A clinical score was recently proposed to rule out concomitant DVT in patients with a clinical suspicion of SVT. This study aimed to assess the external validity of this score in patients from the STEPH study. We performed a post-hoc analysis of data from the STEPH study. The STEPH study was a prospective multicenter community-based study conducted during a 1-year period in the resident adult population of the Greater Saint-Etienne urban area (France). Every patient with a clinical suspicion of SVT underwent a venous compression ultrasonography, to confirm SVT and to assess the presence of a concomitant DVT or not. Odds ratios for concomitant DVT were calculated for each item of the ICARO score. We then computed the score for each patient, and performed a receiver operating characteristic (ROC) curve analysis. In univariate analysis, none of the ICARO items were significantly different given the presence of a concomitant DVT. Given computed scores, 55 patients (45.1%) had a low risk, 17 (13.9%) had an intermediate risk and 50 (41.0%) had a high risk of a concomitant DVT. The area under the ROC curve was 0.386 [95% CI, 0.268-0.504]. When risk levels were dichotomized as low vs intermediate-high risk, the ICARO score had a sensitivity of 36.0%, a specificity of 40.2%, a positive predictive value of 13.4% and a negative predictive value of 70.9%. Our study does not confirm the utility of the ICARO clinical score to rule out concomitant DVT in case of SVT.