The more a potential trial volunteer learns about the clinical trial process, the less likely he or she is to agree to participate.

That finding stunned Patrina Caldwell, lead author of the report “Strategies for Increasing Recruitment to Randomised Controlled Trials: Systematic Review,” published in a recent issue of PLoS Medicine.

“This was quite surprising,” she said. “This may have to do with people’s fear of research and the unknown. Understanding the process may not necessarily be reassuring. So many people assume doctors know more than they actually know and that doctors know what is best for them. Discovering that actually people don’t know, and we have to do an experiment to find out, can be quite frightening.”

For the study, she and colleagues from the University of Sydney, New South Wales, Australia, culled through MEDLINE, Embase, The Cochrane Library and other reference lists and scrutinized recruitment strategies used in 37 studies in which 18,812 of at least 59,354 people approached agreed to participate in a clinical randomized trial. The recruitment strategies they examined were divided into four groups: novel trial designs, recruiter differences, incentives and provision of trial information.

But Caldwell’s research also showed that understanding more about their health conditions and the impact on them—and perhaps the lack of information that currently exists about the subject—may have a motivating effect on people considering participation in a clinical trial, she said.

Strategies she and her colleagues found improved recruitment included increasing people’s awareness of the health problem being studied, adding a health questionnaire or video about the health condition and offering monetary incentives.

The authors concluded that trial recruitment strategies that focus on increasing potential participants’ awareness of the health problem being studied and its possible effects on their health is likely to increase recruitment to randomized trials.

The study constitutes one of only three such close reviews of the recruitment process. One, conducted in 2002, was released in 2007 and focused on all types of research, not just randomized clinical trials. Another, published in 2006, examined studies conducted from 1996 to 2004. Caldwell—senior lecturer on the discipline of pediatrics and child health at the University of Sydney and staff specialist at the Children’s Hospital at Westmead’s Centre for Kidney Research—says her paper is more far-reaching, having examined studies conducted from 1950 to 2009.

Why isn’t there more research on how clinical trials are conducted? Caldwell says the reason is largely financial.

“There is little funding for research about research,” she said. “Most funders want to find the cure to cancer or some other clinical condition; research about research is generally not terribly interesting to the lay public.”

But that may be changing. “I think research about research is starting to take off,” she added. “Increasingly, with the introduction of evidence-based medicine, researchers and scientists have looked harder at how research is done and are beginning to question research findings rather than just believing the results. This has led researchers to start looking at how we do research, and to think about how to do research better.”

—Suz Redfearn