What is PEth? An introduction to PEth testing

PEth testing

PEth is a highly specific and sensitive modern alcohol testing method for proof of consumption within the previous 4 weeks.

Previously a trained phlebotomist was required to collect enough blood for a CDT and several LFT tests. Interpretation of results was difficult because each test on its own could be affected by factors other than alcohol consumption (eg cirrhosis, obesity, diabetes, medication, age).

Phosphatidylethanol16:0/18:1 (PEth) is a group of phospholipids formed exclusively in the body when alcohol is consumed.  A dried blood spot (DBS) specimen taken from a finger prick is all we need to measure PEth. We use a highly sensitive and selective liquid chromatography – tandem mass spectrometry (LC-MS/MS) technique.  The analytical method has been awarded ISO/IEC 17025 accreditation.


Highly Specific:

PEth is only formed in the body when alcohol is consumed. Phosphatidylethanols are a group of phospholipids formed exclusively in the presence of ethanol. PEth 16:0/18:1 is measured as a specific alcohol biomarker.

Unlike CDT and LFT markers, PEth is not influenced by any liver disease which makes it useful in monitoring heavy drinkers with hepatic pathology.

Highly Sensitive:

PEth is more sensitive than the indirect alcohol marker CDT (carbohydrate-deficient transferrin).  PEth levels rise even after a single drinking episode. While PEth forms at low doses of alcoholic beverages, it has been found to be insensitive to incidental ethanol exposures, such as mouthwash and antibacterial hand sanitisers.  To protect against false positives, however, PEth is currently considered to be an indicator of purposeful alcohol ingestion at values > 20 ng/ml.

Normalisation Time:

This describes the time it takes for a biomarker in blood to halve its concentration.  Too quick and donor must only abstain from alcohol for a few days before testing for the biomarkers to drop to normal levels.  Too slow and the biomarker levels don’t drop even after a significant period of abstinence. Elevated PEth levels indicate alcohol consumption up to 4 weeks prior to specimen provision.

If a longer window of investigation is required (3 – 6 months), testing ethyl glucuronide in hair perfectly complements PEth testing.


A dried blood spot (DBS) from a finger prick provides a stable specimen for analysis without the need for a phlebotomist.

Measured PEth values are evaluated against the following 3 tiers for the purpose of interpretation:

  • <20 ng/ml – Light or No Consumption – Supports claim of abstinence or low alcohol consumption up to a month prior to specimen collection. Low alcohol consumption is considered as < 1-2 standard alcoholic drinks per day for several days a week.
  • 20-200 ng/ml – Significant Consumption – Indicates moderate level of alcohol consumption up to a month prior to specimen collection. Significant alcohol consumption is considered as 2-4 standard alcoholic drinks per day for several days a week.
  • >200 ng/ml – Heavy Consumption – Indicates Excessive alcohol consumption up to a month prior to the specimen collection. Heavy alcohol consumption is considered as more than 4 standard alcoholic drinks per day for several days a week.

Note: The frequency of alcohol consumption can affect PEth results; ten drinks consumed in one episode will produce a higher PEth level than if ten drinks were consumed in five episodes.

Abstinence from alcohol means no intake of any alcoholic beverages or other alcohol containing products over a pre-defined time period.

The World Health Organisation[1] defines chronic excessive alcohol consumption corresponds to an average of 60g or more of pure ethanol per day over several months (60g ethanol equates to approximately 7 ½ units of alcohol).

The UK Chief Medical Officers advise both men and women not to drink more than 14 units of alcohol per week on a regular basis.[2]

RTS now routinely offer PEth alcohol testing for abstinence for both workplace and medico-legal customers offering further support against substance misuse.

For further information contact us today.

E-mail: www.testingservices@randox.com

Telephone: +44 (0) 28 9445 1011


[1] International guide for monitoring alcohol consumption and related harm.  World Health Organisation, Dept. of Mental Health and Substance Abuse, Geneva, 2000 pp 51-54

[2] Drinkaware.co.uk