Preliminary validation of clinical assessment for deep vein thrombosis in orthopaedic outpatients

The purpose of our study was to determine if a previously published clinical decision rule designed to estimate the probability of proximal deep vein thrombosis in outpatients is valid when applied exclusively to outpatients with musculoskeletal disorders. We also sought to determine whether probability estimates differed for patients with or without trauma, fracture, or recent orthopaedic surgery. Data collected from outpatients with surgical and nonsurgical musculoskeletal disorders (n = 464) were extracted from the datasets of three previously published studies done on heterogeneous groups of patients (n = 3424). Followup for all patients was 3 months. Testing of all patients for thromboembolic disease was done using validated diagnostic procedures. Probability estimates for orthopaedic outpatients were consistent with estimates from published studies. The proportion of patients who had venous thromboembolism was 5.6% (95% confidence interval, 3.5-8.7%) for the low probability group, 14.1% (95% confidence interval, 8.6-22.4%) for the moderate probability group, and 47.4% (95% confidence interval, 35.3-60%) for the high probability group. Validity estimates for patients with and without recent trauma, surgery, or fracture differed, but not dramatically. The validity of the clinical decision rule as applied to outpatients with musculoskeletal disorders was supported. Level of Evidence: Prognostic study, Level II-1 (retrospective study). See the Guidelines for Authors for a complete description of the levels of evidence.