How Reliable Are EtG and EtPa as Markers of Alcohol in Legal Cases?

Bolstering Hair Strand Test Results: Combining EtG and EtPa with PEth

Two of the most commonly used biomarkers for alcohol consumption in hair strand testing are Ethyl Glucuronide (EtG) and Ethyl Palmitate (EtPa). These markers offer an extended window for detecting alcohol use, up to 6 months in head hair.

However, both markers come with specific vulnerabilities that can lead to false positives or negatives, particularly when individuals attempt to manipulate the results or unknowingly expose themselves to certain chemicals. As you'll see, we recommend the addition of PEth blood test in many cases, to create a more complete picture of alcohol consumption.

Let’s dive in.

Understanding EtG in Hair Strand Testing

Ethyl Glucuronide (EtG) is produced in the presence of alcohol, formed in the liver and detectable in various biological samples such as urine, blood, nails, and hair. Its presence is considered a highly specific marker for alcohol consumption in hair. Unlike EtPa, EtG is less likely to be influenced by incidental alcohol exposure such as hair sprays, but it has vulnerabilities of its own. Frequent washing, bleaching, dyeing, and straightening of hair can reduce the concentration of EtG, making it appear as though less alcohol was consumed than in reality.

Understanding EtPa in Hair Strand Testing

Ethyl Palmitate (EtPa) is another marker of ethanol (alcohol) and detectable in hair. However, EtPa in hair strand tests (HST) is susceptible to external contamination from alcohol-based cosmetic products such as hair sprays and serums. This is due to the small amount of alcohol in these products, leading to elevation in the levels of EtPa.

If you look at the back of certain hair styling products, you might see terms like Alcohol Denat, Ethanol, Ethyl Alcohol, and SD Alcohol 40. These are all ingredients containing ethanol that can skew hair strand test results.

Case Study 1: EtPa False Positive Due to Hair Spray

If you tuned into our recent webinar, “Understanding Alcohol Testing in Care Proceedings” (watch on demand here), you may have heard about a gentleman named “Dave” who used to drink but has reduced his drinking volume of late.

In this case, EtG and EtPa were instructed, in conjunction with a PEth test. With regards to the 3 cm cut-off levels, EtG and PEth results were low, recording 30 pg/mg and 210 ng/mL respectively. However, EtPa was well over the cut-off of 350 pg/mg. At first glance, these results may appear conflicting, or even like a positive for EtPa. However, on closer inspection of the collection notes, it was noted that Dave was a heavy “hair styler,” frequently applying ethanol-containing products to his hair, in the form of hair spray.

By reviewing the EtG and PEth results alongside the notes, it seems reasonable to conclude that the EtPa result was, in fact, a false positive.

Case Study 2: Bleaching Cover-Up

Also in the webinar, we discussed a case involving a new mother who was battling to maintain custody of her newborn child. She had been a heavy drinker and, after searching online for “Ways to cheat a hair alcohol test,” she decided to bleach her hair.

EtG was recorded as 9 pg/mg, well under the 30 pg/mg cut-off. However, both EtPa and PEth were over the cut-offs, suggesting heavy alcohol use. Once again, by referring to the notes, there was a comment regarding heavy hair bleaching. Hence, the EtG result in the mother’s hair was disregarded due to potential interference.

Practical Implications for the Legal System

The use of EtG and EtPa in the legal system requires a deep understanding of the science behind these biomarkers and the practical factors that may interfere with test results. Legal professionals and local authorities  involved in alcohol monitoring need to be aware of potential environmental influences, lifestyle factors, and the limitations of these tests to ensure results are interpreted correctly.

For more robust results, AttoLife recommends testing both hair alcohol markers EtG and EtPa alongside a blood alcohol test such as PEth. 

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