Review: The Wells clinical prediction guide and D-dimer testing predict deep vein thrombosis.

M e t h o d s Data sources: MEDLINE (1990 to 1 July 2004) and relevant references in English and French. Study selection and assessment: Studies were selected if they were prospective trials with ≥ 3-month follow-up, enrolled consecutive outpatients with symptoms and signs suggestive of DVT, used a validated CPG to estimate the clinical probability (low, moderate, and high) of DVT before D-dimer testing or diagnostic imaging, and evaluated proximal DVT. In studies that included D-dimer testing, testing had to be done before other diagnostic tests. Studies of patients with previous DVT that was not adjusted for by the CPG or the reviewers were excluded. 14 studies (n = 8239) met the selection criteria; all evaluated the Wells CPG. 11 studies (n = 5690) incorporated D-dimer testing in the CPG. Quality assessment of individual studies was based on independent, blinded comparison of symptoms or signs with a diagnostic reference standard among patients with suspected DVT. Outcomes: DVT. M a i n r e s u l t s The prevalence of DVT in the low, moderate, and high clinical probability groups was 5.0% (95% CI 4.0 to 8.0), 17% (CI 13 to 23), and 53% (CI 44 to 61), respectively. Meta-analysis showed that the specificity of D-dimer testing (high sensitivity assays, moderate sensitivity assays, and overall) decreased as the clinical probability rose from low to high (overall P < 0.001; P value not reported for high-sensitivity and moderatesensitivity assays, respectively) for predicting DVT, but the sensitivity of D-dimer testing did not differ among the 3 clinical probability groups (Table). C o n c l u s i o n s In patients with suspected deep venous thrombosis (DVT), low clinical probability on the Wells clinical prediction guide combined with negative D-dimer test results rules out DVT. High clinical probability or a positive D-dimer test result requires further ultrasonography testing.