Rationale and design of the Arterial Disease Multiple Intervention Trial (ADMIT) pilot study

Abstract

The primary objectives of the pilot study were to: (1) evaluate the feasibility of recruiting patients with peripheral arterial disease (PAD); (2) measure the efficacy and safety of high-density lipoprotein (HDL)-raising treatment, low-density lipoprotein (LDL)-lowering therapy, antioxidant therapy, antithrombotic therapy, and their combinations; and (3) assess adherence to a complex multiple drug regimen. Secondary objectives included measurement of the effect of the interventions on prespecified biochemical markers, maintenance of therapy masking (in particular with niacin), and measurement of the intervention's impact on functional status and on quality of life. To date, no secondary prevention trial has been conducted specifically among patients with PAD. Intermittent claudication affects about 0.5% to 1.0% of persons aged >35 years. There is a striking increase in incidence of PAD with age, particularly among those aged >50 years in both sexes, although men are twice as likely as women to develop PAD. The Arterial Disease Multiple Intervention Trial was a double-blind randomized pilot trial of 468 participants with documented PAD. A 2 x 2 x 2 factorial design was used to evaluate the effect of 3 interventions. The pilot incorporated several major novel design features: first, the use of a simple noninvasive method (measurement of ankle brachial index) to identify a population with either symptomatic or asymptomatic PAD; and second, a lipid modifying strategy to increase HDL with nicotinic acid in the intervention group while lowering LDL levels equally with an hydroxymethylglutaryl-coenzyme A reductase inhibitor as needed in the intervention and control group. Two other arms, the antioxidant arm (consisting of beta-carotene and vitamins E and C) and the antithrombotic arm (using warfarin) were also added. Adherence to therapy was measured by pill count, and success in treatment was measured by the proportion of values in target range for HDL, LDL, and the international normalized ratio.