title: External quality assessment of HbA1c and its effect on comparison between Swedish pediatric diabetes clinics. Experiences from the Swedish pediatric diabetes quality register (Swediabkids) and Equalis.
abstract: BACKGROUND
  To explore to what extent measurement error can explain the variation of mean patient HbA(1c) between clinics.
  
  
  METHODS
  For each year 2005-2010 data from 5380-6985 children, age <18 years, in 35-43 Swedish pediatric clinics was analyzed. Each year 13,000-19,000 HbA(1c) analyses were evaluated. Year mean HbA(1c) for each patient was calculated for HbA(1c) values when insulin dose was ≥0.5 U/kg. In Sweden HbA(1c) values were during the study period standardized to the Mono S level, HbA(1c)(Mono S)%, but are given also in the international unit HbA(1c)(IFCC), mmol/mol. Performance of locally measured HbA(1c) is monitored by Equalis through monthly external quality assessment (EQA) schemes.
  
  
  RESULTS
  The yearly mean bias term for each clinic varied from -0.54 to 0.41 HbA(1c)(Mono S)%. The bias between clinic HbA(1c) and target value improved during the 6 years and the mean bias was for 79%-88% of clinics within the recommended level ±0.14 HbA(1c)% the last 2 years. Inter-clinic mean HbA(1c) had a wide interquartile range, 0.30-0.43 HbA(1c)(Mono S)% [3.2-4.5 HbA(1c)(IFCC)mmol/mol].
  
  
  CONCLUSIONS
  Regular participation in EQA schemes is necessary when comparing HbA(1c) values. The measurement error decreased during the 6-year period and explained from 28% to <10% of the inter-clinic variation in year mean clinic HbA(1c).
authors.forename: Bengt
authors.initials: B
authors.lastname: Lindblad
authors.forename: Gunnar
authors.initials: G
authors.lastname: Nordin
mesh_terms: D000293:Adolescent; D015982:Bias; D001786:Blood Glucose / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D002845:Chromatography / Q000379:methods / Q000592:standards*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007223:Infant; D007328:Insulin / Q000097:blood; D008297:Male; D011786:Quality Control; D012042:Registries; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013548:Sweden
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007328:Insulin; C517652:hemoglobin A1c protein, human