Limited ability of the Caprini Score to predict the risk of venous thromboembolism in patients undergoing orthopedic surgeries

PURPOSE : The purpose of this study was to validate the Caprini score in patients undergoing any orthopedic surgery. METHODS : Data from a large population-based case–control study (MEGA study) on the etiology of VTE were used. Cases and controls completed a questionnaire on risk factors for VTE, which information was used to calculate the Caprini score. Odds Ratios (OR) with their 95% Confidence Intervals (95%CI) were calculated. Sensitivity, specificity and positive predictive value (PPV) were also evaluated. The overall discriminative predictive performance was assessed by estimating the Area Under the Curve (AUC) with a Receiver Operating Characteristic. RESULTS: Of 4,721 cases and 5,638 controls, 263 cases and 94 controls had undergone an orthopedic surgery. A total of 20.9% (55/263) cases and 41.5% (39/94) controls were classified in the lowest risk group (Caprini <5 points). Patients with a Caprini score >11 points had about six-fold (OR 6.3, CI 95% 1.7-22.9) increased risk of VTE and patients with a score of 9-10 had a three-fold increased risk (OR 3.5, CI 95% 1.2-10.3), as compared to patients with a Caprini score of 0-2 points. The discriminative performance was moderate with an AUC of 0.64 (CI 95% 0.58-0.71). Using a cut-off >5 points to stratify patients at high risk of VTE, the sensitivity was 79%, the specificity was 41% and the PPV 2.3%. CONCLUSION : The Caprini score is a tool that can assist orthopedic surgeons to classify patients’ risk for post-operative VTE. However, its discriminative predictive performance was estimated to be moderate.