Artifactual elevation of measured plasma L-lactate concentration in the presence of glycolate

Crit Care Med. 1999 Oct;27(10):2177-9. doi: 10.1097/00003246-199910000-00017.

Abstract

Objectives: To determine whether glycolate, a toxic metabolite of ethylene glycol that is chemically similar to lactate, can cause artifactual elevation of measured L-lactate concentrations.

Design: Prospective in vitro study.

Setting: Intensive care unit and chemical pathology laboratory in a university-affiliated hospital.

Subjects: Heparinized normal human blood and four commercially available L-lactate analyzers.

Interventions: Four analyzers were tested, three of which used L-lactate oxidase and one of which used L-lactate dehydrogenase. Glycolic acid (10 g/L) in saline was added to blood in a series of aliquots. Corresponding plasma L-lactate concentrations and blood pH, PCO2, and hemoglobin concentrations were measured and base excess was calculated initially and after the addition of each aliquot. One of the two L-lactate oxidase-type analyzers, which was found to show interference, was then used to measure plasma L-lactate and glucose concentrations in blood with glycolic, oxalic, or formic acid added until the base excess was reduced by >15 mmol/L.

Measurements and main results: Artifactual plasma L-lactate elevations were observed in two analyzers, both of the L-lactate oxidase type. Small concentrations of glycolic acid (causing reductions of base excess of 2-5 mmol/L) were accompanied by artifactual plasma L-lactate elevations of 4-8 mmol/L. Artifactual plasma L-lactate elevations increased with further glycolic acid-induced reductions in base excess. Oxalate and formate did not interfere with plasma L-lactate measurements, and measured plasma glucose concentrations were unaffected by all three acids.

Conclusions: Glycolate causes large artifactual elevations in plasma L-lactate measurements by two analyzers in common use, with potential for misdiagnosis of lactic acidosis in ethylene glycol poisoning. A possible cause of the interference is incomplete specificity of the analytical reagent L-lactate oxidase, allowing cross-reaction with glycolate.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acidosis, Lactic / blood
  • Acidosis, Lactic / chemically induced
  • Acidosis, Lactic / diagnosis
  • Blood Gas Analysis
  • Blood Glucose / metabolism
  • Diagnosis, Differential
  • Ethylene Glycol / poisoning
  • Formates / pharmacology
  • Glycolates / pharmacology*
  • Hemoglobins / metabolism
  • Hospitals, University
  • Humans
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Intensive Care Units
  • Lactic Acid / blood*
  • Mixed Function Oxygenases / pharmacology
  • Oxalic Acid / pharmacology
  • Prospective Studies

Substances

  • Blood Glucose
  • Formates
  • Glycolates
  • Hemoglobins
  • glycolic acid
  • formic acid
  • Lactic Acid
  • Oxalic Acid
  • Mixed Function Oxygenases
  • lactate 2-monooxygenase
  • Ethylene Glycol