Meta regression analysis to indirectly compare dalteparin to enoxaparin for the prevention of venous thromboembolic events following total hip replacement

BACKGROUND Patients undergoing elective total hip replacement (THR) surgery are at an increased risk for venous thromboembolic events (VTEs). Dalteparin and enoxaparin are recommended as thromboprophylaxis for at least 10 days in these patients. Even though both agents have proven clinical effectiveness through placebo controlled studies, there have been no head to head trials to assess comparative effectiveness. Indirect statistical techniques were used to compare safety and efficacy between dalteparin and enoxaparin following THR surgery. METHODS A literature search was conducted from January 1980 to November 2009 for randomized trials evaluating dalteparin or enoxaparin prophylaxis in THR patients. In trials where a common control was used (e.g. placebo), indirect statistical comparisons between dalteparin and enoxaparin were performed using meta regression analysis with active drug as the primary independent variable. RESULTS A total of nine placebo controlled enoxaparin (n = 5) and dalteparin (n = 4) trials met the inclusion criteria. THR patients treated with enoxaparin or dalteparin had a 50% VTE risk reduction compared to the placebo control (RR = 0.50, p < 0.001). This benefit was achieved without a significant increase in the risk for major bleeds (RR = 1.19, p = 0.76), heparin induced thrombocytopenia (HIT) (RR = 1.13, p = 0.83) or death (RR = 0.72, p = 0.59). The indirect comparison was not able to find significant differences between enoxaparin and dalteparin in terms of VTEs (p = 0.36), major bleeds (p = 0.45), HIT (p = 0.48) and death (p = 0.86). CONCLUSIONS The findings suggested comparable safety and efficacy between dalteparin and enoxaparin in TKR patients. Therefore, treatment decisions should be based on other considerations, such as patient or physician preference, ease of administration and cost.