title: The performance of the screening test for gestational diabetes in twin versus singleton pregnancies.
abstract: OBJECTIVE
  To compare the performance of the 50 g glucose challenge test (GCT) and the 100 g oral glucose tolerance test (OGTT) in twin versus singleton pregnancies.
  
  
  METHODS
  A retrospective study of all women who underwent a GCT (24-28 weeks) and delivered in a single tertiary medical center (2001-2012). The performance of the GCT and the OGTT tests were compared between twin and singleton pregnancies.
  
  
  RESULTS
  The results of the GCT were available for 14 797 women, of whom 14 268 were singleton and 529 were twin pregnancies. Women in the twins group were characterized by a higher mean GCT result (104.7 ± 28 versus 98.5 ± 25, p < 0.001), a higher rate of GCT > 130 mg/dl (20.2% versus 11.8%, p < 0.001) or GCT >140 mg/dl (13.8% versus 9.6%, p = 0.001). The positive prediction value (PPV) for a GCT >140 mg/dl was significantly lower in the twins group for the prediction of either ≥1 abnormal values (21.1% versus 33.8%, p = 0.03) or ≥2 abnormal values (12.7% versus 23.0%, p = 0.04) in the OGTT. Twin pregnancy was independently associated with an increased risk for a GCT result >130 mg/dl [odds ratio (OR) = 2.2, 95% confidence interval (CI) 1.7-2.7] or >140 mg/dl (OR = 1.9, 95% CI 1.5-2.5) even after adjustment for maternal age, parity and fetal sex.
  
  
  CONCLUSIONS
  The 50 g GCT appears to be associated with a higher false positive rate and a lower positive predictive value in twin compared with singleton pregnancies.
authors.affiliation: Department of Obstetrics and Gynecology, Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University , Tel Aviv , Israel.
authors.forename: Yariv
authors.initials: Y
authors.lastname: Yogev
authors.forename: Michal
authors.initials: M
authors.lastname: Eisner
authors.forename: Liran
authors.initials: L
authors.lastname: Hiersch
authors.forename: Moshe
authors.initials: M
authors.lastname: Hod
authors.forename: Arnon
authors.initials: A
authors.lastname: Wiznitzer
authors.forename: Nir
authors.initials: N
authors.lastname: Melamed
mesh_terms: D000328:Adult; D016640:Diabetes, Gestational / Q000097:blood / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D005947:Glucose / Q000008:administration & dosage; D005951:Glucose Tolerance Test / Q000379:methods*; D006801:Humans; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011247:Pregnancy; D059285:Pregnancy, Twin / Q000097:blood*; D012189:Retrospective Studies; D013549:Sweetening Agents / Q000008:administration & dosage
chemical_list: D013549:Sweetening Agents; D005947:Glucose