Urea kinetics has limited relevance in assessing adequacy of dialysis in CAPD

The application of urea kinetics to CAPD is controversial. Additional data is presented from our recent study on this topic. Different methods of calculating KT/V and normalized protein catabolic rate (PCRN) are compared and KT/V is shown to be on average 6.5% higher when V is calculated by Watson's formulae instead of by body weight alone. This discrepancy increases with time. It is also shown that standard methods may overestimate KT and underestimate PCRN. KT/V and PCRN by these different methods do not correlate with clinical outcomes. However, if V is calculated by Watson's formulae, there is a significant excess of deaths when KT/V is under 0.5 (weekly KT/V under 1.5). Survival curves show that neither initial KT/V nor PCRN predict failure on CAPD.