Ethylene glycol: Evidence of glucuronidation in vivo shown by analysis of clinical toxicology samples

In the search for improved laboratory methods for the diagnosis of ethylene glycol poisoning, the in vivo formation of a glucuronide metabolite of ethylene glycol was hypothesized. Chemically pure standards of the β-O-glucuronide of ethylene glycol (EG-GLUC) and a deuterated analog (d4 -EG-GLUC) were synthesized. A high-performance liquid chromatography and tandem mass spectrometry method for determination of EG-GLUC in serum after ultrafiltration was validated. Inter-assay precision (%RSD) was 3.9% to 15.1% and inter-assay %bias was -2.8% to 12.2%. The measuring range was 2-100 μmol/L (0.48-24 mg/L). Specificity testing showed no endogenous amounts in routine clinical samples (n = 40). The method was used to analyze authentic, clinical serum samples (n = 31) from patients intoxicated with ethylene glycol. EG-GLUC was quantified in 15 of these samples, with a mean concentration of 6.5 μmol/L (1.6 mg/L), ranging from 2.3 to 15.6 μmol/L (0.55 to 3.7 mg/L). In five samples, EG-GLUC was detected below the limit of quantification (2 μmol/L) and it was below the limit of detection in 11 samples (1 μmol/L). Compared to the millimolar concentrations of ethylene glycol present in blood after intoxications and potentially available for conjugation, the concentrations of EG-GLUC found in clinical serum samples are very low, but comparable to concentrations of ethyl glucuronide after medium dose ethanol intake. In theory, EG-GLUC has a potential value as a biomarker for ethylene glycol intake, but the pharmacokinetic properties, in vivo/vitro stability and the biosynthetic pathways of EG-GLUC must be further studied in a larger number of patients and other biological matrices.