Deep vein thrombosis (DVT) is a difficult to diagnostic disease. The aim of this study was to determine the utility and accuracy of a risk stratification questionnaire and a diagnostic strategy, which were applied to patients with suspected DVT on lower extremities in an emergency department. A prospective cohort study was performed in 569 outpatients with clinical suspected DVT during 14 months. The applied questionnaire stratified patients into three pre-test probability categories. Items included signs, symptoms, risk factors and potential alternative diagnosis, which were based on a modified Wells clinical model. DVT was diagnosed by the combined use of clinical model, compression ultrasonography (CUS) and follow-up CUS one week later in those moderate-high risk patients with an initial normal test. These patients were followed over three months for the development of venous thromboembolic complications. Two hundred three (35.7%) patients were classified as having a low, 186 (32.7%) moderate and 180 (31.6%) high clinical probability. Overall, DVT was diagnosed in 153 patients (26%; CI95%, 23.2-30.7%): 144 (96%) at the initial CUS, 6 (3.5%) at the second testing and 3 over the 3-month follow-up period. 22 patients had a low pretest probability (11%; CI95%, 7-16%), 43 (23%; CI95%, 17-30%) moderate, and 88 (49%; CI95%, 41-56%) high pretest probability. The difference in the prevalence of DVP among risk categories was significant (p < 0.00001). When the high and moderate groups were joined, the model had a 86% sensitivity, a 90% negative predictive value and a 43% specificity for diagnosis of DVT. The clinical model used in this study is accurate and feasible, though it is not enough to take clinical decisions. The diagnostic strategic used is effective but not efficient.
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