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 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.