Generating pre-test probabilities: a neglected area in clinical decision making

Med J Aust. 2004 May 3;180(9):449-54. doi: 10.5694/j.1326-5377.2004.tb06020.x.


Objective: To assess the accuracy and variability of clinicians' estimates of pre-test probability for three common clinical scenarios.

Design: 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.

Participants and setting: Physicians and general practitioners randomly drawn from College membership lists for New South Wales and north-west England.

Main outcome measures: 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.

MeSH terms

  • Adult
  • Aged
  • Australia
  • Clinical Competence
  • Coronary Disease / diagnosis
  • Decision Making*
  • Diagnosis*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Probability*
  • Risk Assessment
  • Stroke / diagnosis
  • Surveys and Questionnaires
  • United Kingdom
  • Venous Thrombosis / diagnosis