Targeted prophylactic anticoagulation based on the TRiP(cast) score in patients with lower limb immobilisation: a multicentre, stepped wedge, randomised implementation trial

Prophylactic anticoagulation in emergency department patients with lower limb trauma requiring immobilisation is controversial. The Thrombosis Risk Prediction for Patients with Cast Immobilisation—TRiP(cast)—score could identify a large subgroup of patients at low risk of venous thromboembolism for whom prophylactic anticoagulation can be safely withheld. We aimed to prospectively assess the safety of withholding anticoagulation for patients with lower limb trauma at low risk of venous thromboembolism, defined by a TRiP(cast) score of less than 7. CASTING was a stepped-wedge, multicentre, cluster-randomised trial with blinded outcome assessment. 15 emergency departments in France and Belgium were selected and randomly assigned staggered start dates for switching from the control phase (ie, anticoagulation prescription according to the physician's usual practice) to the intervention phase (ie, targeted anticoagulation according to TRiP(cast) score: no prescription if score