Discrepancy in chloride measurement with decreasing bicarbonate concentrations

Background: Accurate chloride measurement is important in critically ill patients. Methods: Chloride concentration measured simultaneously between the central laboratory (indirect ion-selective electrode) and blood gas analysis (direct ion-selective electrode) were compared. Results: We report a discrepancy with chloride measurement between the central laboratory and blood gas analysis at low bicarbonate levels. Conclusions: Caution should be applied while interpreting the chloride concentration when indirect ion-selective electrode methodology is used, especially in the setting of low serum bicarbonate levels.