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Generating pre-test probabilities: a neglected area in clinical decision making
John R Attia1, Balakrishnan R Nair, David W Sibbritt
1Centre for Clinical Epidemiology and Biostatistics, Level 3, David Maddison Building, University of Newcastle, Newcastle, NSW 2300, Australia.
Insights
Clinicians showed significant variability in estimating pre-test probability for ischaemic heart disease, deep vein thrombosis, and stroke. This highlights the need for clinical decision rules to support accurate risk assessment in practice.
Area of Science:
- Medical Decision Making
- Clinical Risk Assessment
- Health Services Research
Background:
- Accurate estimation of pre-test probability is crucial for effective clinical decision-making.
- Variability in clinicians' risk assessments can lead to suboptimal patient management.
- Existing clinical decision rules aim to standardize risk stratification.
Purpose of the Study:
- To evaluate the accuracy and consistency of clinicians' pre-test probability estimates.
- To assess clinician accuracy across three common clinical scenarios: ischaemic heart disease (IHD), deep vein thrombosis (DVT), and stroke.
- To identify factors influencing the accuracy of these estimates.
Main Methods:
- A postal questionnaire survey was conducted from April to October 2001.
- Clinicians (physicians and general practitioners) from Australia and the UK estimated pre-test probabilities for IHD, DVT, and stroke scenarios.
- Accuracy was measured against validated clinical-decision rules; variability was assessed using median and interquartile ranges.
Main Results:
- 819 clinicians participated in the survey.
- Accuracy varied widely, with only 6.7% of respondents accurately estimating DVT risk within 20% of the correct value, compared to approximately 55% for IHD and stroke.
- Despite geographical differences, clinicians in Australia and the UK showed similar accuracy and wide variability in their estimates; no demographic or educational factors predicted accuracy.
Conclusions:
- Experienced clinicians exhibit considerable variation in pre-test probability estimates for common conditions.
- There is a clear need for the development and implementation of clinical decision rules to aid practicing clinicians.
- Standardized tools are essential to improve the consistency and accuracy of clinical risk assessment.
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.
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