Background: Both dialysis dose and residual kidney function (RKF) contribute to solute clearance and are associated with outcomes in hemodialysis patients. We hypothesized that the association between dialysis dose and mortality is attenuated with greater RKF.
Methods: Among 32 251 incident hemodialysis patients in a large US dialysis organization (2007-11), we examined the interaction between single-pool Kt/V (spKt/V) and renal urea clearance (rCLurea) levels in survival analyses using multivariable Cox proportional hazards regression model.
Results: The median rCLurea and mean baseline spKt/V were 3.06 [interquartile range (IQR) 1.74-4.85] mL/min/1.73 m2 and 1.32 ± 0.28, respectively. A total of 7444 (23%) patients died during the median follow-up of 1.2 years (IQR 0.5-2.2 years) with an incidence of 15.4 deaths per 100 patient-years. The Cox model with adjustment for case-mix and laboratory variables showed that rCLurea modified the association between spKt/V and mortality (Pinteraction = 0.03); lower spKt/V was associated with higher mortality among patients with low rCLurea (i.e. <3 mL/min/1.73 m2) but not among those with higher rCLurea. The adjusted mortality hazard ratios (aHRs) and 95% confidence intervals of the low (<1.2) versus high (≥1.2) spKt/V were 1.40 (1.12-1.74), 1.21 (1.10-1.33), 1.06 (0.98-1.14), and 1.00 (0.93-1.08) for patients with rCLurea of 0.0, 1.0, 3.0 and 6.0 mL/min/1.73 m2, respectively.
Conclusions: Incident hemodialysis patients with substantial RKF do not exhibit the expected better survival at higher hemodialysis doses. RKF levels should be taken into account when deciding on the dose of dialysis treatment among incident hemodialysis patients.