PEth vs. Other Tests

Liz Wood Alphabiolabs

By Liz Wood, Health Testing Specialist at at AlphaBiolabs
Last reviewed: 22/01/2024

AlphaBiolabs offers a full alcohol testing service ranging from breath tests, blood analysis and hair analyses to show alcohol consumption over a period of time.

Continuous results are also available using an innovative alcohol monitoring bracelet, SCRAM CAM®.

Blood alcohol tests

Blood alcohol tests are used to measure the level of alcohol in an individual’s blood. When alcohol is consumed, it is absorbed into the bloodstream and about 90% of it is broken down in the liver. The rest is passed out of the body in urine and exhaled breath. On average it takes the liver about 1 hour to break down 1 unit of alcohol.

If a person is drinking excessively, and over an extended period of time, the effects on the liver and other cells in the body can be measured by analysing biomarkers in the blood. These biomarkers can detect the consumption of alcohol or its harmful effects on the body.

Direct biomarkers are created when ethanol is metabolised or reacts with substances in the body. Indirect biomarkers are enzymes or cells, which undergo measurable changes in response to acute or chronic alcohol consumption. AlphaBiolabs undertakes four blood alcohol tests to measure biomarkers. These are phosphatidylethanol (PEth), liver function test (LFT), carbohydrate deficient transferrin (CDT) and mean corpuscular volume (MCV).

PEth alcohol testing

Phosphatidylethanol (PEth) is the most accurate of the four blood tests to determine alcohol abuse. This is because PEth is a direct biomarker of alcohol, which means that it can only be detected when alcohol has been consumed. Its high specificity and sensitivity is because it is directly related to alcohol consumption.

In comparison to other alcohol tests, PEth is second only to the detection of ethyl glucuronide (EtG – another direct metabolite of ethanol) 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.

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. PEth production begins as soon as ethanol is consumed and accumulates in blood with frequent alcohol consumption.

Window of detection: up to 3–4 weeks. However, the greater the exposure and/or larger the binge session(s), the longer the period of detection.

Advantages: PEth testing can monitor abstinence, drinking behaviour and identify relapse. It can also verify whether individuals have changed their patterns of alcohol consumption.

  • Monitor abstinence, drinking behaviour and identify relapse
  • Verify whether individuals have changed their patterns of alcohol consumption
  • AlphaBiolabs’ Finger prick PEth Alcohol Test simply requires a few blood drops, collected using a finger prick device
  • No specialist phlebotomy or venepuncture skills required to perform the collection, making the process much simpler and more cost-efficient for customers
  • Virtually pain-free method of blood sample collection is also ideal for Sample Donors who are needle phobic or have poor vein access
  • PEth is also the only form of blood alcohol testing that is recommended to be performed during pregnancy or within two months of birth

Other blood tests

Indirect biomarkers of alcohol become elevated when enough alcohol has been consumed over a sufficiently large time period to damage the body. Indirect biomarker tests include the liver function test (LFT), mean corpuscular volume (MCV) test and carbohydrate deficient transferrin (CDT) test. While medically useful, these blood tests generally require the daily consumption of over 60 g/day of alcohol.

With all the blood tests, we would also recommend a hair strand test (if possible) to detect alcohol biomarkers, in conjunction with clinical assessment, to gain a greater insight into an individual’s alcohol use.

Liver function test (LFT)

Alcohol can be toxic to the liver. A person who consumes excessive amounts of alcohol will damage their liver and may experience decreased liver function. A LFT measures three enzymes in the blood that are produced by the liver. An abnormal result indicates a problem with the liver. For example, an elevated aspartate aminotransferase (AST) value is a biochemical indicator of possible alcohol abuse.

The panel of markers tested include AST, alanine aminotransferase (ALT) and gamma glutamyl transferase (GGT) to ensure the result is as accurate as possible.

Carbohydrate deficient transferrin (CDT)

In cases where a sample donor is excessively using alcohol, an elevated CDT reading is usually seen.

Transferrin is a protein largely made in the liver that regulates an individual’s iron absorption into the blood. It attaches iron molecules and transports them to the bone marrow, spleen and liver. An individual who drinks too much alcohol increases certain types of transferrin that are carbohydrate-deficient. When CDT increases, it can be measured in the bloodstream and is therefore a biomarker of alcohol abuse.

People who do not drink, or drink moderately, will have lower CDT levels in their blood. But people who drink four or more drinks a day, at least five days a week for 2 weeks prior to the test will have CDT at significantly greater levels. The CDT test can thus detect heavy alcohol consumption over a long period of time and is a measure of chronic alcohol consumption. If a person stops drinking, the CDT levels will return to normal levels within 4 weeks. If they start drinking again, the levels will once again rise.

Mean corpuscular volume (MCV)

MCV refers to the size of red blood cells. Red blood cells carry oxygen in blood to all parts of the body. Heavy drinking over longer periods damages the bone marrow where the red blood cells are produced. The effect is that the red blood cells develop abnormally and become large. As a result, the MCV index becomes higher than normal.

Elevated MCV is common in alcoholics. The changes in red blood cell development persists as long as drinking continues. MCV takes several weeks of heavy drinking to become elevated. However, alcohol-induced bone marrow damage is reversible. Although, it may take several months before MCV returns to a normal level after abstinence.

Some unrelated conditions can result in higher MCV levels. The test is less specific for alcohol abuse in patients with conditions that can influence the size of red blood cells, such as vitamin deficiencies, liver disease, underactive thyroid disease and smoking.

As a stand-alone alcohol abuse indicator MCV has somewhat low sensitivity. However, when combined with other blood tests it can support a diagnosis of excessive drinking.

Window of detection: Around 4 weeks.

Advantages: useful for detecting chronic and excessive alcohol consumption.

Hair alcohol testing

Biomarker testing in head hair can establish a person’s history of alcohol consumption for up to 6 months. The recommended minimum length of hair is a 3 cm section taken from nearest the scalp which covers a 3-month time period. This is consistent with the consensus on hair alcohol testing for chronic excessive alcohol consumption published by the Society of Hair Testing (SoHT) in June 2019 [1].

AlphaBiolabs determines alcohol abuse in head hair by detecting two metabolites of alcohol: ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEEs). These markers of alcohol intake are incorporated into the hair via different routes: EtG via sweat and FAEEs via sebum (an oily substance secreted by glands in the scalp).

The reasons that both EtG and FAEE markers are analysed is because they are affected by external factors in different ways. Therefore, performing these two different types of hair analyses can assist in building evidence to support the diagnosis of chronic excessive alcohol consumption with a greater degree of certainty.

Head hair is preferred over body hair for alcohol testing. However, body hair can be useful to measure EtG if head hair is not available. The time period would also be more approximate due to the nature of body hair growth. Chest, arm, leg and beard hair can be analysed to provide up to a 12-month overview. In all cases, 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: useful for detecting long-term alcohol use. History of alcohol use can be established. Chronic and excessive levels can be measured.

Comprehensive alcohol analysis package

AlphaBiolabs recommends its Comprehensive Alcohol Analysis Package to provide the best insight into an individual’s level of alcohol consumption.

This combines hair testing (FAEE and EtG) with blood tests (PEth, CDT, LFT and MCV) and also includes an Expert Report and sample collection.

Nail alcohol testing

Our nail alcohol testing analyses samples for ethyl glucuronide (EtG). These EtG biomarkers become trapped within the keratin fibres along the length of the 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).

SCRAM Continuous Alcohol Monitoring®

SCRAM Continuous Alcohol Monitoring® (SCRAM CAM®) provides an accurate way of pinpointing exactly how much alcohol has been ingested and when. This device is a bracelet that is worn on the ankle and tests for the presence of alcohol in perspiration. It is the first device of its kind to detect the drinking of alcohol in real-time and the results are automatically gathered and uploaded to a base station.

The wireless base station could be located in the individual’s home, a solicitor’s office or anywhere convenient. Incidents of drinking and tampering are recorded and made known weekly, monthly or at the end of the testing programme.

The principle behind this transdermal form of testing is based on how the human body metabolises alcohol. Once alcohol is absorbed and distributed through the bloodstream, it is eliminated in various forms. About 1–2% of the alcohol that is consumed is eliminated through the skin in the form of perspiration. These transdermal emissions are sampled every 30 minutes. As such, the frequency and pattern of alcohol consumption can be easily shown.

This method of testing for alcohol makes it easier to adhere to low or no-alcohol schemes as samples are taken on a continuous basis, every half-an-hour, 24 hours a day, 7 days a week. The technology is so advanced it can even differentiate between very low alcohol consumption (such as 1–2 units) and environmental alcohol sources. This helps enforce participant sobriety, compliance and accountability. This form of continuous monitoring (also called sobriety tagging) can provide local authorities, courts and child-protection agencies with the tools to change behaviours in vulnerable and higher-risk alcohol-dependent clients.

Window of detection: 1 day up to as many months as needed.

Advantages: ankle bracelet detects around-the-clock alcohol in real time. Can pinpoint alcohol use at the exact time of day and on which day.

Breath alcohol testing

Breath test devices (breathalysers) are used to measure the alcohol concentration in a person’s breath. As such, they measure current alcohol consumption. They do not measure historical use of alcohol. This means that this method of testing can be used to prove sobriety as and when needed. The person being tested for alcohol use blows into the breath alcohol device.

They are advised not to take anything by mouth in the 20 minutes prior to breath sampling. The results are given as a digital readout, known as the breath alcohol concentration (BAC), which shows the level of alcohol in the breath at the time the test was taken. A second reading is only taken if the first reading is greater than zero.

The devices allow automatic sampling and calibration and all use electrochemical fuel cell technology. When alcohol comes in contact with the sensor, it generates a small amount of electricity. The electricity is measured and converted into the breathalyser reading. The amplitude of the electric current is dependent on the amount of ethanol detected in the breath sample.

UK-certified breathalysers assume that the subject being tested has a 2300-to-1 partition ratio in converting alcohol measured in the breath to estimates of alcohol in the blood. This measure is in direct proportion to the grams of alcohol to every 1 ml of blood. AlphaBiolabs can provide a number of Home Office-type approved breathalysers dependent on your individual needs.

Window of detection: measures current alcohol consumption so can test for sobriety as and when needed.

Advantages: compact breath alcohol test devices are used by UK police for roadside drink-driving checks, and by social workers for point-of-care testing when evaluating child protection issues.

If you have further questions about PEth vs. other tests

For expert advice on legal alcohol testing solutions, please call our Customer Services team on 0333 600 1300 or email us at

Download the Info Sheet
Download this page as a printable PDF

Liz Wood, AlphaBiolabs

Liz Wood

Health Testing Specialist at AlphaBiolabs

Liz joined AlphaBiolabs in 2021, where she holds the role of Health Testing Specialist.

As well as overseeing a range of health tests, she is also the lead on several validation projects for the company’s latest health test offerings.

During her time at AlphaBiolabs, Liz has played an active role in the validation of the company’s Genetic Lactose Intolerance Test and Genetic Coeliac Disease Test.

An advocate for preventative healthcare, Liz’s main scientific interests centre around human disease and reproductive health. Her qualifications include a BSc in Biology and an MSc in Biology of Health and Disease.

Related articles…

PEth vs. EtG Testing

AlphaBiolabs undertakes blood testing to measure PEth, and hair testing and nail clipping analysis to measure EtG.

Blood alcohol testing methods

In this article, we look at the different types of blood alcohol test, what each test looks for, and how these tests can be used alongside other methods.

How do you prove abstinence from alcohol?

In this article, we look at alcohol abstinence – what it is, how you can prove alcohol abstinence, who might need to prove that they are abstinent from alcohol, and where you can buy an alcohol test.