Estimated glomerular filtration rate at dialysis initiation and subsequent decline in residual kidney function among incident hemodialysis patients.

Background: Higher estimated glomerular filtration rate (eGFR) at dialysis initiation, known as earlier start of dialysis, is often a surrogate of poor outcomes including higher mortality. We hypothesized that earlier dialysis initiation is associated with a faster decline in residual kidney function (RKF), which is also associated with higher mortality among incident hemodialysis (HD) patients.

Methods: In a cohort of 4911 incident HD patients who initiated HD over a 5-year period (July 2001 to June 2006), we examined the trajectories of RKF, ascertained by renal urea clearance (KRU), over 2 years after HD initiation across strata of eGFR at HD initiation using case-mix adjusted linear mixed-effect models. We then investigated the association between annual change in RKF and mortality using Cox proportional hazard models.

Results: The median (interquartile range) baseline KRU was 2.20 (1.13-3.63)  mL/min/1.73 m2. The decline of KRU was faster in patients who initiated HD at higher eGFR. The relative changes with 95% confidence intervals (CIs) in KRU at 1 year after HD initiation were -1.29 (-1.28 to -1.30), -1.17 (-1.16 to -1.18), -1.11 (-1.10 to -1.12) and -0.78 (-0.78 to -0.79)  mL/min/1.73 m2 in the eGFR categories of ≥10, 8-<10, 6-<8 and <6 mL/min/1.73 m2, respectively. The faster decline of KRU at 1 year was associated with higher all-cause mortality (reference: ≥0 mL/min/1.73 m2): hazard ratios (95% CIs) for change in KRU of -1.5 to <0, -3 to less than -1.5 and less than -3 mL/min/1.73 m2 were 1.20 (1.03-1.40), 1.42 (1.17-1.72) and 1.88 (1.47-2.40), respectively.

Conclusions: The faster decline of RKF happens with earlier dialysis initiation and is associated with higher all-cause mortality.