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

Abstract

Abstract 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.