title: A capture-recapture analysis demonstrated that randomized controlled trials evaluating the impact of diagnostic tests on patient outcomes are rare.
abstract: OBJECTIVE
  To estimate the number of randomized controlled trials (RCTs) published annually that evaluate the impact of diagnostic tests on patient outcomes to gauge the extent of available randomized evidence assessing the effectiveness of diagnostic tests.
  
  
  METHODS
  Relevant RCTs published in 2004-2007 were identified from electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL). Two search strategies were developed, one using diagnostic methodological terms and one using test names. Potentially relevant RCTs were identified by screening titles and abstracts. Final inclusion decisions were based on full-text review. A random 10% sample of all citations was independently screened by a second reviewer. Capture-recapture methodology was used to estimate the number of relevant RCTs missed by both searches.
  
  
  RESULTS
  One hundred thirty-five relevant RCTs were identified from the 23,888 records retrieved. Interobserver agreement was substantial. Capture-recapture methodology estimated that 148 (95% confidence interval: 140, 160) relevant RCTs were published in the 4-year period, an average of only 37 publications per year.
  
  
  CONCLUSIONS
  RCTs of diagnostic tests that evaluate patient outcomes are rare. Consequently recommendations on the use of diagnostic tests can rarely be made on the basis of randomized comparisons, lower grade evidence frequently being the best available.
authors: Department of Public Health, Epidemiology & Biostatistics, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
authors: Lavinia
authors: L
authors: Ferrante di Ruffano
authors: Clare
authors: C
authors: Davenport
authors: Anne
authors: A
authors: Eisinga
authors: Chris
authors: C
authors: Hyde
authors: Jonathan J
authors: JJ
authors: Deeks
mesh_terms: D003625:Data Collection / Q000379:methods*; D016206:Databases, Bibliographic; D003952:Diagnostic Imaging; D017408:Guidelines as Topic; D006801:Humans; D046650:Medical Subject Headings; D015588:Observer Variation; D017063:Outcome Assessment, Health Care; D011643:Publishing / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic / Q000379:methods / Q000706:statistics & numerical data*