Is the decline of renal function different before and after the start of dialysis?

BACKGROUND: The presence of glomerular filtration in dialysis patients is associated with improved survival and quality of life. This study explores the time course of the glomerular filtration rate (GFR) between 1 year before and 1 year after the start of haemodialysis (HD) and peritoneal dialysis (PD). METHODS: This study included 1861 incident dialysis patients (NECOSAD cohort; 62% male, 60 ± 15 years, 61% HD, GFR 5.2 ± 3.6 mL/min/1.73 m(2)). A decline of the GFR was estimated using linear mixed-effects models adjusted for age, sex, primary kidney disease, cardiovascular disease and diabetes. The rate of decline was allowed to change at a certain point in time. RESULTS: The decline of the GFR attenuated from -0.53 mL/min/1.73 m(2)/month (95% CI: -0.58, -0.48) in the period before the start of dialysis to -0.12 (95% CI: -0.20, -0.04) at 2-4 months of dialysis in all patients. In HD, decline attenuated from -0.51 (95% CI: -0.57, -0.44) to -0.14 (95% CI: -0.26, -0.02); in PD from -0.55 (95% CI: -0.62, -0.48) to -0.11 (95% CI: -0.23, 0.01). In patients who started dialysis with a GFR equal/above median GFR at dialysis start, the decline attenuated (at 3 months) from -0.70 (95% CI: -0.78; -0.62) to -0.21 (95% CI: -0.36; -0.05). In patients who started dialysis with a GFR below median GFR at dialysis start, the decline attenuated (at 1 month) from -0.73 (95% CI: -0.88; -0.58) to -0.04 (95% CI: -0.27 , 0.19). CONCLUSIONS: The apparent decline of the GFR slows down after 2-4 months of dialysis. This decline was similar in HD and PD patients, although at a different level of GFR. Further studies are needed to examine explanations for this phenomenon.