Dialysis Vintage and Outcomes after Kidney Transplantation: A Retrospective Cohort Study

Abstract

Background and objectives: Historically, length of pretransplant dialysis was associated with premature graft loss and mortality after kidney transplantation, but with recent advancements in RRT it is unclear whether this negative association still exists.

Design, setting, participants, &measurements: This is a retrospective cohort study evaluating 6979 first kidney allograft recipients from the Austrian Registry transplanted between 1990 and 2013. Duration of pretransplant dialysis treatment was used as categoric predictor classified by tertiles of the distribution of time on dialysis. A separate category for pre-emptive transplantation was added and defined as kidney transplantation without any dialysis preceding the transplant. Outcomes were death-censored graft loss, all-cause mortality, and the composite of both.

Results: Median duration of follow-up was 8.2 years, and 1866 graft losses and 2407 deaths occurred during the study period. Pre-emptive transplantation was associated with a lower risk of graft loss (hazard ratio, 0.76; 95% confidence interval, 0.59 to 0.98), but not in subgroup analyses excluding living transplants and transplants performed since 2000. The association between dialysis duration and graft loss did not depend on the year of transplantation (P=0.40) or donor source (P=0.92). Longer waiting time on dialysis was not associated with a higher rate of graft loss, but the rate of death was higher in patients on pretransplant dialysis for >1.5 years (hazard ratio, 1.62; 95% confidence interval, 1.43 to 1.83) compared with pretransplant dialysis for <1.5 years.

Conclusions: Our findings support the evidence that pre-emptive transplantation is associated with superior graft survival compared with pretransplant dialysis, although this association was weaker in transplants performed since 2000. However, our analysis shows that length of dialysis was no longer associated with a higher rate of graft loss, although longer waiting times on dialysis were still associated with a higher rate of death.

Keywords: allografts; chronic dialysis; cohort studies; death; follow-up studies; graft survival; humans; kidney transplantation; liver transplantation; outcomes; registries; renal dialysis; renal replacement therapy; retrospective studies; tissue donors; transplantation.

Figure 1.

Cumulative incidence curves for death-censored graft loss stratified by duration of pretransplant dialysis. The number of patients at risk in each stratum at various follow-up times is shown in the bottom panel.

Figure 2.

Forest plot of Fine and Gray models for death-censored graft loss and Cox models for mortality and the composite outcome of death-censored graft loss and mortality. Crude and adjusted hazard ratio estimates and corresponding 95% confidence intervals associated with duration of pretransplant dialysis are shown for death-censored graft loss in panel (A), mortality in panel (B), and the composite outcome in panel (C). Confounding variables for adjustment in the “clinical model” were selected on the basis of clinical judgment and by purposeful selection algorithm in the “purposeful model.” Tertile 1 (pretransplant dialysis for up to 1.5 years) was used as reference group in all models. LDTX, living donor transplants; TX, transplant.

Figure 3.

Kaplan-Meier curves of all-cause mortality stratified by duration of pretransplant dialysis. The number of patients at risk in each stratum at various follow-up times is shown in the bottom panel.