title: Diagnostic tests often fail to lead to changes in patient outcomes.
abstract: OBJECTIVE
  To evaluate the effects of diagnostic testing on patient outcomes in a large sample of diagnostic randomized controlled trials (D-RCTs) and to examine whether the effects for patient outcomes correlate with the effects on management and with diagnostic accuracy.
  
  
  METHODS
  We considered D-RCTs that evaluated diagnostic interventions for any condition and reported effectiveness data on one or more patient outcomes. We calculated odds ratios for patient outcomes and outcomes pertaining to the use of further diagnostic and therapeutic interventions and the diagnostic odds ratio (DOR) for the accuracy of experimental tests.
  
  
  RESULTS
  One hundred forty trials (153 comparisons) were eligible. Patient outcomes were significantly improved in 28 comparisons (18%). There was no concordance in significance and direction of effects between the patient outcome and outcomes for use of further diagnostic or therapeutic interventions (weighted κ 0.02 and 0.09, respectively). The effect size for the patient outcome did not correlate with the effect sizes for use of further diagnostic (r = 0.05; P = 0.78) or therapeutic interventions (r = 0.18; P = 0.08) or the experimental intervention DOR in the same trial (r = -0.24; P = 0.51).
  
  
  CONCLUSIONS
  Few tests have well-documented benefits on patient outcomes. Diagnostic performance or the effects on management decisions are not necessarily indicative of patient benefits.
authors.affiliation: Department of Medicine and Mayo School of Graduate Medical Education, College of Medicine, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Konstantinos C
authors.initials: KC
authors.lastname: Siontis
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, University Campus, P.O. Box 1186, 45110 Ioannina, Greece.
authors.forename: George C M
authors.initials: GC
authors.lastname: Siontis
authors.affiliation: Division of Infectious Diseases, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA; Palo Alto Medical Foundation Research Institute, Palo Alto, CA 94301, USA.
authors.forename: Despina G
authors.initials: DG
authors.lastname: Contopoulos-Ioannidis
authors.affiliation: Department of Medicine, Stanford Prevention Research Center, Stanford University School of Medicine, 1265 Welch Rd, MSOB X306, Stanford, CA 94305, USA; Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Statistics, Stanford University School of Humanities and Sciences, Stanford, CA 94305, USA. Electronic address: jioannid@stanford.edu.
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D003955:Diagnostic Tests, Routine; D006801:Humans; D016017:Odds Ratio; D063868:Patient Outcome Assessment; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results
keywords: Diagnostic accuracy; Diagnostic odds ratio; Diagnostic tests; Empirical assessment; Patient outcomes; Randomized controlled trials