Extended blood ethyl glucuronide persistence after controlled ethanol administration: Implications for...

Delayed blood sampling complicates forensic interpretation in driving-under-the-influence investigations when ethanol concentrations have declined below routine reporting thresholds. Blood ethyl glucuronide (EtG) may provide evidence of recent alcohol exposure, but its late-phase persistence under controlled conditions remains incompletely characterized. This secondary analysis evaluated blood EtG persistence following controlled administration of 1.0 g/kg ethanol in 34 participants using a predefined operational threshold of 0.09 mg/L and sampling through 15 h after completion of drinking. The operational persistence event was defined as the first scheduled sample with EtG < 0.09 mg/L, whereas participants remaining at or above the threshold at 15 h were right-censored. Kaplan-Meier analysis estimated a median operational persistence time of 15 h (95% CI, 14h-not reached). At the final 15-h sampling time, 13 of 34 participants (38%) remained at or above 0.09 mg/L; therefore, the upper boundary of persistence was not observed. Last observed EtG-positive sampling times ranged from 10 to 15 h, and terminal EtG half-lives ranged from 1.4 to 2.9 h. Five forensic cases with blood ethanol concentrations below the laboratory reporting threshold and delayed blood sampling were reviewed descriptively. Incomplete and unverified drinking and clinical histories precluded quantitative comparison with the controlled concentration-time data. These findings provide late-phase blood EtG observations relevant to delayed DUI investigations but do not provide a validated basis for estimating ethanol dose or exact drinking time from a single EtG concentration.