Survival in patients treated by long-term dialysis compared with the general population

BACKGROUND: Relative survival, a methodology previously used in epidemiologic studies of cancer, compares the observed survival of a patient cohort with expected survival derived from general population life tables. We examined relative survival in patients treated by long-term dialysis in the Italian Dialysis and Transplantation Registry in order to determine the prognosis of dialysis patients. STUDY DESIGN: Cohort study drawn from a registry. SETTING & PARTICIPANTS: Patients enrolled in the Italian Dialysis and Transplantation Registry. FACTORS: Sex, age, primary kidney disease, renal replacement therapy modality, and main comorbid conditions. OUTCOMES: Death from any cause. MEASUREMENTS: Relative survival ratio (the ratio of observed survival in the population of interest to the survival expected given the age- and period-specific mortality of the general population) and excess mortality rate (difference between observed and expected mortality rates). RESULTS: In January 2000 to December 2008, a total of 27,642 patients were included. The 5-year relative survival estimate was 55.6% (95% CI, 54.7%-56.5%). The excess mortality rate showed a peak at 3 months (21 deaths/100 patient-years), then decreased, becoming constant from the end of year 1 to year 8, with leveling off at about 10 deaths/100 patient-years. Older age, systemic diseases, and diabetes showed the strongest association with excess mortality. Peritoneal dialysis was associated with a lower relative excess risk in only the first year of treatment. LIMITATIONS: The patient cohort comprises about half the Italian patients beginning dialysis therapy in the period. CONCLUSIONS: This study highlights the applicability of relative survival methods in dialysis patients. This measure allows estimation of disease prognosis and severity comparisons among chronic diseases. The excess mortality rate appears to be a more sensitive and informative measure than the simple proportion of survivors.