A Case of Profound Hypertriglyceridemia Causing Pseudohypobicarbonatemia

Abstract

The light-scattering effect of hypertriglyceridemia may interfere with the photometric analysis of the electrolytes, leading to errors in laboratory values. We present a case of erroneously low bicarbonate levels due to the presence of severe hypertriglyceridemia. A 49-year-old male was admitted for knee cellulitis. A comprehensive metabolic panel showed very low bicarbonate of <5 mmol/L, and an elevated anion gap of 26 mmol/L. The lactic acid, salicylic acid, ethanol, and methanol levels were normal. The lipid panel showed a remarkably high triglyceride level of 4846 mg/dL. An arterial blood gas (ABG) showed a normal pH of 7.39 and a bicarbonate level of 28 mmol/L, which was inconsistent with the metabolic acidosis seen in the blood test. The discrepancy between acidosis seen in the metabolic panel and ABG was explained by a lab error in the measured bicarbonate levels, which occurs in the presence of elevated triglyceride levels. Most laboratories use either an enzymatic/ photometric or an indirect ion-selective electrode method to measure bicarbonate. Hyperlipidemia interferes with photometric analysis due to its light-scattering effect. An ABG analyzer uses a direct ion-selective electrode method that is free of the errors of a photometric analyzer. Knowing about conditions like hypertriglyceridemia, which can interfere with the measurement of electrolytes, is important in everyday clinical medicine, as it can prevent unnecessary investigation and intervention.

Pseudo-Hypobicarbonatemia in Patients With Hypertriglyceridemia

“…Hypobicarbonatemia with an elevated anion gap on a metabolic panel is frequently the initial marker of a life-threatening condition such as diabetic ketoacidosis in a patient with epigastric pain [1].…”

“…The two commonly used means of measuring bicarbonate levels are direct measurement from a metabolic panel and calculated measurement from ABG [1]. Direct measurement via a metabolic panel utilizes the total CO 2 as an accurate surrogate for the bicarbonate level as it is 95% bicarbonate while dissolved CO 2 and carbonic acid constitute the remaining ~5% [1]. For measuring total CO 2 , automated chemistry analyzers use either an indirect ion-selective electrode or the enzymatic/spectro-photometric method [1].…”

“…Direct measurement via a metabolic panel utilizes the total CO 2 as an accurate surrogate for the bicarbonate level as it is 95% bicarbonate while dissolved CO 2 and carbonic acid constitute the remaining ~5% [1]. For measuring total CO 2 , automated chemistry analyzers use either an indirect ion-selective electrode or the enzymatic/spectro-photometric method [1]. With the spectro-photometric method, certain wavelengths of light get absorbed based on the specific properties of the analyte [1].…”

“…Hypobicarbonatemia with an elevated anion gap on a metabolic panel is frequently the initial marker of a life-threatening condition such as diabetic ketoacidosis in a patient with epigastric pain [1]. The two commonly used means of measuring bicarbonate levels are direct measurement from a metabolic panel and calculated measurement from arterial blood gas (ABG) [1].…”

“…Hypobicarbonatemia with an elevated anion gap on a metabolic panel is frequently the initial marker of a life-threatening condition such as diabetic ketoacidosis in a patient with epigastric pain [1]. The two commonly used means of measuring bicarbonate levels are direct measurement from a metabolic panel and calculated measurement from arterial blood gas (ABG) [1]. It was postulated that the light-scattering effect of hyperlipidemia interfered with the enzymatic/spectro-photometric method, resulting in factitious low bicarbonate levels [2].…”