Investment in prolonged thromboprophylaxis with dalteparin improves clinical outcomes after hip replacement

Clinical guidelines recommend the use of extended out-of-hospital thromboprophylaxis in patients who have had major arthroplasty. However, the cost-effectiveness of prolonging pharmacological thromboprophylaxis into the out-of-hospital phase following hip replacement surgery remains the subject of considerable debate. This debate centers on the clinical relevance of the 'surrogate' venographic endpoints that have been used in most clinical trials and used to generate some of the cost analyses of thromboprophylaxis. The objective of this study was to estimate, from the payer perspective, the direct medical costs of prolonging the duration of thromboprophylaxis with dalteparin from 1 week to 28-35 days in patients undergoing hip replacement, and to compare these to the costs associated with using 'standard' in-hospital thromboprophylaxis with low-molecular-weight heparin (LMWH) or warfarin. To derive 'best' estimates for rates of clinically and economically relevant thromboembolism associated with hip replacement surgery (i.e. those that would in reality incur management costs), we used data on the prevalence of both symptomatic and asymptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE). These estimates were used in conjunction with diagnostic-related groups (DRG) reimbursement rates and a dalteparin cost model, which assumed home-based self-administration for prolonged thromboprophylaxis, to calculate overall direct medical costs of prolonged vs. in-hospital thromboprophylaxis. The management costs of the strategies evaluated were, to the nearest 1000 Euros: 465 000 Euros for in-hospital prophylaxis with LMWH; 339 000 Euros for in-hospital prophylaxis with warfarin; and 368 000 Euros for prolonged prophylaxis with dalteparin. For every 1000 patients treated, prolonging thromboprophylaxis with dalteparin from 1 to 4-5 weeks will avoid 30 clinical DVTs and 18 PEs at a saving of 2000 Euros per clinical event. Compared with in-hospital warfarin, prolonged thromboprophylaxis with dalteparin will avoid 28 DVTs and four PEs at an incremental cost-effectiveness ratio of 900 Euros per clinical event avoided. We consider that investment in prolonged thromboprophylaxis with dalteparin is justified for the improvement in clinical outcomes produced.