title: Hemoglobin A1c assay variations and implications for diabetes screening in obese youth.
abstract: BACKGROUND
  Standardization of the hemoglobin A1c (A1c) assay has led to its increasing utilization as a screening tool for the diagnosis of prediabetes and type 2 diabetes in youth. However, significant A1c assay variability remains and has implications for clinical management.
  
  
  OBJECTIVE
  To describe our center's experiences with A1c results in youth and to evaluate inter-method differences and their clinical implications.
  
  
  METHODS
  Seventy-five youth (aged 10-18 yr old), body mass index (BMI) ≥85th‰ participated.
  
  
  METHODS
  Seventy-two participants had two A1c values performed on the same sample, one via immunoassay (DCA Vantage Analyzer, A1c1 ) and the other via high performance liquid chromatography (Bio-Rad Variant II, A1c2 ). Nineteen had A1c run on two immunoassay devices (A1c1 and Dimensions Vista, A1c3 ).
  
  
  RESULTS
  Mean age of participants was 13.9 years, BMI% 97.89%, 33% male, 16% white, 21% black, and 61% Hispanic (H). Mean A1c1 was 5.68% ± 0.38 vs. a mean A1c2 of 5.73% ± 0.39, p = 0.049. Concordance in diabetes status between methods was achieved in 79% of subjects. Nineteen subjects with A1c3 results had testing performed an average of 22 ± 9 days prior to A1c1 . Mean A1c3 was 6.24% ± 0.4, compared to a mean A1c1 of 5.74% ± 0.31, (p < 0.0001). A1c1 was on average systematically -0.5 ± 0.28 lower compared to A1c3 . There was poor agreement in diabetes classification between A1c1 and A1c3 , with a concordance in classification between methods of only 36.8%.
  
  
  CONCLUSIONS
  Clinically significant inter-method A1c variability exists that impacts patient classification and treatment recommendations. In the screening of obese youth for diabetes, A1c results should be interpreted with caution.
authors.affiliation: Children's Hospital Colorado, Aurora, CO, USA.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Chan
authors.forename: Kim
authors.initials: K
authors.lastname: McFann
authors.forename: Lindsey
authors.initials: L
authors.lastname: Newnes
authors.forename: Kristen J
authors.initials: KJ
authors.lastname: Nadeau
authors.forename: Philip S
authors.initials: PS
authors.lastname: Zeitler
authors.forename: Megan
authors.initials: M
authors.lastname: Kelsey
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000032:analysis; D015992:Body Mass Index; D002648:Child; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications / Q000175:diagnosis* / Q000208:ethnology; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000592:standards; D015588:Observer Variation; D063766:Pediatric Obesity / Q000097:blood* / Q000150:complications / Q000208:ethnology; D011236:Prediabetic State / Q000097:blood / Q000175:diagnosis / Q000208:ethnology
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
keywords: hemoglobin A1c; obesity; prediabetes; type 2 diabetes