With alcohol being the most widely abused drug, having a reliable way to test for it is important.
Pat Pizzo, Director of Toxicology at Alere Toxicology, presented a webinar Feb. 28 entitled; EtG & EtS: A New Way to Look at Alcohol Testing to explain the ins and outs of EtG and EtS testing.
Unlike more traditional forms of alcohol testing, which test for ethanol, EtG tests look at the level of Ethyl Glucuronide.
Pizzo said the biggest advantage of testing for EtG as opposed to ethanol is that EtG breaks down or metabolizes without oxidizing, creating an analyte that can be measured for up to four or five days after alcohol consumption compared to only eight to twelve hours after consumption when testing for ethanol. EtG can also be detected in urine, plasma, hair and body tissue.
Ethyl sulfate (EtS), a direct, bio-marker of alcohol ingestion that is not susceptible to degradation by bacteria hydrolysis, is tested in conjunction with EtG for confirmation purposes, Pizzo said.
Testing for EtG
At the moment, testing for EtG is done exclusively via laboratory screening, as there is no instant tests available.
EtG, in conjunction with ethyl sulfate (EtS) is a scientifically accepted biomarker, Pizzo added, to show exposure to alcohol. It’s stable in urine, meaning that if you must keep specimens for extended periods, fermentation of the specimens won’t give you a false positive.
Disadvantages of EtG testing
EtG/EtS testing does come with some disadvantages, though, Pizzo acknowledged, the main one being false positives from donors who have not consumed alcoholic beverages but have been incidentally exposed to alcohol through some other means, like cough syrup; mouth wash or hand sanitizer.
Scientific studies have found that EtG will show up in urine samples from people who regularly use things like mouth wash and hand sanitizer, but these levels will almost always be below the commonly accepted cut off limit of 500 nanograms per milliliter (ng/ml).
False negative and false positive results have also been noted in test results due to bacterial contamination from the presence of E. Coli bacteria but testing for EtS in addition to EtG, Pizzo said, has proven effective in avoiding most false positives and false negatives and provides analytical results that are acceptable in court.
Interpreting test results
It is important to consider not only the cutoff levels when interpreting results for EtG tests, Pizzo said, but also the normalization of results and the use of both EtG and EtS for confirmation of results.
In addition to the commonly accepted cutoff level for EtG of greater than or equal to 500 ng/ml the commonly accepted cutoff level for testing for EtS is 25 ng/ml.
If cutoff levels of below 500 ng/ml for EtG are used, the test runs the risk of giving false positives for samples of individuals who may have experienced incidental exposure to alcohol through items like hand sanitizers and food made with alcohol, as mentioned above.
If an EtG test shows a level of greater than 500 ng/ml, however, that is considered as a result that is consistent with the recent ingestion of alcohol.
When testing a urine sample for EtG and EtS, it is important to not just look at the EtG level, Pizzo said, but to calculate the normalized level because that’s the only way you can account for possible dilution of the sample.
Normalization is the consideration of how the dilution or concentration of a urine sample impacts the result of a drug screen test. Drugs are measured in ng/ml and the more dilute the urine, the lower the drug concentration, she explained.
Normalization is done by using a calculation that requires not only the EtG levels of the sample, but also the levels of creatinine, a product created by the breakdown of creatine phosphate in muscle that is usually produced at a constant rate by the body.
This normalization calculation helps testers recognize when a drug user who is being monitored by giving samples at set intervals is reusing the drug or if the user’s body is still processing drugs from older usage but has not reused, referred to as residual elimination.
It is important for corporate alcohol testing to specifically mention testing for both EtG and EtS, in your corporate drug testing policy, Pizzo noted, and educate your employees on the risk of incidental alcohol exposure. You should also give them a list of things that could expose them to alcohol and also notify them that it is only a partial listing, as opposed to a complete listing.
As useful as EtG and EtS testing are for detecting recent alcohol usage, though, Pizzo noted, these tests are not meant to prove impairment from alcohol or whether someone is currently under the influence of alcohol. The only tests that can be used to determine impairment are blood, saliva and breath based on ethanol levels in those substances. In California, urine tests can be used to prove impairment based on ethanol levels.
Aside from workplaces, EtG and EtS testing is done in the criminal justice system and in rehabilitation programs and is especially useful in court cases involving driving under the influence (DUI), custody battles and when determining a cause of death.