#5768 association of high serum phosphorus with increased mortality risk in patients on peritoneal dialysis: results from colombia

Abstract Background and Aims Elevated levels of serum phosphorus (PO4) in patients with kidney failure are associated with complications such as cardiovascular (CV) disease, bone disease and impaired wound healing, and increased mortality in hemodialysis patients. A recent PDOPPS study (Lopes et al NDT 2023) showed that high PO4 is associated with increased mortality also in patients undergoing peritoneal dialysis (PD). We explored PO4 levels in a large cohort of patients undergoing chronic PD in Colombia to determine the association of PO4 levels with mortality. Method In an observational study of 8113 prevalent PD patients treated with APD (n = 2692) or CAPD (n = 5421), PO4 levels together with demographic and clinical data, including dialysate to plasma ratio of creatinine at 240 min (D/PCr240min at peritoneal equilibration test) and body mass index (BMI), were recorded. During follow-up for a median of 1.99 years, 3169 patients died, and 988 patients underwent kidney transplantation (KT). We divided patients into 5 groups (P1 to P5) according to their baseline PO4 levels (first available measurement) with the following cut-off values for groups: up to 3.5, 4.5, 5.5, 6.5, and over 6.5 mg/dL, respectively. The association of baseline PO4 levels with all-cause and CV mortality risk was analyzed with a competing-risk regression model and KT as a competing risk. Results Characteristics of patients classified into groups P1 (16%), P2 (33%), P3 (27%), P4 (13%), and P5 (9%) are presented in Table. P5-patients were in general younger, more often men, less often diabetic (DM), and had lower hemoglobin (Hb) and serum albumin compared to P1-patients. All-cause mortality risk (after adjusting for age, sex, BMI, albumin, Hb, D/PCr240min, residual renal function, DM, and hypertension) was increased in P4- and P5-patients compared with P2-patients, sub-hazard ratio (sHR) of 1.14 (95% Cl: 1.01-1.27) and sHR of 1.27 (95% Cl: 1.10-1.46), respectively. Higher PO4 levels were not associated with significantly increased CV mortality risk for P4-patients, sHR of 1.10 (95% Cl: 0.93-1.31), or for P5-patients, sHR = 1.14 (95% Cl: 0.93-1.39) compared to P2-patients. Conclusion Among 8113 PD patients in Colombia, 49% had baseline PO4 >4.5 mg/dL and 22% PO4 > 5.5 mg/dL. Baseline PO4 levels > 5.5 mg/dL (P4 and P5 groups) were associated with increased all-cause mortality. These results are in agreement with the results of the PDOPPS study and suggest that effective management of hyperphosphatemia is important to improve clinical outcomes in PD patients.