Verified answer

The 500 ng/ml cut-off is used by most clinics and criminal justice agencies it eliminates the possibility of most "innocent positives" due to inadvertent alcohol exposure.

Ethyl Glucuronide (EtG) is a direct metabolite of beverage alcohol (ethanol). Its presence in urine may be used to detect recent alcohol consumption, even after ethanol is no longer measurable. The presence of EtG in urine is a definitive indicator that alcohol was ingested.

Tests show that “incidental exposure” to the chronic use of food product (vanilla extract), hygiene products, mouthwash, or OTC medications (cough syrups) can produce EtG concentrations in excess of 100 ng/mL. However, if measurable ethanol is detected (greater than .04 gm%) in the urine, and EtG is also detected in excess of 250 ng/mL, then this is very strong evidence that beverage alcohol was consumed.