Table 1.

Recent studies on prevention of recurrent unprovoked VTE by aspirin

Study	Type of trial	Participants of the study and their number	Prior anticoagulant treatment	VTE events
WARFASA50	Double-blinded randomized controlled trial	Patients with previous unprovoked VTE Aspirin group =205 Placebo group =197	At least 6 to 12 months	VTE Aspirin group =28 Placebo group =43 (HR 0.58, 95% Cl: 0.36–0.93, P=0.02)
ASPIRE52	Double-blinded randomized controlled trial	Patients with previous unprovoked VTE Aspirin group =411 Placebo group =411	At least 1.5 to 24 months	VTE Aspirin group =28 Placebo group =43 (HR 0.47, 95% Cl: 0.52–1.05, P=0.09)
INSPIRE56	A prospective combined analysis of the WARFASA and ASPIRE trials	Patients with previous unprovoked VTE 1,225 randomized Aspirin group =616 Placebo group =609	Patients were followed up for at least 2 years in the WARFASA trial and up to 4 years in ASPIRE	VTE Aspirin group =81 Placebo group =112 BABC (HR 0.68, 95% CI: 0.51–0.90, P=0.008) AABC (HR 0.65, 95% CI: 0.49–0.86, P=0.003)
EINSTEIN CHOICE60 (Design of the EINSTEIN CHOICE study)	Double-blinded randomized controlled trial	Patients with previous unprovoked VTE 2,850 patients Rivaroxaban group (10 mg) =950 Rivaroxaban group (20 mg) =950 Aspirin group (l00 mg) =950	At least 6 to 12 months	This trial will be the first study to compare the benefit-to-risk profile of two doses (10 and 20 mg) of an anticoagulant with that of aspirin for extended VTE treatment

Abbreviations: AABC, after adjustment of baseline characteristics; BABC, before adjustment of baseline characteristics; CI, confidence interval; HR, hazard ratio; VTE, venous thromboembolism.