title: Assessing variability in results in systematic reviews of diagnostic studies.
abstract: BACKGROUND
  To describe approaches used in systematic reviews of diagnostic test accuracy studies for assessing variability in estimates of accuracy between studies and to provide guidance in this area.
  
  
  METHODS
  Meta-analyses of diagnostic test accuracy studies published between May and September 2012 were systematically identified. Information on how the variability in results was investigated was extracted.
  
  
  RESULTS
  Of the 53 meta-analyses included in the review, most (n=48; 91%) presented variability in diagnostic accuracy estimates visually either through forest plots or ROC plots and the majority (n=40; 75%) presented a test or statistical measure for the variability. Twenty-eight reviews (53%) tested for variability beyond chance using Cochran's Q test and 31 (58%) reviews quantified it with I(2). 7 reviews (13%) presented between-study variance estimates (τ(2)) from random effects models and 3 of these presented a prediction interval or ellipse to facilitate interpretation. Half of all the meta-analyses specified what was considered a significant amount of variability (n=24; 49%).
  
  
  CONCLUSIONS
  Approaches to assessing variability in estimates of accuracy varied widely between diagnostic test accuracy reviews and there is room for improvement. We provide initial guidance, complemented by an overview of the currently available approaches.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center, Universiteitsweg 100, Utrecht, 3584 CG, The Netherlands. c.naaktgeboren@umcutrecht.nl.
authors.forename: Christiana A
authors.initials: CA
authors.lastname: Naaktgeboren
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands.|Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
authors.forename: Eleanor A
authors.initials: EA
authors.lastname: Ochodo
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands.|Dutch Cochrane Centre, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Wynanda A
authors.initials: WA
authors.lastname: Van Enst
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center, Universiteitsweg 100, Utrecht, 3584 CG, The Netherlands.
authors.forename: Joris A H
authors.initials: JAH
authors.lastname: de Groot
authors.affiliation: Dutch Cochrane Centre, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Lotty
authors.initials: L
authors.lastname: Hooft
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands.|Dutch Cochrane Centre, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Mariska M G
authors.initials: MMG
authors.lastname: Leeflang
authors.affiliation: Dutch Cochrane Centre, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Bossuyt
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center, Universiteitsweg 100, Utrecht, 3584 CG, The Netherlands.
authors.forename: Karel G M
authors.initials: KGM
authors.lastname: Moons
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center, Universiteitsweg 100, Utrecht, 3584 CG, The Netherlands.
authors.forename: Johannes B
authors.initials: JB
authors.lastname: Reitsma
mesh_terms: D000704:Analysis of Variance; D003955:Diagnostic Tests, Routine / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data*; D006801:Humans; D015201:Meta-Analysis as Topic; D011642:Publications / Q000592:standards / Q000706:statistics & numerical data; D012372:ROC Curve; D015203:Reproducibility of Results; D012196:Review Literature as Topic