Tracking waitlist and kidney transplant outcomes is no easy feat. Patients who undergo transplant are cared for by many practitioners in nephrology clinics, dialysis centers, and transplant programs throughout the transplant process, creating transition points at which delays may occur or patients may be lost to follow-up. Three main data sources track pre- and post-transplant outcomes: the United Network for Organ Sharing (UNOS), which has held the contract for the Organ Procurement & Transplantation Network (OPTN), the main regulatory body for transplantation in the United States; the Scientific Registry of Transplant Recipients (SRTR), which provides statistical and analytic support to the public and regulatory agencies through maintenance of its own data registry; and the United States Renal Data System (USRDS), which supplements data from UNOS with social security death data from the Centers for Medicare & Medicaid Services (CMS) to monitor all individuals with kidney diseases (Figure 1).
In a recent issue of JASN, Yu et al. (1) examined the outcomes of over 300,000 transplant recipients between 2000 and 2019 from these three datasets (UNOS, SRTR, and USRDS) to measure their concordance. The authors found wide variability in number of deaths by data set. The greatest number of post-transplant deaths was reported by the USRDS. By 20 years, mortality was more than 10% higher when reported by SRTR or USRDS than when reported by UNOS. Conversely, when tracking pretransplant outcomes, UNOS captured more waitlisted patients, but USRDS still reported the greatest numbers of deaths.
Differences in data inputs explain some of these discrepancies. For example, the UNOS registry no longer has access to the complete Social Security Death Master File (2), so it likely underestimates the death rate. CMS is notified of all patients initiating chronic dialysis and could identify kidney graft failures independent of transplant programs, but these data are not systematically cross-referenced by UNOS, again resulting in discrepancies (3).
Based on these findings, the data-sharing and cross-referencing processes currently in place appear to be inadequate. Policymakers should mandate data sharing and transparency among federally funded registries and have a validated, unified definition of ascertainment of key outcomes, including death and dialysis initiation, to ensure consistency and accuracy of kidney transplant data. Researchers may consider USRDS to report the greatest number of post-transplant deaths, whereas UNOS is more accurate for waitlisted patients, and should be careful to use the appropriate data source when analyzing corresponding transplant outcomes.
Sack K. Researchers wring hands as U.S. clamps down on death record access. The New York Times. October 8, 2012. Accessed September 15, 2023. https://www.nytimes.com/2012/10/09/us/social-security-death-record-limits-hinder-researchers.html