title: Trajectories of HbA1c levels in children and youth with type 1 diabetes.
abstract: OBJECTIVE
  To illustrate the distribution of Hemoglobin A1c (HbA1c) levels according to age and gender among children, adolescents and youth with type 1 diabetes (T1DM).
  
  
  METHODS
  Consecutive HbA1c measurements of 349 patients, aged 2 to 30 years with T1DM were obtained from 1995 through 2010. Measurement from patients diagnosed with celiac disease (n = 20), eating disorders (n = 41) and hemoglobinopathy (n = 1) were excluded. The study sample comprised 4815 measurements of HbA1c from 287 patients. Regression percentiles of HbA1c were calculated as a function of age and gender by the quantile regression method using the SAS procedure QUANTREG.
  
  
  RESULTS
  Crude percentiles of HbA1c as a function of age and gender, and the modeled curves produced using quantile regression showed good concordance. The curves show a decline in HbA1c levels from age 2 to 4 years at each percentile. Thereafter, there is a gradual increase during the prepubertal years with a peak at ages 12 to 14 years. HbA1c levels subsequently decline to the lowest values in the third decade. Curves of females and males followed closely, with females having HbA1c levels about 0.1% (1.1 mmol/mol) higher in the 25th 50th and 75th percentiles.
  
  
  CONCLUSIONS
  We constructed age-specific distribution curves for HbA1c levels for patients with T1DM. These percentiles may be used to demonstrate the individual patient's measurements longitudinally compared with age-matched patients.
authors.affiliation: Maccabi Juvenile Diabetes Center, Raanana, Israel; Pediatric Endocrine and Diabetes Unit, Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel Hashomer, Israel; Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel.
authors.forename: Orit
authors.initials: O
authors.lastname: Pinhas-Hamiel
authors.affiliation: Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel.
authors.forename: Uri
authors.initials: U
authors.lastname: Hamiel
authors.affiliation: The Women and Children's Health Research Unit, Gertner Institute, Tel Hashomer, Israel.
authors.forename: Valentina
authors.initials: V
authors.lastname: Boyko
authors.affiliation: Maccabi Juvenile Diabetes Center, Raanana, Israel.
authors.forename: Chana
authors.initials: C
authors.lastname: Graph-Barel
authors.affiliation: Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel; The Women and Children's Health Research Unit, Gertner Institute, Tel Hashomer, Israel.
authors.forename: Brian
authors.initials: B
authors.lastname: Reichman
authors.affiliation: Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel; The Women and Children's Health Research Unit, Gertner Institute, Tel Hashomer, Israel.
authors.forename: Liat
authors.initials: L
authors.lastname: Lerner-Geva
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism* / Q000592:standards; D006801:Humans; D008297:Male; D012016:Reference Values; D055815:Young Adult
chemical_list: D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human