title: An analysis of systematic reviews indicated low incorpororation of results from clinical trial quality assessment.
abstract: OBJECTIVE
  We investigated the frequency of quality assessment of randomized controlled trials within systematic reviews and the incorporation of the quality assessment in the analysis.
  
  
  METHODS
  We included new systematic reviews of at least five trials of therapeutic or preventive interventions that appeared in issue 2, 2003, of the Cochrane Database of Systematic Reviews. All systematic reviews in the 2002 issues of the Annals of Internal Medicine, BMJ, JAMA, and Lancet were identified in Pubmed. All reviews were assessed under unblinded conditions using preprinted extraction forms.
  
  
  RESULTS
  Trial quality was assessed in all Cochrane reviews and most (74%) of the paper reviews. When we excluded 11 paper reviews that were also published as Cochrane review, the percentage remained similar (67%). Fifty percent of all Cochrane reviews and 61% of all paper reviews incorporated the results of the quality assessment in the analysis.
  
  
  CONCLUSIONS
  Half of the reviews did not incorporate the results of the quality assessment in the analysis. Authors, peer-reviewers, and editors should no longer focus exclusively on whether quality assessment has been performed but should also concentrate on incorporation of quality assessments in the analysis of the systematic review.
authors.affiliation: Department of General Internal Medicine, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. craen@lumc.nl
authors.forename: Anton J M
authors.initials: AJ
authors.lastname: de Craen
authors.forename: Huib A A M
authors.initials: HA
authors.lastname: van Vliet
authors.forename: Frans M
authors.initials: FM
authors.lastname: Helmerhorst
mesh_terms: D016206:Databases, Bibliographic / Q000592:standards; D019317:Evidence-Based Medicine / Q000592:standards; D006801:Humans; D011786:Quality Control; D016032:Randomized Controlled Trials as Topic / Q000592:standards*; D012107:Research Design; D012196:Review Literature as Topic