Background: In many healthcare contexts, evidence exists that patients who participate in research protocols (PRP) significantly differ from nonparticipants. These differences may affect the external validity of study findings, reflect access to care, and potentially explain sources of difference in patient outcomes. There is no comprehensive study evaluating PRP among transplant recipients.
Methods: We evaluated the national Scientific Registry of Transplant Recipients from 2000 to 2008 for liver, kidney, heart, lung, and simultaneous pancreas/kidney transplant recipients in the United States for which PRP for immunosuppressive medications is reported at follow-up. Our primary aims were to evaluate participant characteristics, compare outcomes between participants and nonparticipants, and assess variability of PRP between centers and medications.
Results: The national proportions of PRP at 1 year by organ were kidney (8.2%), liver (2.9%), heart (5.0%), lung (2.6%), and simultaneous pancreas/kidney (2.8%). Factors associated with PRP included recipients' educational attainment, insurance, race/ethnicity, gender and age, donor age, transplant number, income, distance to center, and center volume. Graft and patient survivals were significantly higher among PRP for kidney, liver, and lung transplant recipients. PRP varied markedly between centers (range, 0%-58%) and by immunosuppressant medications.
Conclusions: There are systematic differences between participants and nonparticipants in research in the transplant population that may affect the external validity of research findings. Superior outcomes among participants may suggest that participation in research itself affords certain benefits. Future research evaluating the mechanisms for differential participation rates and improved survival among participants is needed.