Cross-reaction of propyl and butyl alcohol glucuronides with an ethyl glucuronide enzyme immunoassay

Background: Ethyl glucuronide (EtG) in urine is considered a marker of recent alcohol consumption. Using immunoassays for EtG screening without confirmatory analysis bears a risk of getting false-positives as shown for trichloroethyl glucuronide from chloral hydrate medication and 1-propyl glucuronide from propanol-based hand disinfection. The aim of the study was to check whether glucuronides of frequently used aliphatic short chain alcohols aside from EtG and 1-propyl glucuronide can cross-react with the DRI (R) Ethyl Glucuronide Assay. Methods: Aliquots of EtG-free urine were individually spiked with methyl beta-D-glucuronide, 1-propyl beta-D-glucuronide, 2-propyl beta-D-glucuronide, 1-butyl beta-D-glucuronide, 2-butyl beta-D-glucuronide, and tertbutyl beta-D-glucuronide. To check the response rate of the DRI (R) Ethyl Glucuronide Assay to its target analyte, EtG was also added to a native EtG-free urine sample. The spiked alcohol glucuronide concentrations (seven levels up to 10 mg/L) and the DRI (R) Ethyl Glucuronide Assay results were evaluated by Passing-Bablok regression analysis. The 95% confidence interval ranges for the slope of the regression function were considered a measure of cross-reaction of the individual alcohol glucuronides with the enzyme immunoassay. Results: 2-Propyl glucuronide showed a cross-reactivity of 69-84% at the 95% probability level, methyl glucuronide, 1- propyl glucuronide, and 1-and 2-butyl glucuronide of 4-9%, and tert-butyl glucuronide almost no cross-reactivity. The response rate for EtG was 87-94% at the 95% probability level. Conclusion: The DRI (R) Ethyl Glucuronide Assay shows cross-reaction rates with aliphatic short chain alcohol glucuronides aside from EtG which bear a risk of getting false-positives regarding ethanol consumption. Mass spectrometric detection of EtG is mandatory for confirmation of positive immunological EtG screenings. (C) 2014 Elsevier Ireland Ltd. All rights reserved.