Dialysis vintage and outcomes in renal transplantation

Pre-emptive kidney transplantation is the recommended strategy for patients with end-stage renal failure in all guidelines [Kidney Disease: Improving Global Outcomes (KDIGO), The Australian and New Zealand Dialysis and Transplantation Registry (ANZDATA), European Renal Best Practice Guideline (ERBP), British Transplant Society (BTS)]. This recommendation is intuitive and based on few older studies with considerable limitations. In addition, there is conflicting evidence as to whether the duration of dialysis vintage impacts on graft and patient survival after transplantation. The objective of this structured review was to critically review the published evidence on dialysis vintage and outcomes by including the most recent papers on that topic. We searched Medline using keywords for kidney transplantation, pre-emptive, dialysis vintage and relevant outcomes, and found 14 eligible cohort studies. The best evidence was found for pre-emptive transplantation, which was found to be associated with a lower risk of actual graft loss (including death as event) compared with non-pre-emptive transplantation. When only patients were considered that have been registered pre-emptively but then received or did not receive a pre-emptive transplant, the association with functional graft survival (excluding death as event) was only marginal. Dialysis vintage had a graded association with patient survival in most of the studies, but an unclear estimate with functional graft survival. Older studies also found an association of dialysis vintage with death-censored graft survival, but this association is likely confounded by selection and the competing risk of death and was no longer observed in recent eras, i.e. in transplants performed in the last decade. In summary, the recommendation for pre-emptive kidney transplantation for optimal patient and graft survival remains valid even in recent periods but the association of dialysis vintage after dialysis initiation with death-censored graft survival is less clear. The association of dialysis vintage with mortality after transplantation depends on the median duration of dialysis of the wait-listed population as well as acceptance rates for transplantation, and may thus be country specific. Nevertheless, it is reasonable to advocate pre-emptive kidney transplantation in all age groups. What remains unsolved is the selection issues since the reasons for longer waiting time on dialysis are difficult to capture in retrospective observational studies, and lead time as well as immortal time bias may have confounded the mortality data.