All you need to know about EtG & EtS Testing for Alcohol Consumption
With alcohol being the most widely abused drug — because of its legal status — being able to reliably test for its presence in people is important in situations where alcohol use is prohibited (in certain occupational situations or in individuals who have been prohibited from consuming alcohol, for example).
Alcohol is the only drug in the United States for which both state and federal governments have established levels of intoxication for being under the influence. No other drug has had these levels established by a governing body in the States.
It has been estimated that alcohol abuse costs the American economy $150 billion and that 80% of child abuse, domestic assaults and violent crimes have been committed under the influence of alcohol. Also, more than 1 million Americans have an alcohol addiction or abuse problem and more than 110 million emergency room visits per year are related to alcohol.
EtG vs Ethanol testing
With more traditional forms of alcohol testing, like breath, saliva or standard urine testing, it’s ethanol that is tested for. However, with EtG testing, it is Ethyl Glucuronide that is tested for.
An 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 a much longer period than ethanol can be measured for.
EtG is a direct, non-volatile, water soluble, metabolite of ethanol. It’s a highly sensitive and specific bio-marker and can be detected anywhere from four to five days after alcohol consumption as opposed to eight to 12 hours when testing for ethanol, making it useful for situations where a person needs to be monitored on a continuous basis. It can also be detected in urine, plasma, hair and body tissue.
Ethyl sulfate (EtS) is tested in conjunction with EtG for confirmation purposes. EtS is a direct, bio-marker of alcohol ingestion that is not susceptible to degradation by bacteria hydrolysis.
Testing for EtG
Testing for EtG is done exclusively via laboratory screening, as there is no instant tests available for it at the moment. Confirmation of results is done by Liquid Chromatography - Mass Spectrometry and Liquid Chromatography - Tandem Mass Spectrometry (LC/MS/MS, which is the most sensitive and, therefore, preferred method); gas chromatography-mass spectrometry (GC/MS) or Liquid Chromatography - Mass Spectrometry (LC/MS).
EtG, in conjunction with EtS, is a scientifically accepted biomarker to show exposure to alcohol. It’s non-volatile, meaning it’s stable in urine and that means that if you have to keep specimens for extended periods, you won’t get a false positive due to fermentation and it doesn’t show up in the urine of sample donors that have not been exposed to ethanol.
Disadvantages of EtG testing
EtG testing alone does have some disadvantages, 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.
Sources of alcohol that lead to incidental exposure include:
- cough syrup
- mouth wash
- insect repellant
- hand sanitizers
- non-alcoholic beer
- some kinds of canned or bottled iced tea
- perfumes/colognes & body sprays
- food products made or cooked with alcohol
Many of these products contain minute traces of alcohol but could prove problematic for people who are in programs where there is zero tolerance for alcohol.
Scientific studies have found that EtG will show up in urine samples from people who regularly use things like mouth wash and hand sanitizer, however, 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.
Avoiding these false negatives is why it is important to test for EtS at the same time as EtG. The inclusion of testing for EtS in conjunction with EtG has proven effective in avoiding most false positives and false negatives and provides analytical results that are acceptable in court.
Interpreting test results
When interpreting results for alcohol EtG tests, it’s important to consider the cutoff levels, normalization of results and the use of both EtG and EtS for confirmation results.
As previously mentioned, a commonly accepted cutoff level for EtG is greater than or equal to 500 ng/ml and a commonly accepted cutoff level for testing for EtS is 25 ng/ml.
If cutoff levels of below 500 ng/ml 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.
If an EtG test shows a level of greater than 500 ng/ml, 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, 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.
When testing is being done to monitor a person for alcohol intake, normalization is used to determine whether the EtG that shows up in a urine sample represents new use of alcohol or whether it represents older consumption that has not yet been eliminated from the body.
It is done by using a calculation that requires not only the EtG levels of the sample, but also the levels of creatinine, which is a product created by the breakdown of creatine phosphate in muscle, usually produced at a constant rate by the body.
Creatinine levels, on average, should be around 190 milligrams per deciliter (mg/dl) for males and 140 mg/dl for females. Testers use the range of 100 - 200 mg/dl to judge whether creatinine levels are normal for a sample.
Testers also compare the specific gravity of the sample to water, specific gravity being the ratio of the density of a substance (urine) to the density (mass of the same unit volume) of a reference substance (water). The normal range of specific gravity for urine compared to water is 1.010 - 1.025.
The calculation for getting a normalized reading is done by taking the amount of drug in the sample divided by the amount of creatinine in the sample and multiplying that by 100, which gives you nanograms of drug per milligram of creatinine. The results of this calculation enable testers to determine if the sample has been diluted (by excessive water consumption, for example).
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.
For corporate alcohol testing, it is important to specifically mention testing for both EtG and EtS in your corporate drug testing policy and educate your employees on the risk of incidental alcohol exposure and 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.
EtG and EtS testing will likely have employers seeing more positive test results than if they were to test for ethanol metabolites alone because of the longer detection window of EtG (4-5 days as opposed to 8-12 hours).
EtG is 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, breath and -- only in California -- urine, based on ethanol levels.
Aside from workplaces, EtG and EtS testing is done in the criminal justice system and in rehabilitation programs.
Source; Webinar EtG & EtS: A New Way to Look at Alcohol Testing by Pat Pizzo, Dir. of Toxicology at Alere Toxicology