Table 1 SPIDER search strategy outline

Sample (S)

Studies in which participants included recruiters with a role in approaching potential participants (e.g. patients, carers or parents) to take part in a healthcare-related RCTs. Recruiters included both professionally registered (e.g. doctors, surgeons, physiotherapists, nurses, radiographers, GPs) and non-professionally registered (e.g. clinical trials assistants, research practitioners) members of staff

Phenomena of interest (Pi)

The phenomenon of interest in this study was recruitment to RCTs. Studies which considered recruitment alongside other trial-related activities could be included as long as the recruitment element was clearly reported and distinguishable from other trial-related activities, in so far as findings could be extracted for inclusion in analysis

Design (D)

Primary research that used qualitative approaches/designs to investigate recruiters’ views, experiences and practices/behaviour related to attempts recruiting participants into RCTs could be included. No limits on qualitative theoretical frameworks were applied. Qualitative methods of data collection included, but were not limited to, qualitative interviews (in-depth, unstructured, semi-structured and structured), focus groups and observations (participant/non-participant). The review focused on studies that reported on recruitment to particular types of RCTs: those based in the healthcare sector, and those that randomised at the individual patient (or proxy) level. Studies reporting on cluster randomised trials were not included because they were considered likely to face different challenges than RCTs that randomise at the individual level. Studies that reported results from non-human, non-healthcare, or lab-based RCTs were excluded. The definition of RCTs included pilot or feasibility studies, provided that they were randomised. Qualitative studies of recruitment to hypothetical RCTs were excluded

Evaluation (E)

This synthesis explored the subjective constructs of attitudes, experiences and practices/behaviour of those recruiting patients to RCTs

Research type (R)

The search focused primarily on qualitative research, although mixed methods research was considered for inclusion where the qualitative component was clearly defined and reported

Comparisons

It was considered likely that there would be primary reports from a range of RCTs. We therefore wanted to be able to make comparisons across specialty or clinical field (e.g. oncology and radiology), type of recruiter (e.g. registered and non-registered, nurse and doctor), level of care (e.g. primary, secondary, community) and nature of RCT treatment arms (e.g. standard care vs novel treatment, or less/no treatment). These comparisons were intended to allow for a greater level of examination of some of the intricacies of recruiting to RCTs and to yield insights that were generalisable across RCTs