Calculation of Kt/V and creatinine [correction of creatine] clearance in APD

The calculation of Kt/V and creatinine clearance per 1.73 m2 of body surface area (CrCl/1.73 m2 of BSA) varies according to whether the post- or pre-nightly dialysis treatment (NDT) values of the serum urea (sUrea), serum creatinine (sCreat), and body weight (BW) parameters are used. The purpose of this paper is to determine the difference between Kt/V and CrCl/1.73 m2 of BSA, calculated using the pre- and post-NDT values, and any correlation of such differences with different automated peritoneal dialysis (APD) methods. We took into consideration patients on APD treated using the tidal method with four different techniques: NTPD (9 patients; no daytime dwell), NTPD-1 (12 patients; one daytime dwell of 4-7 hours), CTPD (10 patients; one daytime dwell), and CTPD-2 (8 patients; two daytime dwells). Body water (V) and body surface area (BSA) were calculated using the Watson and Du Bois formulas. The percentage difference between pre- and post-NDT using the various methods is not statistically significant, while all the post-NDT parameters are significantly lower than the pre-NDT parameters. Since this difference is greater for sUrea (8.8%) and V (1.1%) than for sCreat (4.1%) and BSA (0.8%), the nightly Kt/V variation (11.2%) is greater than the nightly CrCl/1.73 m2 of BSA variation (5.2%). These variations do not differ significantly among the various methods. For APD, therefore, increase is to be expected in the CAPD targets of 10% and 5% respectively for Kt/V and CrCl/1.73 m2 of BSA calculated using the post-NDT values of sUrea and sCreat and the pre-NDT value of BW.