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Accuracy of the Wells Rule in diagnosing deep vein thrombosis in primary health care.

AIM
A clinical decision rule to aid in the diagnosis of deep vein thrombosis (DVT) was derived by Wells and has been validated in several secondary care settings. It is now used to reduce unnecessary radiological examinations. The aim of this study was to assess the accuracy of the Wells Rule in New Zealand primary health care.


METHOD
Validation study of the Wells clinical decision rule for DVT in primary health care, using ultrasound as the comparator. Participants included patients with symptoms of DVT from 410 general practitioners in Auckland between 1 October 2004 and 30 September 2005. Sensitivity, specificity, and likelihood ratios were calculated.


RESULTS
432 patients were assessed over 12 months, of whom 327 were eligible to participate. Mean age was 65.5 years (SD 16.1) and 203 (62%) were women. DVT was confirmed in 12% (39/327). Sensitivity was 82% (95% confidence interval [CI]: 67.3-91.0) and specificity 22.5% (CI: 18.1-27.7). Likelihood ratio for a positive test was 1.06 (CI: 0.90-1.24) and for a negative test 0.80 (CI: 0.39-1.61).


CONCLUSION
The Wells Rule used alone had only moderate sensitivity and poor specificity and likelihood ratios, so has limited use in the diagnosis of DVT in primary care.