Recruiting vulnerable populations for research: revisiting the ethical issues.

The successful recruitment of participants is essential to the research process. To increase the rate of subject participation, investigators have to rely on help from health care providers who often serve as gatekeepers to potential research study subjects. These well-meaning professionals may limit subject participation in a study involving vulnerable populations under the guise of protecting these individuals from harm. We describe some of the characteristics of vulnerable populations affecting their recruitment into research studies. We examine the ethical conflicts that occur when health care professionals control access to these subjects during recruitment for research studies. Finally, we discuss the implications for practice and research designed to protect the rights of vulnerable populations participating in research. We identify collaboration and dialogue between researchers, health care providers, and members of the potential subject populations as most important in recruiting sufficient numbers of subjects to ensure the scientific merit of the study.