Phosphatidylethanol (PEth) and ethyl glucuronide (EtG) are both direct and specific biomarkers of alcohol.
This means they are only created when ethanol is metabolized or reacts with substances in the body. In other words, they can only be detected when alcohol has been consumed.
PEth alcohol testing
Phosphatidylethanol (PEth) is the most accurate of blood tests to determine alcohol abuse. Its high specificity (48–89%) and sensitivity of 88–100% is because it is directly related to alcohol consumption.
In terms of all alcohol tests, PEth is second to the detection of EtG in hair alcohol testing (see below). However, PEth analysis has the advantage of allowing faster verification as to whether an individual has changed their drinking behaviour.
PEth is actually an abnormal phospholipid, which is produced after alcohol exposure in red blood cell membranes. It requires ethanol for its production and is formed on the surface of a red blood cell when the alcohol reacts with phosphatidylcholine. PEth production begins as soon as ethanol is consumed and accumulates in blood with frequent alcohol consumption.
Drinking experiments show that PEth can be detected in blood after 1–2 hours and for up to 12 days after a single drinking episode. In addition, daily alcohol consumption of more than 60 g ethanol can clearly be distinguished from lower alcohol consumption. As such, PEth testing can detect chronic and single-drinking episodes. It can also be used to monitor abstinence, drinking behaviour and identify relapse. PEth analysis can also verify whether an individual has changed their pattern of alcohol consumption.
The table below shows the range of PEth levels that can be measured.
| PEth level (ng/mL ) | |
| < 20 | Abstinence or low alcohol consumption in the past month prior to sample collection. |
| 20–210 | Social/ moderate alcohol consumption in the past month prior to sample collection. |
| > 210 | Excessive alcohol consumption in the past month prior to sample collection. |
Window of detection: up to 3–4 weeks.
Advantages: PEth testing can monitor abstinence, drinking behaviour and identify relapse. It can also verify whether individuals have changed their patterns of alcohol consumption.
Hair EtG testing
EtG testing is the most reliable hair test when determining the levels of alcohol consumed. Detection of the biomarker can show a change in pattern of alcohol consumption. When an individual stops drinking, the levels of EtG in hair decrease in a linear pattern over 3–6 months.
However, EtG may be lost through the use of hair dye and excessive hair washing. For this reason, alcohol abuse can be determined in head hair by detecting two metabolites of alcohol: EtG and the second metabolite is a fatty acid ethyl ester (FAEE); ethyl palmitate (EtPa).
These markers of alcohol intake are incorporated into the hair via different routes: EtG via sweat and EtPa via sebum (an oily substance secreted by glands in the
scalp). The reasons that both EtG and EtPa markers are analyzed is because they are affected by external factors in different ways. Therefore, performing these two different types of hair analyzes can assist in building evidence to support.
If head hair is not available for testing, body hair can be used, but this only measures EtG.
The time period would also be more approximate due to the nature of body hair growth. Chest, arm, leg and beard hair can be analyzed to provide up to a 12-month overview. In the case of body hair testing, we would also recommend a blood test to detect alcohol biomarkers, in conjunction with clinical assessment, to gain a greater insight into an individual’s alcohol use.
Window of detection: 3- or 6-month overview. (Body hair: up to 12-month overview of EtG only).
Advantages: Alcohol consumption can be retrospectively estimated over a period of months.
Nail EtG testing
EtG biomarkers can become trapped within the keratin fibres along the length of a nail providing a detection period of up to 12 months.
Approximately 10 mg of nail is required for the test. The nail is collected as close to the nail bed as possible. If the nail is long (5 mm or above) then only one would be required. If the nails are short then it may be best to take clippings from several nails. Toe nails as well as finger nails can be used, but not a mixture of both. The advantages of using toe nails is that there is less potential for environmental exposure.
Acrylic nails, Shellac and other forms of nail varnish would need to be removed as this may damage the surface of the nail and impact on the results.
Because only EtG can be detected, we would also recommend a blood test to detect alcohol biomarkers, in conjunction with clinical assessment, to gain a greater insight into an individual’s alcohol use.
Window of detection: up to a 12-month overview
Advantages: simple-to-collect sample to measure levels of EtG. Ideal for those cases where hair testing is not possible (such as the donor has no or little hair, for religious reasons, and for those concerned with their appearance).
In summary
| Purpose | PEth | EtG in hair | EtG in nails |
| Abstinence | ✔ | ✖ | ✔ |
| Social drinker | ✔ | ✖ | ✖ |
| Chronic and excessive drinker | ✔ | ✔ | ✖ |
| Recent use (hours) | ✖ | ✖ | ✖ |
| Recent use (days) | ✔ | ✖ | ✖ |
| Window of detection (up to) | 3–4 weeks | 12-month* | 12-month* |
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Last reviewed: 05/26/2023
Marie Law
Head of Toxicology at AlphaBiolabs
A highly-skilled and respected scientist with over 13 years’ experience in the field of forensics, Marie joined AlphaBiolabs in 2022 and oversees the company’s growing toxicology team.
As Head of Toxicology, Marie’s day-to-day responsibilities include maintaining the highest quality testing standards for toxicology and further enhancing AlphaBiolabs’ drug and alcohol testing services for members of the public and the legal sector.
