Venous Thrombosis Risk after Arthroscopy of the Knee: Derivation and Validation of the L-TRiP(ascopy) Score.

Patients at high risk for venous thrombosis (VT) following knee arthroscopy could potentially benefit from thromboprophylaxis. We explored the predictive values of environmental, genetic risk factors and levels of coagulation markers to integrate these into a prediction model. Using a population-based case-control study into the aetiology of VT, we developed a (all variables), (easy to use in clinical practice) and (only environmental risk factors) model. The model was transformed into the Leiden-Thrombosis Risk Prediction (arthroscopy) score []. Model validation was performed both internally and externally in another case-control study. A total of 4,943 cases and 6,294 controls were maintained in the analyses, 107 cases and 26 controls had undergone knee arthroscopy. Twelve predictor variables (8 environmental, 3 haemorheological and 1 genetic) were selected from 52 candidates and incorporated into the model (area under the curve [AUC] of 0.81, 95% confidence interval [CI], 0.76-0.86). The model (9 predictors: environmental factors plus factor VIII activity) reached an AUC of 0.76 (95% CI, 0.64-0.88) and the (()) model an AUC of 0.72 (95% CI, 0.60-0.83). In the internal and external validation, the model reached an AUC of 0.78 (95% CI, 0.52-0.98) and 0.75 (95% CI, 0.42-1.00), respectively, while the other models performed slightly less well.