Relationship Between Serum Total Carbon Dioxide Concentration and Bicarbonate Concentration in Patients Undergoing Peritoneal Dialysis.

Abstract

BackgroundFew studies have assessed the relationship between serum total carbon dioxide (CO2) and bicarbonate ion (HCO3−) concentration in patients undergoing peritoneal dialysis. We determined the agreement between serum total CO2 and HCO3− concentration and the diagnostic accuracy of serum total CO2 for the prediction of low (HCO3− <24 mEq/L) and high (HCO3− ≥24 mEq/L) bicarbonate concentrations in patients on peritoneal dialysis.MethodsWe collected 245 samples of venous blood from 51 patients on peritoneal dialysis. Independent factors that correlated with the HCO3− concentration were analyzed using multiple linear regression analysis. The diagnostic accuracy of serum total CO2 was evaluated by receiver operating characteristic (ROC) curve analysis and a 2×2 table. Agreement between serum total CO2 and HCO3− concentration was assessed by Bland-Altman analysis.ResultsSerum total CO2 was independently correlated with HCO3− concentration (β = 0.354, p < 0.001). The area under the curve of serum total CO2 for the identification of low and high bicarbonate concentrations was 0.909. The diagnostic accuracy of serum total CO2 for the prediction of low and high bicarbonate concentrations was: sensitivity, 91.5%; specificity, 74.7%; positive predictive value, 53.5%; negative predictive value, 96.5%; and accuracy, 78.8%. Bland-Altman analysis showed a moderate agreement between serum total CO2 and HCO3− concentration.ConclusionSerum total CO2 correlated closely with the HCO3− concentration in patients undergoing peritoneal dialysis. Serum total CO2 might be useful for predicting low and high bicarbonate in peritoneal dialysis patients.