Do clinical trials reflect reality? A systematic review of inclusion/exclusion criteria in trials of renal transplant immunosuppression.

Renal transplant recipients and donors are becoming increasingly more marginal, with more expanded criteria (ECD) and donation after circulatory death (DCD) donors and older recipients. Despite this, high-risk donors and recipients are often excluded from clinical trials, leading to uncertainty about the generalizability of findings. We extracted data regarding inclusion/exclusion criteria from 174 trials of immunosuppression in renal transplant recipients published over a 5-year period and compared criteria with those specified in published trial registries. Frequently reported donor exclusion criteria were age (16.1%), donor type and cold ischaemic time (22.4%). Common recipient exclusion criteria included upper age limit (38.5%), high panel reactive antibody (PRA) (42.5%) and previous transplantation (39.7%). Inclusion/exclusion criteria recorded in trial registries matched those reported in the manuscript in only 6 (7.8%) trials. Of registered trials, 51 (66.2%) trials included additional criteria in the manuscript, 51 (66.2%) were missing criteria in the manuscript specified in the protocol, and in 19 (24.7%) key criteria changed from the protocol to the manuscript. Our findings suggest many recent immunosuppression trials have restrictive inclusion criteria which may not be reflective of current renal transplant populations. Discrepancies between trial protocols and published reports raise the possibility of selection bias.