title: Results of diagnostic accuracy studies are not always validated.
abstract: OBJECTIVE
  Internal validation of a diagnostic test estimates the degree of random error, using the original data of a diagnostic accuracy study. External validation requires a new study in an independent but similar population. Here we describe whether diagnostic research is validated, which technique is used, and to what extent the validation study results differ from the original.
  
  
  METHODS
  All original diagnostic accuracy studies published in 1993 in a predefined set of journals were selected. Validation of these studies was assessed in the original article and in articles published within a period of 10 years, through a literature search and contacting the authors.
  
  
  RESULTS
  None of the original studies reported any form of validation. Validation studies published later could be identified for 7 of the 11 original studies. Test characteristics were difficult to compare. Despite what was generally believed, not every validation study showed results inferior to the original. We found more studies that evaluated the test in a different population than in a similar one.
  
  
  CONCLUSIONS
  Not every diagnostic accuracy study is validated. Diagnostic tests are more often repeated in different populations.
authors.affiliation: Department of General Practice ACHG, Katholieke Universiteit Leuven, Kapucijnenvoer 33, Blok J, 3000 Leuven, Belgium. ann.vandenbruel@med.kuleuven.be
authors.forename: Ann
authors.initials: A
authors.lastname: Van den Bruel
authors.forename: Bert
authors.initials: B
authors.lastname: Aertgeerts
authors.forename: Frank
authors.initials: F
authors.lastname: Buntinx
mesh_terms: D016206:Databases, Bibliographic; D019937:Diagnostic Techniques and Procedures / Q000592:standards*; D006801:Humans; D010506:Periodicals as Topic; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012107:Research Design