Association of Serum Chloride Concentration With All-Cause and Cardiovascular Mortality in Patients Undergoing Peritoneal Dialysis: The Fukuoka Peritoneal Dialysis Registry

Rationale & Objective Low serum chloride concentration is linked to mortality in chronic kidney disease and hemodialysis, but evidence in peritoneal dialysis (PD) has largely come from incident cohorts. We evaluated whether serum chloride concentration at registry enrollment is independently associated with all-cause and cardiovascular mortality among maintenance PD patients. Study Design A multicenter retrospective cohort study Setting & Participants The Fukuoka Peritoneal Dialysis Registry (F-PDR) enrolled PD patients from 20 centers in Japan (2011–2020). Enrollment in this cohort study was not restricted to the time of PD initiation. After excluding patients with PD duration < 90 days at the F-PDR enrollment, 1,049 maintenance PD patients were analyzed. Exposure Serum chloride concentration at registry enrollment, categorized into tertiles (T1 < 96, T2 96–99, T3 > 99 mmol/L). Outcomes All-cause mortality (primary) and cardiovascular mortality (secondary). Analytical Approach Cox proportional hazards models estimated hazard ratio (HR) and 95% confidence interval (CI) with multivariable adjustment including serum sodium and other prespecified covariates. Missing covariates were handled with multiple imputation. Results Over a median follow-up of 731 days, 179 patients (17.1%) died, including 59 (5.6%) from cardiovascular causes. In the fully adjusted model, compared with T3 (> 99 mmol), T1(< 96 mmol/L) was associated with higher risks of all-cause mortality (HR, 2.59; 95% CI, 1.55–4.34) and cardiovascular mortality (HR, 3.33; 95% CI, 1.28–8.66). Limitations Observational design with potential residual confounding. Serum chloride and covariates were measured only at registry enrollment. Serum bicarbonate was unavailable. Generalizability may be limited. Conclusions In maintenance PD patients, lower serum chloride concentration was independently associated with increased all-cause and cardiovascular mortality risks, suggesting serum chloride may be a useful marker for risk assessment. Plain-Language Summary Chloride is a common blood electrolyte, but it has received less attention than sodium in kidney research. Recent studies suggest that low serum chloride may be linked to worse outcomes in people with kidney disease, but this has not been well studied in patients continuing peritoneal dialysis. In this study, we used data from a multicenter dialysis registry in Japan to examine whether serum chloride is related to survival in patients continuing peritoneal dialysis. We found that patients with lower serum chloride had a higher risk of death, including from cardiovascular causes. These results suggest that serum chloride may be a simple and widely available marker that could help identify patients on peritoneal dialysis who may benefit from closer monitoring.