Recruiting healthy participants for a large clinical trial

The Lung Health Study (LHS) is a multicenter randomized clinical trial evaluating treatments for the prevention of chronic obstructive pulmonary disease (COPD). Participants are otherwise healthy smokers with borderline abnormal lung function, who are at relatively high risk of developing COPD. LHS recruiting efforts in the city of Winnipeg, Canada, resulted in the screening of 9,062 people (21% of age-eligible smokers) and randomization of 577 participants. Approximately 50% of the screenees were obtained by direct mail with follow-up telephone calls, while another 14% of the screenees were obtained at worksites. Other recruiting methods included use of mass media, passive displays at community events, and interviewer-aided mall recruiting. Screening rates (percent of the total age-eligible population in Winnipeg screened) were inversely related to age, although eligibility rates were directly related to age. Screening rate was inversely related to indicators of socioeconomic status independent of smoking status. However, randomization rates (percent of the age-eligible population which was randomized) were directly related to socioeconomic status, in part because exclusions for medical reasons were also inversely related to socioeconomic status. Eligibility at initial screening was not related to the recruiting method, but the likelihood of randomizing eligible participants was significantly greater at this clinic for those recruited via mass media and workplace screening than for those recruited by direct mail, and significantly less when recruited at community events.