title: Unintended reporting of misleading Hb A(1c) values when using assays incapable of detecting hemoglobin variants.
abstract: BACKGROUND
  It is recommended that hemoglobin (Hb) A1c (Hb A1c) not be used to assess average glycemia in patients who have altered red blood cell life span.
  
  
  OBJECTIVE
  To investigate the frequency of reporting an Hb A1c value for Hb variant samples that do not include Hb A.
  
  
  METHODS
  Hb A1c samples (n = 500) were procured and screened for Hb variants that may affect Hb A1c interpretation (Hb SS, Hb SC, and Hb S-β-thalassemia). Five of each of these samples were tested by ion-exchange high-performance liquid chromatography, immunoturbidimetric assay, second-generation immunoturbidimetric assay, and affinity chromatography.
  
  
  RESULTS
  Eleven (2.2%) homozygous Hb SS, 6 (1.2%) Hb SC, and 5 (1.0%) Hb S-β-thalassemia samples were identified out of the 500 samples tested. Three of 4 instruments investigated in this study are known to not be plagued by analytic interference from these Hb variants but disturbingly reported Hb A1c values in the absence of Hb A.
  
  
  CONCLUSIONS
  The improved analytic specificity of Hb A1c platforms has by and large eliminated interferences from the most common heterozygous Hb variants. A consequence, however, is the potential for unintended reporting of Hb A1c results in the presence of homozygous and compound heterozygous Hb variants that lack Hb A and the inability to distinguish those samples not recommended to be used for patient care. The ability to identify samples harboring Hb variants that preclude the utility of Hb A1c may be beneficial in high prevalence populations.
authors.affiliation: From the Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia (Drs Rhea, Koch, Ritchie, Young, and Molinaro); the Department of Pathology and Laboratory Medicine, Grady Memorial Hospital, Atlanta, Georgia (Drs Koch and Young); the Department of Pathology, Hindu Rao Hospital, New Delhi, India (Dr Singh); and Laboratory Medicine, Quest Diagnostics, Atlanta, Georgia (Dr Burgess).
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Rhea
authors.forename: David
authors.initials: D
authors.lastname: Koch
authors.forename: James
authors.initials: J
authors.lastname: Ritchie
authors.forename: Harsh V
authors.initials: HV
authors.lastname: Singh
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Young
authors.forename: Tom
authors.initials: T
authors.lastname: Burgess
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Molinaro
mesh_terms: D003951:Diagnostic Errors; D014644:Genetic Variation / Q000235:genetics; D006442:Glycated Hemoglobin / Q000032:analysis*; D006403:Hematologic Tests; D006454:Hemoglobins / Q000145:classification* / Q000235:genetics; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D006943:Hyperglycemia / Q000097:blood* / Q000175:diagnosis*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D006442:Glycated Hemoglobin; D006454:Hemoglobins