Relationship between urea reduction ratio, demographic characteristics, and body weight for patients in the 1996 National ESRD Core Indicators Project

The 1996 Health Care Financing Administration's (HCFA) Core Indicators Project for in-center, hemodialysis patients collects information on the quality of care delivered in four clinical areas that were anticipated to predict patient outcomes. Included among these clinical performance measurements is the delivered dose of hemodialysis, measured by the fractional reduction of urea achieved during a single hemodialysis session (urea reduction ratio [URR]). A random sample (N = 7,310) of adult (aged ≥ 18 years), in-center hemodialysis patients was selected, and a one-page data collection form for each patient was sent to the dialysis facility in which care was provided during the last quarter of 1995. The dialysis facilities provided information for 6,861 (94%) patients, and at least one paired predialysis and postdialysis blood urea nitrogen (BUN) concentration was reported for 6,655 (97%) of these patients. The URR of this cohort was 65.5% ± 8.0% (mean ± SD), and 41% of patients had a URR less than 65%. The mean dialysis session length was 203 minutes, and more than half of the patients received dialysis with a dialyzer membrane with a KUf less than 10 mL/mm Hg/h. The patients with a URR less than 65% had a mean body weight approximately 10 kg greater than patients with a URR of 65% or greater. This relationship was present for all demographic characteristics studied, including age, gender, race, and primary cause of end-stage renal disease (ESRD). Patients receiving dialysis for less than 6 months were more likely to have a URR less than 65% than patients on dialysis for longer periods. By multivariate analysis, variables significantly associated with a delivered URR less than 65% were body weight in the heaviest quartile (odds ratio [OR] = 6.1), male gender (OR = 2.6), on dialysis therapy less than 6 months (OR = 2.5), youngest quartile of age (<49 years) (OR = 2.0), lowest quartile of serum albumin values less than 3.6 g/dL (bromcresol green method) or less than 3.3 g/dL (bromcresol purple method) (OR = 1.6), black (OR = 1.5), dialyzed with a dialyzer KUf less than 20 mL/mm Hg/h (OR = 1.8), lowest quartile hematocrit (<29.7%) (OR = 1.2), and shorter dialysis session length (OR = 1.02/min). In conclusion, both patient-specific demographic variables and treatment-specific parameters are significantly associated with ESRD patients receiving a URR less than 65%. Furthermore, these data suggest statistically significant linkages between the delivered dose of hemodialysis and other independent outcome predictors such as serum albumin concentration. Prospective study is required to determine whether intervention strategies to improve the delivered dose of hemodialysis will affect this outcome predictor or whether serum albumin and dialysis dose share a common cause not amenable to increasing the URR.