title: How high is too high in cutoff levels from 50-g glucose challenge test.
abstract: OBJECTIVE
  To determine the highest 50-g glucose challenge test (GCT) value that indicates no further diagnostic test is needed to confirm a diagnosis of gestational diabetes mellitus (GDM) under the criteria of National Diabetes Data Group (NDDG) or the Carpenter and Coustan (C&C) and fasting glucose thresholds from the International Association of Diabetes and Pregnancy Study Group (IADPSG).
  
  
  METHODS
  We collected the 50-g GCT results from 16,560 pregnancies and identified 2,457 gravidas with positive 50-g GCT (≥130 mg/dL) values who underwent the 100-g glucose tolerance test. We investigated GDM prevalence in pregnancies with positive 50-g GCT according to the respective diagnostic thresholds and determined the 50-g GCT cutoff values with 100% positive predictive value for GDM under each diagnostic threshold.
  
  
  RESULTS
  Twelve point five percent (306/2,457), 20.0% (492/2,457), and 9.6% (235/2,457) met the diagnostic criteria of GDM with the application of NDDG, C&C criteria, and fasting glucose thresholds from IADPSG (≥92 mg/dL), respectively. We also found that the prevalence of GDM increased with increasing 50-g GCT values using each diagnostic criterion. Importantly, we identified that all subjects with a 50-g GCT value ≥223, ≥217, or ≥228 mg/dL can be exclusively diagnosed as having gestational diabetes according to the criteria of NDDG, C&C, and fasting glucose thresholds from IADPSG, respectively.
  
  
  CONCLUSIONS
  We propose that women with a 50-g GCT screening value ≥228 mg/dL can be reliably omitted from further confirmative tests for GDM, such as 100- or 75-g glucose tolerance test.
authors.affiliation: Department of Obstetrics and Gynecology, Kyungpook National University Hospital, Kyungpook National University School of Medicine, Daegu, Korea.
authors.forename: Hyun-Hwa
authors.initials: HH
authors.lastname: Cha
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ji Ye
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Suk-Joo
authors.initials: SJ
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Soo-Young
authors.identifier: 0000-0003-3002-0048
authors.initials: SY
authors.lastname: Oh
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Cheong-Rae
authors.initials: CR
authors.lastname: Roh
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jong-Hwa
authors.initials: JH
authors.lastname: Kim
keywords: Diabetes, gestational; Glucose tolerance test; Positive predictive value