title: Verification and classification bias interactions in diagnostic test accuracy studies for fine-needle aspiration biopsy.
abstract: BACKGROUND
  Reliable estimates of accuracy are important for any diagnostic test. Diagnostic accuracy studies are subject to unique sources of bias. Verification bias and classification bias are 2 sources of bias that commonly occur in diagnostic accuracy studies. Statistical methods are available to estimate the impact of these sources of bias when they occur alone. The impact of interactions when these types of bias occur together has not been investigated.
  
  
  METHODS
  We developed mathematical relationships to show the combined effect of verification bias and classification bias. A wide range of case scenarios were generated to assess the impact of bias components and interactions on total bias.
  
  
  RESULTS
  Interactions between verification bias and classification bias caused overestimation of sensitivity and underestimation of specificity. Interactions had more effect on sensitivity than specificity. Sensitivity was overestimated by at least 7% in approximately 6% of the tested scenarios. Specificity was underestimated by at least 7% in less than 0.1% of the scenarios.
  
  
  CONCLUSIONS
  Interactions between verification bias and classification bias create distortions in accuracy estimates that are greater than would be predicted from each source of bias acting independently.
authors.affiliation: Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Schmidt
authors.forename: Brandon S
authors.initials: BS
authors.lastname: Walker
authors.forename: Michael B
authors.initials: MB
authors.lastname: Cohen
mesh_terms: D015982:Bias; D044963:Biopsy, Fine-Needle; D003955:Diagnostic Tests, Routine / Q000592:standards*; D015340:Epidemiologic Research Design; D019317:Evidence-Based Medicine; D005500:Follow-Up Studies; D006801:Humans; D015233:Models, Statistical; D009369:Neoplasms / Q000145:classification* / Q000175:diagnosis* / Q000453:epidemiology; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology
keywords: classification bias; diagnostic accuracy; fine-needle biopsy; interactions; verification bias