Potential Inaccuracies in Chloride Measurements in Patients with Severe Metabolic Acidosis

Abstract

Background. To address the cause(s) of the significant differences in chloride (Cl-) concentrations between point-of-care blood gas analyzers and central laboratory analyzers.Methods. Cl-concentrations measured simultaneously by a blood gas analyzer (ABL800 FLEX) and a central laboratory analyzer (Hitachi7600) were collected in patients with severe acidemia (pH<7.20) (n=32) and were examined for correlations between differences in Cl-and factors associated with the acid-base status. Cl-concentrations were measured with both analyzers for samples with different concentrations of lactate, inorganic phosphate, or bicarbonate (HCO3   −).Results. The differences in Cl-concentrations were correlated withHCO3   −concentrations (r=0.72,P<0.0001) and anion gap (r=0.69,P<0.0001). Only the addition ofHCO3   −proportionately increased Cl-levels measured by a Hitachi7600, but it did not affect those measured by an ABL800FLEX.Conclusion. Cl-measurements with some analyzers may be influenced byHCO3   −concentrations, which could result in the observed discrepancies.