title: An enzymatic assay for the detection of glycolic acid in serum as a marker of ethylene glycol poisoning.
abstract: BACKGROUND
  Ingestion of ethylene glycol is a relatively rare event but one with potentially lethal consequences. Early diagnosis and appropriate treatment are essential. However, diagnosis of poisoning can only be confirmed definitively by the measurement of ethylene glycol and/or its metabolites, usually performed by gas chromatographic methods. These methods are complex, requiring specialized equipment and expertise, and are often not available on an emergency basis.
  
  
  METHODS
  A quick, simple, and inexpensive enzymatic assay has been developed to detect glycolic acid, the major metabolite of ethylene glycol and the main cause of the resulting metabolic acidosis. In this assay, glycolic acid is converted to glyoxylic acid by glycolate oxidase, with the production of hydrogen peroxide, which is converted to a quinoneimine dye for spectrophotometric detection.
  
  
  RESULTS
  The assay has a functional sensitivity of 26 mg/L and coefficients of variation less than 13% (interassay) and less than 10% (intra-assay). No significant interference was observed for a range of compounds, and a comparison with a gas chromatography-mass spectrometry method gave clinical sensitivity of 86% and clinical specificity of 92%. Stability of enzyme solutions was increased by the use of an alternative buffer, in which greater than 90% of the original activity was retained after storage at -20°C.
  
  
  CONCLUSIONS
  As ethylene glycol poisoning is a medical emergency, there is a need for a screening test to minimize delays in diagnosis. The assay we describe is a simple and effective way to detect ethylene glycol poisoning, enabling earlier initiation of appropriate therapy and improving patient outcomes.
authors.affiliation: Department of Clinical Biochemistry, Aintree University Hospital, Liverpool, UK.
authors.forename: Sally L
authors.initials: SL
authors.lastname: Hanton
authors.forename: Ian D
authors.initials: ID
authors.lastname: Watson
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D004355:Drug Stability; D004356:Drug Storage; D019855:Ethylene Glycol / Q000378:metabolism / Q000506:poisoning*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006016:Glycolates / Q000097:blood*; D006801:Humans; D006861:Hydrogen Peroxide / Q000032:analysis; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods*
chemical_list: D006016:Glycolates; C031149:glycolic acid; D006861:Hydrogen Peroxide; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase; D019855:Ethylene Glycol