Associations of calcium, phosphate and intact parathyroid hormone levels with mortality, residual kidney function and technical failure among patients on peritoneal dialysis

BACKGROUND: Associations of calcium, phosphate and intact parathyroid hormone (iPTH) levels with outcomes may be different between patients on peritoneal dialysis (PD) and hemodialysis (HD). The aim of the study is to evaluate these associations among PD patients. METHODS: In this prospective cohort study on the Japan Renal Data Registry, adults on PD at the end of 2009 were included. The observation period was until the end of 2018 and the data were censored at the time of transplantation or transition to HD. Exposures were time-averaged or time-dependent albumin-corrected calcium (cCa), phosphate and iPTH levels. Outcomes were all-cause and cardiovascular mortality, transition to HD and urine output. Data were analyzed using Cox regression models or linear mixed-effects models and the results were shown as cubic spline curves. RESULTS: Among 7393 patients, 590 deaths and 211 cardiovascular deaths were observed during a median follow-up of 3.0 years. Higher cCa and phosphate levels were associated with higher mortality. Lower cCa levels were associated with a faster decline, whereas lower phosphate was associated with a slower decline in urine output. Lower phosphate and iPTH levels were associated with a lower incidence of transition to HD. CONCLUSIONS: Among PD patients, the observed associations of cCa, phosphate and iPTH with mortality, residual kidney function and technical failure suggest that avoiding high cCa, phosphate and iPTH levels might improve outcomes.