Finger prick PEth Alcohol Testing

Drinking experiments show that Phosphatidylethanol (PEth) can be detected in blood after 1-2 hours and for up to 12 days after a single drinking episode.

Additionally, daily alcohol consumption of more than 60g of ethanol can be clearly distinguished from lower alcohol consumption.

This means that PEth testing can detect chronic and single-drinking episodes. It can also be used to monitor abstinence, drinking behaviour, identify relapse, and verify whether an individual has changed their pattern of alcohol consumption.

The table below shows the range of PEth levels that can be measured using an AlphaBiolabs’ blood alcohol PEth test.

There are four main types of blood alcohol testing that legal professionals can call upon for supporting evidence in a case – all of which can provide a four-week historic overview of alcohol use:

• Phosphatidylethanol (PEth) test
• Carbohydrate Deficient Transferrin (CDT) test
• Liver Function Test (LFT)
• Mean Corpuscular Volume (MCV) test

Unlike CDT, LFT and MCV – all of which are indirect biomarkers of alcohol, whose presence can be affected by pre-existing medical conditions and medications, among other factors – PEth is a direct biomarker of alcohol.

As an abnormal phospholipid, it requires ethanol for its production, meaning that it is only present in the body when alcohol has been consumed.

PEth production begins as soon as ethanol is consumed and accumulates in the blood with frequent alcohol consumption, giving it a high specificity and sensitivity.

Drinking experiments show that PEth can be detected in blood after one to two hours, and for up to 12 days after a single drinking episode.

In addition, daily alcohol consumption of more than 60g of ethanol (7.5 units) can clearly be distinguished from lower alcohol consumption, meaning that PEth testing can be used to detect chronic and single-drinking episodes.

The wealth of information provided by a PEth test, alongside its conclusiveness, is what makes it the most essential of all blood alcohol tests, enabling us to monitor abstinence, drinking behaviour, or identify relapse.

PEth analysis is also the only blood alcohol test that is recommended to be undertaken during pregnancy or within two months of the birth.

The PEth result provides a detection period of up to 4 weeks (an approximate month) prior to collection. However, the greater the exposure and/or larger the binge session(s), the longer the period of detection.

PEth is second only to the detection of ethyl glucuronide (EtG) and ethyl palmitate (EtPa), a fatty acid ethyl ester (FAEE), in the hair.

Both EtG and EtPa are biomarkers of alcohol and give us a highly accurate insight into patterns of drinking, with a three- or six-month overview of usage. The PEth result provides a detection period of up to 4 weeks (an approximate month) prior to collection.

Each is absorbed into the hair via different routes, and their levels can assist in assessing excessive alcohol consumption.

EtG is water soluble, produced in the liver and can be impacted by various hair treatments including excessive washing.

EtPa is formed in the sebaceous glands from ethanol diffusing from the blood circulation and then deposited into hair primarily from sebum (from the oil glands on the scalp). EtPa (FAEE) is lipophilic so while not water soluble, its presence can be affected using alcohol-containing hair products such as sprays, gels, and wax.

Because of their respective strengths and weaknesses, both EtG and EtPa tests should be performed together, and their findings used to support each other, as shown in LB Richmond v B & W & B & CB [2010] EWHC (2903) Fam, where Mr Justice Moylan gave guidance on the evidential worth of hair strand testing.

Within this guidance, it was also stressed that hair strand tests/hair alcohol tests should not be used in isolation to reach evidential conclusions.

By performing these tests in conjunction with PEth and other blood tests, a more holistic conclusion can be drawn as to a person’s alcohol use.