Mortality in the Veneto population on renal replacement therapy

Abstract

This section reports survival rates for patients on renal replacement therapy (RRT). The data obtained from the Veneto Dialysis and Transplantation Registry (VDTR) cover the whole population in the region. Patients on RRT alive on 31 December of each year were assumed to be at risk of dying in the following year. Furthermore, time-to-event analysis was used to describe the complete history of patients from when they started RRT until they died, including transitions between the 3 main treatment modalities - hemodialysis (HD), peritoneal dialysis (PD) and renal transplantation. The cohort of patients starting RRT from 1998 to 2010 was followed up until 31 December 2010. Survival rates from the first treatment to death were calculated according to the life table method. Relative survival and excess mortality rates were estimated according to the Ederer II method. A multistate model was used to describe changes in a patient's condition (changes of treatment, or death) over time. Among prevalent patients on RRT, the annual risk of death was 10.65% in 2008, 9.35% in 2009 and 8.86% in 2010. The overall mortality rate was 12.5 per 100 patient-years (95% confidence interval [95% CI], 12.1-13.0). The 5-year relative survival was 59% (95% CI, 57%-60%), and at 10 years relative survival was 41% (95% CI, 39%-43%); the estimated excess mortality rate was very high at the start of RRT (18 per 100 patient-years) but gradually decreased after the second year. On multivariate analysis, excess mortality was associated with age and primary renal diseases. Less than 10% of patients starting on PD shifted to HD in the first year of RRT, and a considerable proportion received a transplant, amounting to 6% in the first year, and thereafter increasing steadily: at the end of the fifth year, 34% of patients starting RRT on PD had received a transplant. HD patients behaved differently: any shift to PD was negligible, and the patients receiving a transplant amounted to only 2% in the first year and about 16% by the end of the fifth year. Cumulative mortality among HD patients was particularly high (already 18% at 1 year, and 70% at 10 years) by comparison with those on PD (8% at 1 year, 54% at 10 years). Although mortality on RRT is not particularly high in Veneto by comparison with countries other than Italy, this result is mainly due to an increasing number of patients receiving transplants, which makes them a favorably selected population. The mortality rate was high among those on HD, particularly in the first year. Our population on RRT is rather heterogeneous, and a description of the outcomes based only on the whole population may be misleading.