Responses from corresponding authors of protocol publications
In total, 27 (27/96, 28%) responses (survey 1 19/55; survey 3 8/41) were received from corresponding authors of protocol publications.Most indicated that their external pilot trial was in the reporting or dissemination stage (18/27, 67%). Of these, five respondents indicated that they had published their external pilot trial findings, yet these five publications were not identified when searching the literature. The other 13 respondents indicated that they had not yet published their external pilot trial findings but intend to in the future. Nine respondents described that their external pilot trial was still in set up (2/27, 7%), conduct (4/27, 15%), or analysis (3/27, 11%) stage at the time of survey completion, and therefore were unable to complete all their respective surveys (survey 1 and survey 3).