Abstract: 【Abstract】Objective To investigate the effect of phosphate clearance on serum phosphate and prognosis in primary peritoneal dialysis patients (PD) with different peritoneal transport status. Methods The patients who were primarily treated with PD and regularly followed up for more than 3 months in a single center were involved in this cross-sectional study. Their blood laboratory results in the first month of PD were collected, and their PD adequacy and peritoneal membrane function were evaluated. Serum phosphate, phosphate clearances by peritoneum and kidney, and clinical outcome were compared among PD patients with different levels of peritoneal transport functions. Results A total of 504 PD patients were enrolled in this study. Serum phosphate in the first month of PD was lower in the high peritoneal transport patients than in the low average peritoneal transport patients (F=5.452, P=0.020) and low peritoneal transport patients (F=9.441, P=0.003). The peritoneal phosphate clearance was positively related to the 4-hour creatinine D/P ratio (r=0.280, P ＜0.001) and dialysis dose (r=0.452 P＜0.001), and was negatively related to the urinary phosphate clearance (r=-0.205, P=0.020), serum phosphate (r=-0.332 P＜0.001), and glomerular filtration rate (r=0.229, P=0.004). ROC curve for the prediction of hyperphosphatemia by peritoneal phosphate clearance rate showed that the area under the curve (AUC) was 0.682 (95% CI 0.584～0.723, P＜0.001) and the cut-off value was set at 28.75 L/W; ROC curve for the prediction of hyperphosphatemia by nPCR in low average peritoneal transport patients and low peritoneal transport patients showed that the AUC was 0.660 (95% CI 0.577～0.742, P=0.001) and the cut- off value was set at 1.026 g/kg/d. COX survival model showed that older age (OR=1.055, 95% CI 1.003～1.193, P＜0.001), and hypoalbuminemia in the first month of PD (OR=0.907, 95% CI 0.871～0.945, P=0.001) were the independent risk factors for death in all PD patients, and that low urinary phosphate clearance rate was the risk factor for death (OR=0.430, 95%CI 0.213～0.866, P=0.018) only in PD patients with lower peritoneal transport function. Conclusion ①The lower the peritoneal transport function, the lower the peritoneal phosphate clearance rate and the higher the serum phosphate level. ② Low urinary phosphate clearance was the independent risk factor for all-cause mortality in PD patients with low peritoneal transport function and low average peritoneal transport function.

Key words: Peritoneal dialysis, Phosphate clearance, Serum phosphate level