title: Generating pre-test probabilities: a neglected area in clinical decision making.
abstract: OBJECTIVE
  To assess the accuracy and variability of clinicians' estimates of pre-test probability for three common clinical scenarios.
  
  
  METHODS
  Postal questionnaire survey conducted between April and October 2001 eliciting pre-test probability estimates from scenarios for risk of ischaemic heart disease (IHD), deep vein thrombosis (DVT), and stroke.
  
  
  METHODS
  Physicians and general practitioners randomly drawn from College membership lists for New South Wales and north-west England.
  
  
  METHODS
  Agreement with the "correct" estimate (being within 10, 20, 30, or > 30 percentage points of the "correct" estimate derived from validated clinical-decision rules); variability in estimates (median and interquartile ranges of estimates); and association of demographic, practice, or educational factors with accuracy (using linear regression analysis).
  
  
  RESULTS
  819 doctors participated: 310 GPs and 288 physicians in Australia, and 106 GPs and 115 physicians in the UK. Accuracy varied from about 55% of respondents being within 20% of the "correct" risk estimate for the IHD and stroke scenarios to 6.7% for the DVT scenario. Although median estimates varied between the UK and Australian participants, both were similar in accuracy and showed a similarly wide spread of estimates. No demographic, practice, or educational variables substantially predicted accuracy.
  
  
  CONCLUSIONS
  Experienced clinicians, in response to the same clinical scenarios, gave a wide range of estimates for pre-test probability. The development and dissemination of clinical decision rules is needed to support decision making by practising clinicians.
authors.affiliation: Centre for Clinical Epidemiology and Biostatistics, Level 3, David Maddison Building, University of Newcastle, Newcastle, NSW 2300, Australia.
authors.forename: John R
authors.initials: JR
authors.lastname: Attia
authors.forename: Balakrishnan R
authors.initials: BR
authors.lastname: Nair
authors.forename: David W
authors.initials: DW
authors.lastname: Sibbritt
authors.forename: Ben D
authors.initials: BD
authors.lastname: Ewald
authors.forename: Neil S
authors.initials: NS
authors.lastname: Paget
authors.forename: Rod F
authors.initials: RF
authors.lastname: Wellard
authors.forename: Lesley
authors.initials: L
authors.lastname: Patterson
authors.forename: Richard F
authors.initials: RF
authors.lastname: Heller
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia; D002983:Clinical Competence; D003327:Coronary Disease / Q000175:diagnosis; D003657:Decision Making; D003933:Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011336:Probability; D018570:Risk Assessment; D020521:Stroke / Q000175:diagnosis; D011795:Surveys and Questionnaires; D006113:United Kingdom; D020246:Venous Thrombosis / Q000175:diagnosis