The optimal ranges of serum calcium, phosphorus and intact parathyroid hormone in peritoneal dialysis patients

Objective To explore the optimal levels of serum calcium, phosphorus and intact parathyroid hormone (iPTH) in peritoneal dialysis (PD) patients. Methods This study is a single center, retrospective cohort study. The associations between serum calcium, phosphorus and iPTH and all-cause mortality in 217 PD patients were analyzed. All patients started PD between January 1, 2008 and April 30, 2016 were enrolled and followed up to December 31, 2016. At baseline and every 3 months, biochemical and therapeutic information was collected. Cox proportional hazard regression models and cubic splines analysis were employed to assess the lowest mortality risk ranges in serum markers of bone metabolism. Results There was no significantly difference between patients within target ranges based on KDOQI or KDIGO guideline and those outside the target ranges by Kaplan-Meier survival analysis. The lowest mortality risk ranges were 2.17-2.40 mmol/L for serum calcium, 1.20-1.67 mmol/L for serum phosphorus and 180-350 ng/L for serum iPTH by using Cox models and cubic splines analysis. Moreover, cumulate survival had significant difference between patients within the descriptive ranges and those out of the descriptive ranges at time-averaged values but not at baseline values. Conclusions The optimal time-averaged ranges of PD patients are 2.17-2.40 mmol/L for serum calcium, 1.20-1.67 mmol/L for serum phosphorus and 180-350 ng/L for serum iPTH. These ranges need further validation by large population studies to further conform. Key words: Peritoneal dialysis; Parathyroid hormone; Calcium; Phosphorus