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Aspirin following anticoagulation therapy prevents recurrent VTE (ASPIRE)

Clinical Question:
Does aspirin prevent recurrent venous thrombembolism in patients who have completed an initial course of anticoagulation?

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

Brighton TA, Eikelboom JW, Mann K, et al, for the ASPIRE Investigators. Low-dose aspirin for preventing recurrent venous thromboembolism. N Engl J Med 2012 Nov 4 [Epub ahead of print].  [PMID:23121403]

Study Design:
Randomized controlled trial (double-blinded)



Outpatient (any)

Following a protocol identical to that of the WARFASA trial (Daily POEM 7-13-12), these investigators recruited 822 patients who had completed anticoagulation therapy for an initial, unprovoked VTE. Each patient received either aspirin 100 mg daily or placebo. Patients had a mean age of 54 years and the majority of each group had received anticoagulation for 6 to 12 months prior to 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 infarctions, stroke, or cardiovascular death (5.2% per year 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 that of the WARFASA trial. The combined results showed that daily low-dose aspirin, as compared with placebo, reduced both the risk of recurrent VTE (NNT= 19; hazard ratio [HR] = 0.68; 95% CI, 0.51-0.90; P = .007) and the risk of major vascular events (NNT= 16; HR = 0.66; 95% CI, 0.51-0.86; P = .002) without increasing bleeding.


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