title: Utilization of assay performance characteristics to estimate hemoglobin A1c result reliability.
abstract: BACKGROUND
  Allowable total error (TE(a)) goals for hemoglobin (Hb) A(1c) require minimal assay imprecision and bias and implementation of a robust QC monitoring program. Here, we compare the combined influence on the risk of reporting unreliable results of TE(a) goals, a routine QC practice, and assay performance characteristics of 6 Hb A(1c) instruments across 4 academic medical centers.
  
  
  METHODS
  The CLSI protocols EP-5 and EP-9 were applied to investigate Hb A(1c) result imprecision and bias on the Variant II Turbo and Variant II (Bio-Rad), G8 (Tosoh), Capillarys 2 Flex Piercing (Sebia), COBAS Integra 800 (Roche), and DCA Vantage (Siemens). Patient-weighted σ values and the risk of reporting unreliable Hb A(1c) results were determined for each assay at TE(a) specifications of 5%, 6%, and 7%.
  
  
  RESULTS
  A large range of patient-weighted σ values spanning 0.5 orders of magnitude at a 6% TE(a) was observed. Although imprecision for all instruments was <3%, bias impacted the majority of the σ changes observed. Estimates for reporting unreliable results varied almost 500-fold based on analytical performance alone.
  
  
  CONCLUSIONS
  Considerable differences in the probability of reporting unreliable Hb A(1c) results between different NGSP (formerly the National Glycohemoglobin Standardization Program)-certified platforms were observed. At a 6% TE(a), our study indicates all but the Capillarys 2 Flex Piercing requires that the maximum affordable QC be run. Risk estimates for individual laboratories' Hb A(1c) methods can be used to assess QC practices and residual risk of an unreliable Hb A(1c) result.
authors.affiliation: Vanderbilt University, Nashville, TN;
authors.forename: Alison
authors.initials: A
authors.lastname: Woodworth
authors.affiliation: University of North Carolina, Chapel Hill, NC;
authors.forename: Nichole
authors.initials: N
authors.lastname: Korpi-Steiner
authors.affiliation: University of Louisville, Louisville, KY;
authors.forename: James J
authors.initials: JJ
authors.lastname: Miller
authors.affiliation: UMass Memorial Medical Center, Worcester, MA;
authors.forename: Lokinendi V
authors.initials: LV
authors.lastname: Rao
authors.affiliation: Bio-Rad Quality System Division, Plano, TX;
authors.forename: John
authors.initials: J
authors.lastname: Yundt-Pacheco
authors.affiliation: Bio-Rad Quality System Division, Plano, TX;
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Kuchipudi
authors.affiliation: Bio-Rad Quality System Division, Plano, TX;
authors.forename: Curtis A
authors.initials: CA
authors.lastname: Parvin
authors.affiliation: Emory University School of Medicine, Atlanta, GA.
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Rhea
authors.affiliation: Emory University School of Medicine, Atlanta, GA. rjmolin@emory.edu.
authors.forename: Ross
authors.initials: R
authors.lastname: Molinaro
mesh_terms: D006442:Glycated Hemoglobin / Q000032:analysis* / Q000592:standards; D006801:Humans; D015203:Reproducibility of Results
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human