Agreement between different parameters of dialysis dose in achieving treatment targets: results from the NECOSAD study.

BACKGROUND: The recommended parameter of dialysis dose differs between K-DOQI and the European Best Practice Guidelines. It is not well known to what extent an agreement exists between the different parameters, nor if target and delivered dialysis dose are prescribed according to the urea reduction rate (URR), single-pool Kt/V (spKt/V) or equilibrated double-pool Kt/V (eKt/V) and which parameter is most strongly related to mortality. METHODS: In 830 haemodialysis patients from the NECOSAD cohort URR, spKt/V and eKt/V were calculated and compared according to a classification regarding the recommended treatment targets (70%, 1.4 and 1.2, respectively) as well as minimum delivered dialysis dose (65%, 1.2 and 1.05, respectively). Moreover, the relation between treatment dose and survival was assessed using Cox regression analysis. RESULTS: A spKt/V of >/=1.4 and URR >/=70% corresponded with eKt/V >/=1.20 (as reference method) in, respectively, 98.0 and 90.6% of patients. spKt/V of >/=1.2 and URR >/=65% corresponded with eKt/V >/=1.05 in, respectively, 95.5 and 91.2% of patients. Deviations from the reference method were significantly related to differences in urea distribution volume (spKt/V), treatment time (URR) and ultrafiltration volume (URR). The adjusted HR (95% CI) was 0.98 (0.96, 0.99) for URR, 0.51 (0.31, 0.84) for spKt/V and 0.46 (0.30, 0.80) for the eKt/V. CONCLUSION: The use of URR leads to larger disagreement with the reference method (eKt/V) treatment target as compared to spKt/V. Low urea distribution volume, short treatment time and low ultrafiltration volumes are predictive parameters for overestimation of dialysis dose when utilizing the alternative methods spKt/V and URR instead of eKt/V. Delivered eKt/V, spKt/V and URR were all positively related to survival.