The detection of alcohol consumption has evolved beyond traditional breath and blood tests, leading to the use of biomarkers that offer a longer detection window. Ethyl Glucuronide (EtG) is a non-volatile compound and a widely accepted indicator of recent alcohol intake. This biomarker allows for testing in various specimens, moving past the short detection period of ethanol itself. Using oral fluid for EtG testing offers distinct advantages in collection.
Understanding Ethyl Glucuronide (EtG)
Ethyl Glucuronide is a direct, minor metabolite of ethanol, the alcohol found in beverages. When a person consumes alcohol, the body’s primary metabolic pathway breaks down most of the ethanol in the liver through oxidation. A small portion of the ethanol, however, is processed through a secondary pathway known as conjugation.
In this process, the enzyme UDP-glucuronosyltransferase catalyzes the reaction between ethanol and glucuronic acid. This reaction creates the stable compound EtG, which is then excreted from the body. Unlike ethanol, which is rapidly eliminated from the bloodstream and breath, EtG remains in the body for a much longer time.
The Feasibility of EtG Testing in Saliva
Testing for Ethyl Glucuronide in oral fluid (saliva) is possible. The metabolite is transferred from the systemic circulation into the oral cavity through passive diffusion. Although EtG is found in saliva, concentrations are significantly lower than those found in urine or blood.
Saliva samples are collected using a simple, non-invasive device or swab. This method offers a practical advantage because the collection process is easily observed, reducing the potential for sample adulteration or substitution. The oral fluid sample is sent to a laboratory for analysis. The most common method for quantitative analysis is Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), which is necessary to accurately measure the low concentrations of EtG present in the oral fluid.
Saliva EtG Detection Windows and Accuracy
The utility of saliva EtG testing is defined by its detection window, which is shorter than that of the standard urine test. While EtG can be detectable in urine for up to 80 hours after consumption, the window in saliva is significantly reduced, typically lasting around 12 to 24 hours post-consumption. Studies show that for a high dose of ethanol, the median detection time for EtG in oral fluid can be as short as 11.5 hours.
This shorter timeframe means the saliva test provides limited additional value over simply testing for ethanol itself, which is rapidly cleared. The accuracy and sensitivity of saliva testing depend on the low levels of EtG present. The concentration of EtG in oral fluid can be less than one percent of the concentration found in blood, making laboratory measurement challenging. Residual alcohol from non-beverage sources, such as mouthwash, can also influence the results, requiring careful collection protocols.