Widely-Used EtG Test for Confirming Alcohol Abstinence

A widely-used urine test, the EtG (ethyl glucuronide) test is a biomarker screening that detects the presence of ethyl glucuronide, a breakdown product of ethanol, in urine samples. It can also detect the presence of EtG in your blood, hair, and nails, although the urine test is the most widely used. 

The purpose of an EtG test is to document​ required alcohol abstinence, but the urine test can only measure alcohol intake within the last one to three days.

You may be surprised to learn that after consuming alcohol, only about 0.5 percent to 1.5 percent of it is eliminated in your urine, and this is after undergoing a process called glucuronidation to form the breakdown product, EtG. 

Even so, the EtG test is quite sensitive and can detect even low levels of alcohol. In fact, the EtG urine test can technically detect alcohol in the urine up to five days after consumption. That said, in studies of participants without alcohol use disorders, EtG has been detected in urine samples for up to 80 hours after heavy alcohol exposure, so up to three days is probably a more reasonable estimate.

Due to the common use of EtG to confirm recent alcohol abstinence, the Substance Abuse and Mental Health Services Administration (SAMHSA) has suggested the following cutoff values, based on scientific research:

"High" positive EtG test (for example, >1,000ng/mL) may indicate:

• Heavy drinking on the same day or the previous day 
• Light drinking on the same day as the test

"Low" positive EtG test (for example, 500 to 1,000ng/mL) may indicate:

• Heavy drinking within the last one to three days
• Light drinking within the last 24 hours
• Recent intense exposure to environmental products containing alcohol (within the last 24 hours)

"Very Low" positive EtG test (for example, 100 to 500 ng/mL) may indicate:

• Heavy drinking within the last one to three days
• Light drinking within the last 12 to 36 hours
• Recent exposure to environmental products containing alcohol

A problem with the EtG test is that it can produce a positive test from the mere exposure to alcohol that is present in many daily use products. Examples of environmental or home products that contain alcohol include:

• Foods prepared with or flavored with alcohol
• Cleaning products
• Mouthwashes
• Breath sprays
• Hand sanitizers
• Hygiene products like antiperspirant
• Aftershave
• Cosmetics
• Hair dye

In fact, there are hundreds of household products that contain ethanol, according to the National Library of Health's Household Products Database, and this could possibly lead to a false positive on the EtG urine test.

In addition, SAMHSA lists EtG as a "highly" sensitive and specific alcohol biomarker. As a sensitive test, this means that the EtG test accurately at least 70 percent or more of the time detects a person who recently consumed alcohol. One recent study showed that for moderate to heavy drinking, this number jumps to 85 percent. As a specific test, this means that the EtG accurately at least 70 percent or more of the time identifies people who did not recently consume alcohol. For moderate to heavy drinking, the above-mentioned showed that the specificity is 89 percent.

The test for EtG is widely used to detect alcohol abstinence in situations that do not allow drinking, including:

• Alcohol treatment programs
• A DUI or DWI program
• Liver transplant patients
• Schools or the military
• Professional monitoring programs (for example, airline pilots, healthcare professionals, attorneys)
• Court cases (for example, child custody)
• Probation programs

It's important to note that the EtG test is not recommended for use in workplace testing programs as it does not measure current impairment from alcohol.

All in all, the EtG test is considered a highly useful test for detecting recent alcohol consumption. But like any test, there is the possibility for a false positive. This is why a positive test should be confirmed either with another test or with verification from the person that he or she did indeed drink alcohol. 

Hopefully, as the research on EtG and other alcohol biomarkers unfolds, a clearer cutoff value can be made in order to distinguish between true alcohol use and exposure to alcohol in environmental products.