Spuriously Low Serum Bicarbonate Levels in Patients With Hyperlipidemia: A Report of 4 Cases

Four patients were recently seen at our institution presenting with severe hypobicarbonatemia and elevated anion gap on serum specimens processed by an autoanalyzer using enzymatic reactions. Arterial blood gas values in each case revealed no significant acid-base disturbance and a marked discordance between arterial blood gas calculated bicarbonate levels and those reported on the basic metabolic panel. All patients had profound hyperlipidemia (triglycerides > 3,500mg/L), and ultracentrifugation of one patient's serum corrected the discordance. Lipid interference with the photometric measurement of light absorbance after enzymatic reaction in the autoanalyzer is thought to be responsible for the low reported bicarbonate values. Use of an indirect ion-specific electrode method for total carbon dioxide analysis would avoid this pitfall. Caution is advised when enzymatic autoanalyzer-calculated laboratory values are used to diagnose acid-base disturbances in patients with severe hyperlipidemia. Physicians involved in the diagnosis of acid-base disorders in hospitalized patients should always be aware of the method used by their chemistry laboratories to determine total carbon dioxide values.