Modality of chronic renal replacement therapy and survival--a complete cohort from Finland, 2000-2009

Studies on dialysis modality and survival have shown conflicting results, mostly due to insufficient and varying control of confounding factors. Using comprehensive data on a well-defined patient cohort, we therefore investigated the association of dialysis modality with survival on chronic renal replacement therapy (RRT) and whether this association varies between subgroups of patients. Survival analyses included all adult patients entering chronic RRT in Finland between 2000 and 2009 and used information obtained from the Finnish Registry for Kidney Diseases and the Finnish Kidney Transplant Registry. In our primary intention-to-treat (ITT) analysis, we calculated relative risk of death according to dialysis modality on Day 91 from RRT start, comparing peritoneal dialysis (PD) to haemodialysis (HD). Relative risks were adjusted for putative confounders. Interactions between treatment groups and other variables were estimated. Of the total 4463 patients, 42% died during the 10 years of follow-up. Median survival time was 5.2 years. In unadjusted ITT analysis, relative risk of death of PD patients was 0.65 (95% CI 0.58-0.73, P < 0.001) compared with HD patients. With adjustment for 26 variables, the corresponding relative risk of death was 1.07 (95% CI 0.94-1.22, P = 0.33). When censoring at time of kidney transplantation, the result was similar with a relative risk of death of 1.09 (95% CI 0.95-1.25, P = 0.24) on PD compared with HD. PD is associated with several factors generally related to good prognosis. After comprehensive adjustment for putative confounding factors with the ITT analysis approach, we found no significant difference in survival between PD and HD patients.