Recruitment for phase II of the trials of hypertension prevention: Effective strategies and predictors of randomization

Phase II of the Trials of Hypertension Prevention is a multicenter, randamized, controlled trial designed to determine the efficacy of weight loss and reduction of sodium intake for lowering blood pressure and incidence of hypertension among persons with high-normal levels of blood pressure. The 2 × 2 factorial study design includes weight loss alone, restricted sodium intake alone, the combination of weight loss and sodium restriction, and a control group. Nine clinical centers used a variety of recruitment strategies to enroll 2382 participants over 17 months, which exceeded the sample size goal of 2250. Among randomized participants, 21% were minorities and 34% were women. Overall, direct mail generated the most randomized participants (73%), followed by community screening (12%) and media advertisement (11%). Referrals from community health care providers yielded few participants, Prescreening improved overall efficiency and reduced costs. Participants who were more likely to drop out voluntarily during the three-visit screening regimen tended to be younger, single, male, smokers, and less educated.