title: Multivariable adjustments counteract spectrum and test review bias in accuracy studies.
abstract: OBJECTIVE
  The STAndards for Reporting studies of Diagnostic accuracy (STARD) for investigators and editors and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) for reviewers and readers offer guidelines for the quality and reporting of test accuracy studies. These guidelines address and propose some solutions to two major threats to validity: spectrum bias and test review bias.
  
  
  METHODS
  Using a clinical example, we demonstrate that these solutions fail and propose an alternative solution that concomitantly addresses both sources of bias. We also derive formulas that prove the generality of our arguments.
  
  
  RESULTS
  A logical extension of our ideas is to extend STARD item 23 by adding a requirement for multivariable statistical adjustment using information collected in QUADAS items 1, 2, and 12 and STARD items 3-5, 11, 15, and 18.
  
  
  CONCLUSIONS
  We recommend reporting not only variation of diagnostic accuracy across subgroups (STARD item 23) but also the effects of the multivariable adjustments on test performance. We also suggest that the QUADAS be supplemented by an item addressing the appropriateness of statistical methods, in particular whether multivariable adjustments have been included in the analysis.
authors.affiliation: Horten Center, University of Zurich, Bolleystrasse 40, CH-8091 Zurich, Switzerland. lucas.bachmann@usz.ch
authors.forename: Lucas M
authors.initials: LM
authors.lastname: Bachmann
authors.forename: Gerben
authors.initials: G
authors.lastname: ter Riet
authors.forename: Wim E J
authors.initials: WE
authors.lastname: Weber
authors.forename: Alfons G H
authors.initials: AG
authors.lastname: Kessels
mesh_terms: D019937:Diagnostic Techniques and Procedures / Q000592:standards*; D016017:Odds Ratio; D017410:Practice Guidelines as Topic; D012107:Research Design; D015983:Selection Bias