Hours Since Last Drink Is Associated With Multiple Urine Ethyl Glucuronide Cutoffs Among Individuals With Alcohol Use...

Ethyl glucuronide in urine (uEtG) is a biomarker that objectively detects alcohol consumption. However, what uEtG values represent regarding the last drinking event remains unclear. This study investigated whether the recency or amount consumed at the last event are associated with multiple uEtG cutoffs indicative of light to heavy drinking. Adults (n = 349) recruited for an alcohol use disorder clinical trial submitted urine samples and self-reported alcohol measures at baseline and twice weekly during a 4-week observation period prior to treatment. The ThermoFisher DRI immunoassay was used to quantify uEtG levels (0-2000 ng/mL). Self-report measures included the number of hours since last drink (Hours), number of standard drinks at that event (Amount), and ratios of these measures (Hours:Amount and Amount:Hours). Three uEtG cutoffs were assessed (100, 500, and 2000 ng/mL) and generalized linear mixed modeling applied to compare self-report measures below versus above each uEtG cutoff. A total of 1676 uEtG samples with self-reported data were included. Comparisons across cutoffs were significant for Hours (p < 0.001), while Amount was only significant at the 2000 ng/mL cutoff (p = 0.001). Hours also had the strongest association with uEtG results across cutoffs (pseudo-R² range = 0.474-0.530). Higher uEtG results indicated more recent drinking, rather than higher levels of alcohol consumption, and the period of detection of uEtG was shorter than previously reported. Even at the low threshold of 100 ng/mL, uEtG was best conceptualized as a measure of alcohol consumption in the prior 24 h, with higher uEtG levels being associated with fewer hours since last drink.