Within-center correlation in dialysis adequacy

The purpose of this study was to determine whether patients with end stage renal disease treated with hemodialysis were correlated in dialysis adequac y within facilities. This was a retrospective analysis of dialysis adequacy based on urea reduction ratio (URR) values from 6969 patients dialyzed at 154 facilities. The within-center correlation was quantified using the betw een-center variation and the parameter rho that was derived using ANOVA tab les and mixed effects models. The variation in center means for URR was wid er than expected for independent observations (52.9-76.1 versus 60.7-73.8, respectively). Furthermore, there was a significant within-center correlati on in URR values across all facilities (rho = 0.136, P < 0.0001), which per sisted after adjusting for patient specific covariates, facility characteri stics, and state. In conclusion, there was a substantial within-center corr elation in dialysis adequacy that reflected important center effects on the outcome of ESRD patients. (C) 2000 Elsevier Science Inc. All rights reserv ed.