All Expanded Criteria Donor Kidneys are Equal But are Some More Equal Than Others? A Population-Cohort Analysis of UK Transplant Registry Data

Survival outcomes for kidney transplant candidates based on expanded criteria donor (ECD) kidney type is unknown. A retrospective cohort study was undertaken of prospectively collected registry data of all waitlisted kidney failure patients receiving dialysis in the United Kingdom. All patients listed for their first kidney-alone transplant between 2000-2019 were included. Treatment types included; living donor; standard criteria donor (SCD); ECD⁶⁰ (deceased donor aged ≥60 years); ECD^50-59 (deceased donor aged 50-59 years with two from the following three; hypertension; raised creatinine and/or death from stroke) or remains on dialysis. The primary outcome was all-cause mortality, with time-to-death from listing analyzed using time-dependent non-proportional Cox regression models. The study cohort comprised 47,917 waitlisted kidney failure patients, of whom 34,558 (72.1%) received kidney transplantation. ECD kidneys (n = 7,356) were stratified as ECD⁶⁰ (n = 7,009) or ECD^50-59 (n = 347). Compared to SCD, both ECD⁶⁰ (Hazard Ratio 1.126, 95% CI 1.093-1.161) and ECD^50-59 (Hazard Ratio 1.228, 95% CI 1.113-1.356) kidney recipients have higher all-cause mortality. However, compared to dialysis, both ECD⁶⁰ (Hazard Ratio 0.194, 95% CI 0.187-0.201) and ECD^50-59 (Hazard Ratio 0.218, 95% CI 0.197-0.241) kidney recipients have lower all-cause mortality. ECD kidneys, regardless of definition, provide equivalent and superior survival benefits in comparison to remaining waitlisted.