Does modification to the approach to contacting potential participants improve recruitment to clinical trials?

It is critical that clinical trial researchers ensure efficient and successful patient recruitment. Recruitment is often slower than expected and required sample sizes not obtained within initial funding deadlines. There is little rigorous evidence supporting ways to improve recruitment. We hypothesized making telephone contact with subjects prior to hospital attendance would improve recruitment rates into clinical trials.

Retrospective post hoc analysis of recruitment rates in an on-going clinical trial was undertaken. Two hundred twelve consecutive patients were recruited over 6 months. During the first 3 months, patients received a telephone call from the research team and also received an information sheet by post prior to clinic attendance (group 1). The study was discussed on telephone and any issues were re-addressed at the patient's clinic appointment when they were formally invited to participate in the study. After 3 months, the investigators stopped telephoning the patients (group 2); patients were invited to participate in the study by post and were first spoken to directly by an investigator in clinic. The study protocol and investigators did not change between groups.

There was no significant difference in baseline demographics between the two groups. There was a significant improvement in recruitment rate in group 1 compared to group 2 (77.7% vs. 45.0%, P < 0.0001). An improvement in clinic attendance rate in group 1 was observed, although this was not significant (did not attend rate: 2.9% vs. 7.8%, P = 0.14).

Telephone contact between researchers and potential participants prior to clinic attendance can greatly improve study recruitment rates. This information may benefit the design of all clinical studies.