Association of pretransplant renal replacement therapy duration with outcome in kidney transplant recipients: a prevalent cohort study in Slovenia.

The effect of renal replacement therapy (RRT) duration on kidney transplant outcome is controversial. The aim of this study was to analyze the association between pretransplant RRT duration versus patient and graft survival. The study cohort included 445 recipients of a deceased-donor kidney transplant between January 2000 and December 2009. Pretransplant RRT duration as a continuous variable and divided into time categories was the risk factor of interest. Patient and death-censored graft survival were the outcomes. Survival since the onset of RRT was calculated to avoid lead-time bias. Median pretransplant RRT duration was 4.7 years. The duration of RRT was longer in 33 patients who died (median 6.8 vs. 4.6 years; P = 0.022) and 56 patients who lost their graft (5.7 vs. 4.6 years; P = 0.035). Pretransplant RRT duration, as a continuous variable, was associated with a non-significant increase in the risk of recipient death (hazard ratio [HR] 1.01 per year of RRT; P = 0.09) and death-censored graft loss (HR 1.02; P = 0.12). When RRT was studied as a categorical variable, the mortality risk reached statistical significance when the patient had been on RRT for more than 4.7 years (HR 2.12; P = 0.042). Pretransplant RRT duration was not associated with an increased risk for recipient death if patient survival was calculated since the onset of RRT (HR 0.98 per year; P = 0.21). This study suggests that a longer RRT duration negatively impacts on post-transplant patient and graft survival; however, when pretransplant patient survival is accounted for, RRT duration has no significant effect on patient outcome.