False-positive ethyl glucuronide immunoassay screening caused by a propyl alcohol-based hand sanitizer

Abstract

BackgroundUrine ethyl glucuronide (EtG) is considered as a specific marker of recent ethanol consumption. We describe false-positive DRI® EIA EtG enzyme immunoassay results caused by propyl glucuronides in urine after using a propanol-based hand sanitizer. MethodsEtG screening was done with the DRI® EIA EtG assay (Microgenics), using a cut-off of 0.5mg/L as recommended by the manufacturer and of 0.1mg/L as demanded by the German Regulations for Reissuing Drivers Licenses. Confirmatory EtG analysis was done with the ClinMass® EtG LC–MS/MS testkit (Recipe), extended by the mass transitions 235.1→75.1, 235.1→85.1, and 235.1→113.1 for the detection of the 1- and 2-propyl glucuronides. Self-experiments were done by staff members of our lab (n=7), using 3mL Sterillium® Classic Pure (30g/100g 1-propanol and 45g/100g 2-propanol) for hand sanitation every quarter of an hour for 8h according to DIN EN 1500:2011-05 with and without an exhauster and by passive inhalation of the sanitizer vapor. Spot urine samples were taken immediately before and up to 24h after the first sanitizer use. ResultsFalse-positive immunoassay results of up to 4mg/L or 2.3mg/g creatinine were obtained after normal use of the sanitizer and also after passive inhalation of the sanitizer vapor (up to 0.89mg/L or 0.61mg/g). Immunoassay results were positive even after 4-fold use of the sanitizer (up to 0.14mg/L or 0.38mg/g) and up to 6h after the last sanitizer contact (maximum 0.63mg/L and 0.33mg/g for sanitizer users and 0.25mg/g after passive inhalation). Spiking of EtG-free urine with 1-propyl glucuronide (Athena Environmental Sciences) between 0.05 and 10mg/L clearly demonstrated a cross reaction of the immunoassay of approx. 10% as compared to EtG. LC–MS/MS of urines with a positive immunoassay EtG result did not show EtG signals, but distinct signals of 1-propyl glucuronide (n-propyl glucuronide) and 2-propyl glucuronide (iso-propyl glucuronide). An exhauster effectively prevented the inhalation of the sanitizer vapor, the formation of propyl glucuronides and thus false-positive DRI® EIA EtG screening results, proving that propyl alcohols are almost exclusively taken up by respiration. ConclusionsThe widespread use of propanol-containing products such as hand sanitizers may lead to sufficient uptake of propyl alcohols and excretion of significant amounts of propyl glucuronides to yield false-positive DRI® EIA EtG screening results. Thus, positive EtG immunoassay results have to be controlled by mass-spectrometry, in clinical cases at least if ethanol intake is denied by the patient.