OBJECTIVE: Recruitment of so called rare populations, including refugees, for participation in research studies is challenging. We aim to share our lessons learned regarding recruitment strategies used in the "Sanadak" trial, a randomized controlled trial for the evaluation of a self-help app for Syrian refugees with posttraumatic stress.
METHODS: We conducted an interim evaluation of our recruitment strategies. A quantitative analysis addressed how potential study participants first learned about "Sanadak" and in which way they made first contact with us. A qualitative part included problem-centered interviews with our Syrian study nurses (n=3) regarding the success of various recruitment strategies and perceived barriers.
RESULTS: Data were available for the recruitment of 140 Syrian refugees. Almost half of the sample (44%) was recruited via personal contact, about another third (36%) by means of study promotion (e. g. Facebook ads), and about a fifth (19%) through multipliers. Typical barriers were concerns regarding data protection, anonymity and stigmatization.
DISCUSSION: Snowball sampling was an effective recruitment strategy in our trial. This is also the most acknowledged recruitment strategy for rare populations. In addition, other strategies were useful to increase sample variance. The interim evaluation helped to direct efforts towards effective recruitment strategies and to identify and address barriers.
CONCLUSION: Multi-strategic recruitment with a focus on snowball sampling, multiple options to make contact with the study team, and having culturally sensitive members in the study team contributed towards successful recruitment in the "Sanadak"-trial.