Prognostic value of hypochloremia versus hyponatremia among patients with chronic kidney disease—a retrospective cohort study

Abstract

Abstract Background Serum chloride (Cl) levels confer better prognostic value than serum sodium (Na) levels among patients with heart failure. Little is known about the relationship between serum Cl levels and clinical outcomes among patients with chronic kidney disease (CKD). Methods This was a retrospective cohort study enrolling patients with Stages G3–G5 CKD who visited the nephrology outpatient department of Osaka University Hospital from April 2005 to December 2014. The main exposure was time-varying serum Cl levels categorized as quartiles. The study outcome was a composite of all-cause death and cardiovascular events. Results A total of 2661 patients with CKD were included in the analysis. During a median follow-up of 4.0 years, 284 deaths and 416 cardiovascular events occurred. Compared with patients in the third Cl quartile, those in the first Cl quartile showed a significantly higher risk of the outcome after adjustment for demographics and clinical factors including time-varying serum Na, serum albumin and bicarbonate levels, and use of diuretics and sodium bicarbonate [hazard ratio (HR) 2.13; 95% confidence interval (CI) 1.20–3.81; P = 0.01] and, additionally, anion gap (HR 2.13; 95% CI 1.26–3.57; P = 0.004). Adding serum Cl levels, but not serum Na levels, to the multivariable model significantly improved net reclassification index (0.335; P < 0.001) and integrated discrimination improvement (0.0113; P = 0.01). Conclusions Lower serum Cl levels are an independent predictor of death and cardiovascular events. The incremental prognostic value of Cl was superior to that of Na in patients with CKD.