title: Hemoglobin A1c as screening for gestational diabetes mellitus in Nordic Caucasian women.
abstract: BACKGROUND
  Gestational diabetes mellitus (GDM) increases the risk for preeclampsia and macrosomia. GDM is conventionally diagnosed by an oral glucose tolerance test (OGTT). Hemoglobin A1c (HbA1c) is a marker for the average glucose level the last 2-3 months. We aimed to study if HbA1c alone or in combination with patient characteristics can be used to screen for GDM and reduce the number of OGTTs, and whether it could predict preeclampsia or birth weight.
  
  
  METHODS
  855 women from a previous study on the effect of exercise on GDM prevalence were eligible, whereof 677 were included. GDM was diagnosed by WHO 1999 criteria (GDM-WHO) and modified IADPSG criteria (GDM-IADPSG), at pregnancy weeks 18-22 and 32-36. HbA1c analyzed at pregnancy weeks 18-22 and 32-36, variables from patient history and clinical examination were considered for logistic regression models. The diagnostic accuracy was assessed by ROC curve analysis.
  
  
  RESULTS
  Accumulated GDM prevalence was 6.7 % by WHO and 7.2 % by modified IADPSG criteria. Nearly a third could potentially have avoided an OGTT by using HbA1c to exclude GDM-IADPSG with a sensitivity of 88 % at week 18-22 and 97 % at week 32-36. Further, 16 % could have avoided an OGTT with a sensitivity of 96 % using HbA1c at week 18-22 to exclude GDM-IADPSG throughout pregnancy. HbA1c was not accurate at diagnosing GDM-IADPSG, and it was inaccurate at screening for GDM-WHO at any time point. Adding other predictors did not increase the number of potentially avoidable OGTTs significantly. HbA1c was not significantly associated with preeclampsia or birth weight.
  
  
  CONCLUSIONS
  HbA1c could potentially reduce the number of OGTTs.
authors.affiliation: Department of Clinical Chemistry, Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway ; Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Ingrid Hov
authors.initials: IH
authors.lastname: Odsæter
authors.affiliation: Department of Clinical Chemistry, Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway.
authors.forename: Arne
authors.initials: A
authors.lastname: Åsberg
authors.affiliation: Department of Obstetrics and Gynecology, Women's Clinic, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway ; Department of Laboratory Medicine, Children's and Women's Health, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Eszter
authors.initials: E
authors.lastname: Vanky
authors.affiliation: Department of Clinical Services, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway ; Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Siv
authors.initials: S
authors.lastname: Mørkved
authors.affiliation: Department of Clinical Services, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway ; Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Signe Nilssen
authors.initials: SN
authors.lastname: Stafne
authors.affiliation: Department of Laboratory Medicine, Children's and Women's Health, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Kjell Åsmund
authors.initials: KÅ
authors.lastname: Salvesen
authors.affiliation: Department of Endocrinology, Clinic of Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway ; Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Sven Magnus
authors.initials: SM
authors.lastname: Carlsen
keywords: Birth weight; Gestational diabetes mellitus; HbA1c; Preeclampsia; Screening