title: The discordance between HbA1c and glucose tolerance testing for the postpartum exclusion of diabetes following gestational diabetes.
abstract: OBJECTIVE
  To assess the concordance between the HbA1c and the oral glucose tolerance test (OGTT) for the diagnosis of diabetes and prediabetes following gestational diabetes (GDM) in an ethnically diverse population.
  
  
  METHODS
  Women with GDM underwent a concurrent OGTT and HbA1c test 6-12 weeks postpartum.
  
  
  RESULTS
  There were 114 women with GDM who had a 75 g 2-h OGTT and HbA1c at 9.0 ± 3.2 weeks postpartum. Five subjects had diabetes using OGTT criteria, and 4 by HbA1c criteria. No subjects had diabetes on both criteria. The overall concordance between the OGTT and HbA1c for the diagnosis of diabetes, prediabetes, or normal glucose tolerance was only 54% (κ coefficient 0.058, p=0.41). Gravidity, the 2-h glucose level on the OGTT during pregnancy, and the 3rd trimester HbA1c predicted discordance between the postpartum OGTT and HbA1c.
  
  
  CONCLUSIONS
  There is poor concordance between the OGTT and HbA1c for the diagnosis of diabetes and prediabetes following GDM. This reflects that the two tests measure different aspects of dysglycemia. In the post-GDM population, the HbA1c misses cases of diabetes as identified by the OGTT. We recommend that the OGTT be retained for postpartum diabetes testing following GDM.
authors: Centre for Diabetes & Endocrinology Research, Westmead Hospital, Westmead 2145, NSW, Australia; Dept of Diabetes & Endocrinology, Blacktown Hospital, Blacktown 2148, NSW, Australia; University of Sydney, Sydney, NSW, Australia. Electronic address: anna.duke@health.nsw.gov.au.
authors: Anna
authors: A
authors: Duke
authors: Centre for Diabetes & Endocrinology Research, Westmead Hospital, Westmead 2145, NSW, Australia; University of Sydney, Sydney, NSW, Australia.
authors: Constance
authors: C
authors: Yap
authors: Centre for Diabetes & Endocrinology Research, Westmead Hospital, Westmead 2145, NSW, Australia; University of Sydney, Sydney, NSW, Australia.
authors: Rachel
authors: R
authors: Bradbury
authors: Dept of Diabetes & Endocrinology, Blacktown Hospital, Blacktown 2148, NSW, Australia; University of Western Sydney, Sydney, NSW, Australia.
authors: Tien M
authors: TM
authors: Hng
authors: Departments of Medicine and Obstetrics & Gynecology, University of Michigan, Ann Arbor, MI 48109, USA.
authors: Catherine
authors: C
authors: Kim
authors: Centre for Diabetes & Endocrinology Research, Westmead Hospital, Westmead 2145, NSW, Australia.
authors: Anne
authors: A
authors: Wansbrough
authors: Centre for Diabetes & Endocrinology Research, Westmead Hospital, Westmead 2145, NSW, Australia; University of Sydney, Sydney, NSW, Australia.
authors: N Wah
authors: NW
authors: Cheung
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000097:blood*; D016640:Diabetes, Gestational / Q000097:blood* / Q000453:epidemiology; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D049590:Postpartum Period; D011247:Pregnancy; D012189:Retrospective Studies
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
keywords: Diabetes screening; Gestational diabetes; HbA1c; Postpartum oral glucose tolerance test; Postpartum screening