Recruiting hard-to-reach subjects: is it worth the effort?

Little information is available on the utility of spending resources to recruit hard-to-reach subjects. In particular, the compliance of such subjects with study protocols and visit schedules has not been documented. We present recruitment data from a two-phase survey of asthma prevalence in which a subset of respondents to a brief screening survey was recruited to attend a 90-min clinic visit. Although 39% of phase I subjects responding to initial contact attempts participated in the second phase of the study, this dropped to 12% among those responding to the sixth contact attempt (a phone follow-up). In studies in which the representatives of the sample is not of paramount importance, we see little benefit in aggressively seeking to recruit hard-to-reach subjects.