the presence of a variant is suspected.
authors.affiliation: Departments of Pathology & Anatomical Sciences and Child Health, University of Missouri, Columbia School of Medicine, Columbia, MO, USA littler@health.missouri.edu.
authors.forename: Randie R
authors.initials: RR
authors.lastname: Little
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: Sonia L
authors.initials: SL
authors.lastname: La'ulu
authors.affiliation: Departments of Pathology & Anatomical Sciences and Child Health, University of Missouri, Columbia School of Medicine, Columbia, MO, USA.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Hanson
authors.affiliation: Departments of Pathology & Anatomical Sciences and Child Health, University of Missouri, Columbia School of Medicine, Columbia, MO, USA.
authors.forename: Curt L
authors.initials: CL
authors.lastname: Rohlfing
authors.affiliation: Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Schmidt
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004586:Electrophoresis; D014644:Genetic Variation; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000235:genetics*; D006455:Hemoglobins, Abnormal / Q000032:analysis / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007118:Immunoassay; D016014:Linear Models; D015203:Reproducibility of Results; D017422:Sequence Analysis, DNA
chemical_list: D006442:Glycated Hemoglobin; D006455:Hemoglobins, Abnormal
keywords: HbA1c; accuracy; hemoglobin variants; interference