title: Can prevalence expectations drive radiologists' behavior?
abstract: OBJECTIVE
  To measure the effect of explicit prevalence expectation on the performance of experienced radiologists during image interpretation of pulmonary lesions on chest radiographs.
  
  
  METHODS
  Each of 22 experienced radiologists was allocated to one of three groups to interpret a set of 30 (15 abnormal) posteroanterior chest images on two occasions to decide if pulmonary lesions were present. Before each viewing, the radiologists were told that the images contained a specific number of abnormal images: group 1, 9 versus 15; group 2, 22 versus 15; and group 3, not told versus 15, respectively. Eye position metrics and receiver operating characteristics confidence ratings were compared for normal and abnormal images. An analysis of false-positive and false-negative decisions was also performed.
  
  
  RESULTS
  For normal images, at higher prevalence expectation, significant increases were noted for duration of image scrutiny (group 1: P = .0004; group 2: P = .007; and group 3: P = .003) and number of fixations per image (group 1: P = .0006; group 2: P = .0004; and group 3: P = .0001). Also for normal images, group 1 demonstrated a significant increase (P = .038) in average confidence ratings when prevalence expectation increased. For abnormal images, at higher prevalence expectation, significant increases were noted for duration of image scrutiny in group 1 (P = .005) and number of fixations per image in group 1 (P = .01) and group 2 (P = .003).
  
  
  CONCLUSIONS
  Confidence ratings and visual search of the expert radiologists appear to be affected by changing prevalence expectations. The impact of prevalence expectation appears to be more apparent for normal images.
authors.affiliation: Medical Imaging Optimisation and Perception Group (MIOPeG), Discipline of Medical Radiation Sciences, Faculty of Health Sciences, The University of Sydney, Cumberland Campus, East St, PO Box 170, Lidcombe, New South Wales 1825, Australia. Electronic address: warren.reed@sydney.edu.au.
authors.forename: Warren M
authors.initials: WM
authors.lastname: Reed
authors.affiliation: Medical Imaging Optimisation and Perception Group (MIOPeG), Discipline of Medical Radiation Sciences, Faculty of Health Sciences, The University of Sydney, Cumberland Campus, East St, PO Box 170, Lidcombe, New South Wales 1825, Australia.
authors.forename: Suet Ling Candice
authors.initials: SL
authors.lastname: Chow
authors.affiliation: Medical Imaging Optimisation and Perception Group (MIOPeG), Discipline of Medical Radiation Sciences, Faculty of Health Sciences, The University of Sydney, Cumberland Campus, East St, PO Box 170, Lidcombe, New South Wales 1825, Australia.
authors.forename: Lay Ee
authors.initials: LE
authors.lastname: Chew
authors.affiliation: Medical Imaging Optimisation and Perception Group (MIOPeG), Discipline of Medical Radiation Sciences, Faculty of Health Sciences, The University of Sydney, Cumberland Campus, East St, PO Box 170, Lidcombe, New South Wales 1825, Australia.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Brennan
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological; D001291:Attitude of Health Personnel; D002983:Clinical Competence; D003951:Diagnostic Errors / Q000517:prevention & control / Q000523:psychology*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000523:psychology; D008297:Male; D008875:Middle Aged; D009517:New South Wales; D015588:Observer Variation; D010820:Physicians / Q000523:psychology; D010818:Practice Patterns, Physicians'; D015995:Prevalence; D013902:Radiography, Thoracic / Q000523:psychology*; D011871:Radiology; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000523:psychology*
keywords: Thoracic imaging; observer performance; visual search