Recurrent venous thromboembolism (VTE) contributes to morbidity and mortality. Although the adequacy of initial anticoagulation is a determinant of recurrence, little is known about how the type of initial outpatient anticoagulation affects the risk for recurrent VTE.
We used claims from a large, third-party payer (2004–2007) to identify patients treated as outpatients with fondaparinux or enoxaparin, and diagnosed with pulmonary embolism (PE) or deep vein thrombosis (DVT), excluding pregnant patients. We compared rates of 30-day VTE recurrence (PE or DVT) as a function of initial treatment with fondaparinux versus enoxaparin. Bleeding complications represented a secondary endpoint. We adjusted for potential confounders (demographics, healthcare utilization, co-morbid illnesses including cancer, recent surgery, and initial VTE type) through multivariate logistic regression; and used propensity-score (PS) matching to control for treatment choice-associated factors. We matched fondaparinux- to enoxaparin-treated patients in a1:4 ratio.
The study included 31,635 patients receiving fondaparinux (n = 607) or enoxaparin (n = 31,028). Two-thirds of patients presented with a DVT, 16% PE and 16% DVT/PE. Unadjusted recurrence rates were similar between fondaparinux and enoxaparin (4.6% vs. 5.9%, p = 0.18); and the rate of bleeding events was 0.66%. Multivariate analysis indicated that fondaparinux patients were 34% less likely to suffer recurrent VTE (OR: 0.66, 95% CI: 0.45–0.98, p = 0.037) compared with enoxaparin. Other factors independently associated with VTE recurrence included recent surgery and chronic disease severity measured by the Charlson score. In the PS analysis, 569 fondaparinux patients were matched to 2276 enoxaparin patients; VTE recurred less often in the fondaparinux cohort (4.9% vs. 7.6%, p = 0.026); and bleeding rates did not vary based on initial therapy.
VTE patients treated with fondaparinux or enoxaparin as outpatients have similar crude rates of recurrent VTE with low bleeding risk. Adjusted analyses suggest that fondaparinux, (versus enoxaparin) may be associated with a decreased risk for recurrence.
Physicians should be vigilant for VTE recurrence and appreciate that the type of initial outpatient anticoagulation may impact subsequent risk for recurrent thrombosis.
Andrew Shorr, Grant monies (from industry related sources) Astellas, GSK, J and J, Pfizer, Sanofi; Consultant fee, speaker bureau, advisory committee, etc. Astellas, BI, GSK, J and J, Medicines Co. Merck, Pfizer, Sanofi, Theravance; Other This project was supported by GSK; No Product/Research Disclosure Information