Retrieval of individual patient data depended on study characteristics : a randomized controlled trial

OBJECTIVE: To examine the effect of providing a financial incentive to authors of randomized clinical trials (RCTs) to obtain individual patient data (IPD). STUDY DESIGN AND SETTING: Parallel-group RCT with authors identified in the RCTs eligible for two systematic reviews. The authors were randomly allocated to the intervention (financial incentive with several contact approaches) or control group (using the same contact approaches). Studied outcomes: proportion of authors who provided IPD, time to obtain IPD, and completeness of IPD received. RESULTS: Of the 129 authors contacted, 37 authors suggested or contacted a person/funder providing relevant details or showed interest to collaborate, while 45 authors directed us to contact a person/funder, lacked resources/time, did not have ownership/approval to share the IPD, or claimed IPD was too old. None of the authors shared their IPD. We contacted 17 sponsors and received two complete IPD datasets from one sponsor. The time to obtain IPD was >1 year after a sponsor's positive response. Common barriers included study identification, data ownership, limited data access, and required IPD licenses. CONCLUSIONS: IPD sharing may depend on study characteristics, including funding type, study size, study risk of bias, and treatment effect, but not on providing a financial incentive. TRIAL REGISTRATION: Clinical Trials.gov (NCT02569411), registered on October 5th, 2015.