Table 2 Data extraction for study characteristics and context

•Each paper included in the search was assigned a unique number. This was recorded, along with whether the paper had been an initial ‘yes’ or ‘maybe’

•Author (first)

•Publication date

•Journal

•Country of study

•Data collection method(s)

•Data analysis method(s)

•Sample size

•Data collection period

•Number of RCTs from which data is drawn

•Healthcare setting

•Adult or paediatric

•Intervention(s)

•Comparator(s)

•Interviewee profession

•Experience of recruiters in recruiting (as quantified by authors, often number of patients recruited or years of recruitment experience)

•E.g. whether the findings had already been reported elsewhere, or if anything key was missing (e.g. number of participants)