PB0363 - Development and internal validation of a simple clinical score for the evaluation of deep vein thrombosis

Background: The Wells score comprises subjective elements, which can lead physicians’ reluctance to use the Wells score or use it incorrectly.

Aims: To develop and internally validate an objective and feasible prediction score for the evaluation of patients with suspected DVT with comparable safety to the Wells score.

Methods: Data were retrieved from a previous prospective outcome study (Ri-Schedule; NCT02486445), which included consecutive patients with suspected DVT referred to the Emergency Department at Østfold Hospital Trust, Norway, from 2015 to 2018. Candidate variables were identified by bootstrapping technique and a confirmed DVT diagnosis was used as the outcome variable. Sensitivity, specificity, negative and positive predictive values (NPV and PPV) were estimated and compared to the two-tier Wells score.

Results: Among 1312 patients (median age: 64 years (IQR 52-73), 55% women), 19.9% were diagnosed with DVT. Exploration of 30 variables identified tenderness along the deep veins and previous venous thromboembolism as significant predictors (selection frequency >60% in 1000 bootstrapping samples). DVT was considered as unlikely in 450 patients who had zero items present according to the derived score. Of these 8.0% were diagnosed with DVT as opposed to 8.2% in the DVT unlikely category according to Wells score. Compared to the Wells score, the derived score demonstrated a sensitivity of 86.2 (84.3-88.1) vs 79.7 (77.5-81.9), a specificity of 36.8 (33.7-39.6) vs 55.4 (52.7-58.1), a NPV of 92.0 (90.5-93.5) vs 91.7 (90.2-93.2) and a PPV of 26.1 (23.7-28.5) vs 30.7 (28.2-33.2). When incorporating D-dimer with a cut-off of < 0.5, the derived score had a sensitivity of 98.9 (98.3-99.4), a specificity of 36.7 (34.1-39.3), a NPV of 99.2 (98.8-99.7) and a PPV of 28.0 (25.5-30.4).

Conclusion(s): The derived DVT score, with two objective variables, performed similarly to the Wells score.