Pseudohypobicarbonatemia: Discordant Bicarbonate Values in Serum and Arterial Samples

Pseudohypobicarbonatemia, a falsely low serum bicarbonate level due to laboratory interference, is an underrecognized condition in clinical practice. We describe a 30-year-old patient whose metabolic panels repeatedly suggested a high-anion gap metabolic acidosis, while arterial blood gas testing showed a normal bicarbonate level, ultimately attributable to severe hypertriglyceridemia. Lipid interference is well documented in the literature. Our laboratory analyzer is designed to flag lipemic specimens using a lipemia index; however, this sample was not flagged despite triglyceride concentrations above the usual cutoff. We propose that variability in the patient's specimen, which contained a heterogeneous mixture of lipid particles, altered light scattering across measurements and produced a falsely low lipemia index. Awareness of pseudohypobicarbonatemia can help clinicians promptly recognize reversible causes of lipemia or other forms of analytical interference.