Background Recruitment of participants into large clinical trials may be challenging and costly. Utilization of limited resources to maximise the yield is crucial. We sought to compare costs of different recruitment strategies.

Methods To recruit 600–800 HIV discordant couples, we explored different recruitment strategies: referrals from voluntary HIV counselling and testing (VCT) centres and Home based counselling and testing (HBCT) and referrals from participants involved in a previous clinical trial. In the three strategies, we implemented accelerated mobilisation through public address system, radio talk shows and the couples ambassador model (where influential peers encourage couples HIV counselling and testing). Direct cost computation was the total amount of money spent per strategy. VCT and HBCT costs included counsellors training, cost of communication and transport reimbursement for participants’ visits. The previous study participants’ recruitment costs included communication and transport.

Results Between August 2008 and October 2010, 2060 HIV discordant couples were referred for screening. VCT, 1666(80.9%) from VCT; HBCT, 345(16.7%); and 49(2.4%) by participants from earlier trial. The cost per strategy for VCT was $81,973, HBCT $ 2,300 and Previous study participants recruitment$327; the yield per strategy was VCT 440/1666(26.4%), HBCT 161/345(46.7%) and previous study participant recruitment 28/49 (57.1%). However, VCT and HBCT contributed the most to enrollment at the study site 440/629(70%) and 161/629(26%) respectively. The average cost per couple referred from VCT was $49, HBCT was $7 and previous study participant recruitment was $7. This translates to average cost of couples enrolled to $63.

Conclusion VCT strategy was most costly compared to those from previous clinical trial and HBCT; however, it yielded the highest enrolment. Multiple strategies are recommended for successful recruitment. This computation does not take into account staff time for each of the strategies listed.