title: Revaluation of biological variation of glycated hemoglobin (HbA(1c)) using an accurately designed protocol and an assay traceable to the IFCC reference system.
abstract: BACKGROUND
  Glycated hemoglobin (HbA(1c)) has a key role for diagnosing diabetes and monitoring glycemic state. As recently reviewed, available data on HbA(1c) biological variation show marked heterogeneity. Here we experimentally revaluated these data using a well designed protocol.
  
  
  METHODS
  We took five EDTA whole blood specimens from 18 apparently healthy subjects on the same day, every two weeks for two months. Samples were stored at -80°C until analysis and assayed in duplicate in a single run by Roche Tina-quant® Gen.2 immunoassay. Data were analyzed by the ANOVA. To assess the assay traceability to the IFCC reference method, we preliminarily carried out a correlation experiment.
  
  
  RESULTS
  The bias (mean±SD) of the Roche immunoassay was 0.3%±0.7%, confirming the traceability of the employed assay. No difference was found in HbA(1c) values between men and women. Within- and between-subject CV were 2.5% and 7.1%, respectively. Derived desirable analytical goals for imprecision, bias, and total error resulted 1.3%, 1.9%, and 3.9%, respectively. HbA(1c) had marked individuality, limiting the use of population-based reference limits for test interpretation. The estimated critical difference was ~10%.
  
  
  CONCLUSIONS
  For the first time we defined biological variation and derived indices for the clinical application of HbA(1c) measurements using an accurately designed protocol and an assay standardized according to the IFCC.
authors.affiliation: Centre for Metrological Traceability in Laboratory Medicine (CIRME), University of Milano, Milano, Italy. federica.braga@studenti.unimi.it
authors.forename: Federica
authors.initials: F
authors.lastname: Braga
authors.forename: Alberto
authors.initials: A
authors.lastname: Dolci
authors.forename: Martina
authors.initials: M
authors.lastname: Montagnana
authors.forename: Franca
authors.initials: F
authors.lastname: Pagani
authors.forename: Renata
authors.initials: R
authors.lastname: Paleari
authors.forename: Gian Cesare
authors.initials: GC
authors.lastname: Guidi
authors.forename: Andrea
authors.initials: A
authors.lastname: Mosca
authors.forename: Mauro
authors.initials: M
authors.lastname: Panteghini
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis; D004492:Edetic Acid; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D012016:Reference Values
chemical_list: D015415:Biomarkers; D004492:Edetic Acid; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human