title: Risk factor screening to identify women requiring oral glucose tolerance testing to diagnose gestational diabetes: A systematic review and meta-analysis and analysis of two pregnancy cohorts.
abstract: BACKGROUND
  Easily identifiable risk factors including: obesity and ethnicity at high risk of diabetes are commonly used to indicate which women should be offered the oral glucose tolerance test (OGTT) to diagnose gestational diabetes (GDM). Evidence regarding these risk factors is limited however. We conducted a systematic review (SR) and meta-analysis and individual participant data (IPD) analysis to evaluate the performance of risk factors in identifying women with GDM.
  
  
  METHODS
  We searched MEDLINE, Medline in Process, Embase, Maternity and Infant Care and the Cochrane Central Register of Controlled Trials (CENTRAL) up to August 2016 and conducted additional reference checking. We included observational, cohort, case-control and cross-sectional studies reporting the performance characteristics of risk factors used to identify women at high risk of GDM. We had access to IPD from the Born in Bradford and Atlantic Diabetes in Pregnancy cohorts, all pregnant women in the two cohorts with data on risk factors and OGTT results were included.
  
  
  RESULTS
  Twenty nine published studies with 211,698 women for the SR and a further 14,103 women from two birth cohorts (Born in Bradford and the Atlantic Diabetes in Pregnancy study) for the IPD analysis were included. Six studies assessed the screening performance of guidelines; six examined combinations of risk factors; eight evaluated the number of risk factors and nine examined prediction models or scores. Meta-analysis using data from published studies suggests that irrespective of the method used, risk factors do not identify women with GDM well. Using IPD and combining risk factors to produce the highest sensitivities, results in low specificities (and so higher false positives). Strategies that use the risk factors of age (>25 or >30) and BMI (>25 or 30) perform as well as other strategies with additional risk factors included.
  
  
  CONCLUSIONS
  Risk factor screening methods are poor predictors of which pregnant women will be diagnosed with GDM. A simple approach of offering an OGTT to women 25 years or older and/or with a BMI of 25kg/m2 or more is as good as more complex risk prediction models. Research to identify more accurate (bio)markers is needed. Systematic Review Registration: PROSPERO CRD42013004608.
authors.affiliation: Bradford Institute for Health Research, Bradford Institute for Health Research, Bradford Royal Infirmary, Bradford, United Kingdom.|Department of Health Sciences, University of York, York, United Kingdom.
authors.forename: Diane
authors.identifier: http://orcid.org/0000-0002-5625-761X
authors.initials: D
authors.lastname: Farrar
authors.affiliation: Centre for Reviews and Dissemination, University of York, York, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Simmonds
authors.affiliation: Bradford Institute for Health Research, Bradford Institute for Health Research, Bradford Royal Infirmary, Bradford, United Kingdom.|Leeds Institute of Clinical Trials Research, University of Leeds, Leeds, United Kingdom.
authors.forename: Maria
authors.initials: M
authors.lastname: Bryant
authors.affiliation: MRC Integrative Epidemiology Unit at the University of Bristol, Oakfield House, Oakfield Grove, Bristol, United Kingdom.|School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Debbie A
authors.initials: DA
authors.lastname: Lawlor
authors.affiliation: Galway Diabetes Research Centre (GDRC) and School of Medicine, National University of Ireland, Galway, Republic of Ireland.
authors.forename: Fidelma
authors.initials: F
authors.lastname: Dunne
authors.affiliation: Bradford Women's and Newborn Unit, Bradford, United Kingdom.
authors.forename: Derek
authors.initials: D
authors.lastname: Tuffnell
authors.affiliation: Department of Health Sciences, University of York, York, United Kingdom.
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Sheldon
mesh_terms: D015331:Cohort Studies; D016640:Diabetes, Gestational / Q000175:diagnosis*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D011247:Pregnancy; D012307:Risk Factors