Clinical Question

Does aspirin prevent recurrent venous thromboembolism (VTE) in patients who have completed an initial course of anticoagulation therapy?

Bottom Line

Although this ASPIRE study was underpowered to detect a difference in the primary outcome, when the results were combined with those of the WARFASA trial, the data show that daily low-dose aspirin prevents recurrent VTE as well as major vascular events without increasing bleeding in patients who have completed anticoagulation therapy for an initial, unprovoked VTE. (Level of Evidence = 1b)

Synopsis

Following a protocol identical to that of the WARFASA trial, investigators recruited 822 patients who had completed anticoagulation therapy for an initial, unprovoked VTE. Each patient received 100 mg of aspirin daily or placebo. Patients were a mean age of 54 years, and the majority of each group had received anticoagulation for six to 12 months before randomization into the study. After a median follow-up of 37 months, there was no significant difference detected between the groups for the primary outcome of recurrent VTE. However, this study was underpowered to detect such a difference if it truly exists. Patients in the aspirin group had a lower rate of major vascular events, defined as the composite of VTE, myocardial infarction, stroke, or cardiovascular death (5.2% vs. 8% per year; number needed to treat [NNT] = 36; P = .01). In addition, there was no significant increase in bleeding events in the aspirin group. Because of slow recruitment and lack of power, the investigators decided a priori to combine the data of this study with those of the WARFASA trial. The combined results showed that daily low-dose aspirin, as compared with placebo, reduced the risk of recurrent VTE (NNT = 19; hazard ratio = 0.68; 95% confidence interval, 0.51 to 0.90; P = .007) as well as the risk of major vascular events (NNT = 16; hazard ratio = 0.66; 95% confidence interval, 0.51 to 0.86; P = .002) without increasing bleeding.

Reference

BrightonTAEikelboomJWMannKet alASPIRE Investigators. Low-dose aspirin for preventing recurrent venous thromboembolism. N Engl J Med.2012; 367( 21): 1979– 1987

Study design: Randomized controlled trial (double-blinded)

Funding source: Government

Allocation: Concealed

Setting: Outpatient (any)