Aspirin prevents vascular events in patients with PAD

Clinical Question

Is low-dose aspirin effective in preventing serious vascular events in patients with peripheral arterial disease?

Bottom Line

Low-dose aspirin prevents major vascular events in patients with peripheral arterial disease with a number needed to treat (NNT) of 14 for 2 years. The study was too small to assess whether there is a risk reduction in critical leg ischemia events. Many of these patients have an indication for aspirin based on the presence of established coronary artery disease or diabetes. (LOE = 1b)


Critical Leg Ischaemia Prevention Study (CLIPS) Group; Catalano M, Born G, Peto R. Prevention of serious vascular events by aspirin amongst patient with peripheral arterial disease: randomized, double-blind trial. Journal of Internal Medicine 2007;261:276-284.  [PMID:17305650]

Study Design

Randomized controlled trial (double-blinded)


Industry + foundation




Outpatient (any)


The original plan for this study was to recruit a sample of 2000 patients with peripheral arterial disease. However, this became difficult because of widespread aspirin use for other indications, and recruitment was therefore stopped at 366 patients. A serious vascular event was defined as a fatal or nonfatal myocardial infarction or stroke, or death that could not be ascribed to a nonvascular cause such as cancer. Critical leg ischemia was defined as ischemic pain at rest for more than 2 weeks, with or without ulcers or gangrene, plus ankle and toe blood pressure criteria. Patients were randomized to 4 groups: aspirin 100 mg daily; antioxidant vitamins (vitamin E 600 mg, vitamin C 250 mg, and beta-carotene 20 mg); both; or neither. Diabetic patients were included. Patients were followed up every 3 months for 2 years. There was a significant reduction in major vascular events in the aspirin-treated groups: 7 of 185 versus 20 of 181 (4% vs 11%; P = .02; NNT = 14; 95% CI, 8-53). Critical leg ischemia occurred in 2.7% of aspirin-treated patients versus 4.4% of placebo patients (NS). As in other studies there was no benefit with antioxidant vitamins. Neither treatment was associated with an increase in adverse events in this small study.