How good are clinical chemistry laboratories at analysing ethylene glycol?

The results of an external proficiency test of clinical chemistry laboratories in Sweden when the target analyte was ethylene glycol (EG) are presented. Specimens of plasma were spiked with EG (10% w/v) to give assigned concentrations ranging from 5 to 50 mmol/L. Over a period of 6 years, two control specimens of plasma were sent for analysis on 21 occasions to between 14 and 20 participating laboratories as a declared proficiency trial. The analytical precision between and within laboratories was determined by spiking the plasma specimens with the same concentration of EG so that the results reported back could be considered a duplicate determination. On one occasion propylene glycol (PG) was substituted for EG without informing the participants. The standard deviation (SD) within laboratories expressed as the coefficient of variation (CV) was 4.5% compared with 11.4% between laboratories. Results reported by laboratories using gas chromatography (GC) were in good agreement with those when an enzymatic method was used. The between-laboratory SD increased with concentration of EG in the specimen and at a mean concentration of 18 mmol/L, the pooled SD was 4.11 mmol/L (CV = 23%). Four laboratories reported finding EG in plasma when PG was the diol present; three laboratories used an enzymatic method and one used GC. Clinical laboratories that provide a toxicology service should regularly participate in external quality assurance schemes that include low-molecular-weight alcohols such as EG. Efforts should be made to standardize the analytical methods used for toxicological analysis.

Ethylene glycol poisoning: toxicokinetic and analytical factors affecting laboratory diagnosis

Ethylene glycol poisoning is an important toxicological problem in medical practice because early diagnosis and treatment can prevent considerable morbidity and mortality. When ingested in the form of antifreeze or other automotive products, ethylene glycol results in central nervous system depression, cardiopulmonary compromise, and renal insufficiency. Metabolism of ethylene glycol to organic acids is required for metabolic derangement and organ damage. Laboratory features of ethylene glycol poisoning include increased anion gap metabolic acidosis, increased osmolal gap, calcium oxalate crystalluria, and detectable ethylene glycol in serum. This Case Conference integrates discussion of the toxicokinetic and analytical variables that affect the laboratory diagnosis of ethylene glycol intoxication.

Serum ethylene glycol by high-performance liquid chromatography

A high-performance liquid chromatography procedure for detection and quantitation of ethylene glycol in serum is described. Ethylene glycol and internal standard are derivatized with benzoyl chloride under alkaline conditions, purified by solid-phase extraction and analyzed by HPLC with UV detection. Analytical recovery of ethylene glycol ranges between 96 and 103%. The calibration curve is linear from 20 to 2000 mg/l. The limits of detection and quantitation are 10 and 20 mg/l, respectively. Assay imprecision is 4.8% or less. The assay is free from common interferences and provides increased sensitivity, improved precision and extended linearity.

Simultaneous determination of ethylene glycol, propylene glycol, 1,3-butylene glycol and 2,3-butylene glycol in human serum and urine by wide-bore column gas chromatography

A method has been developed for the separation and measurement of ethylene glycol and three other glycols (propylene glycol, 1,3-butylene glycol and 2,3-butylene glycol) in biological samples by wide-bore column gas chromatography with a flame ionization detector. The method used 1,3-propylene glycol (1,3-propanediol) as an internal standard. The method was linear at least from 2 to 1000 micrograms/ml, with a detection limit of 1 microgram/ml. Analytical recoveries were 89-98% for the different concentrations. Precision studies showed coefficients of variation of 1.5-7.7% for the different concentrations. The assay was applied to the analysis of biological samples from two patients who had ingested ethylene glycol and/or other glycols in a suicide attempt.