The US Renal Data System and the Case-Mix Severity Study.

The US Renal Data System (USRDS), established in 1988 to collect and analyze information on end-stage renal disease (ESRD) patients in the United States and their treatment, is briefly described. A number of special studies have been undertaken by the USRDS. One of these is the Case-Mix Study, which reviewed data from an incident sample of 4,911 patients starting dialysis in 1986 and 1987 who were monitored for 1 to 4 years. Analysis included Cox proportional hazard modeling, which allowed quantification of the effect of various comorbid factors on mortality. Relevant findings included a greater mortality in diabetic patients treated by continuous ambulatory peritoneal dialysis (CAPD) compared with those treated by center hemodialysis. With regard to adequacy of dialysis, prescribed dialysis averaged a Kt/V of 1.0, with 53% of patients having a value of 1.0 or less. Where delivered Kt/V could be calculated, the mean of this was 0.72. The prescribed Kt/V in this sample of patients did not predict mortality, but there was a statistically significant inverse correlation of delivered Kt/V with mortality. It would appear a significant number of patients were being underdialyzed in the United States in 1986 and 1987. The means by which to obtain further information from the USRDS is described.