What is PEth testing? Is it a reliable way to check for alcohol markers? What are the pros & cons compared to other types of alcohol test? Read our expert guide to find out…

What is PEth testing?

Phosphatidylethanol (PEth) is the most accurate blood test to determine alcohol abuse. This is because PEth is a direct marker of alcohol, which means that it can only be detected when alcohol has been consumed. Its high specificity (48–89%) and sensitivity of 88–100% is because it is directly related to alcohol consumption.

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.

Sensitivity of PEth blood tests

Biomarkers are used to 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.

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 mean corpuscular volume (MCV), carbohydrate deficient transferrin (CDT) and the liver function test (LFT, which measures various enzymes in the blood that are produced by the liver). While medically useful, these blood tests generally require the daily consumption of over 60 g/day of alcohol over several weeks to cause clinically significant elevations. As such, either normal or chronic and excessive levels of alcohol can be detected. Indirect biomarkers are unable to monitor abstinence or episodes of binge drinking.

PEth is a highly reliable blood test

Because PEth is a direct biomarker of alcohol and requires ethanol for its production, it is a highly reliable blood test for alcohol abuse. 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. The result provides a detection period of up to 3–4 weeks. However, the greater the exposure and/or larger the binge session(s), the longer the period of detection.

In terms of all alcohol tests, PEth is second to the detection of ethyl glucuronide (EtG  – another direct metabolite of ethanol) in hair alcohol testing. However, PEth analysis has the advantage of allowing faster verification as to whether an individual has changed their drinking behaviour.

AlphaBiolabs recommends its Comprehensive Alcohol Analysis Package to support any individual blood test result. This combines hair testing (FAEE [fatty acid ethyl esters] and EtG) with blood tests (CDT, LFT, MCV and PEth) and also includes a Statement of Witness report and sample collection. The Comprehensive Alcohol Analysis Package provides the best insight into an individual’s level of alcohol consumption. Contact AlphaBiolabs to order a PEth alcohol test or other alcohol testing solution including instant breath tests, blood analysis and 3- or 6-month hair analyses to show alcohol consumption over a period of time. Real-time results are also available with SCRAM Continuous Alcohol Monitoring®. For expert advice, please call 0333 600 1300 or email us at