What does a PEth test show?

What does a PEth test show? How is it different to other alcohol tests? Read our latest expert guide to find out…

A PEth test is a blood alcohol test that measures the level of phosphatidylethanol (PEth) in a sample.

PEth is an abnormal phospholipid, which is formed on the surface of red blood cells when alcohol reacts with phosphatidylcholine. Phosphatidylcholine is also a phospholipid and a major constituent of cell membranes.

Because ethanol is needed for the production of PEth, it is a direct biomarker of alcohol. In other words, 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. High levels of alcohol consumption produce high concentrations of PEth. Low alcohol consumption leads to low PEth concentrations.

The PEth levels that can be measured in a blood alcohol test can range from 10 µg/L to over 210 µg/L.

• PEth level < 10 µg/L would denote abstinence or very low alcohol consumption in the past month.
• PEth level 10–35 µg/L would denote low or occasional alcohol consumption in the past month.
• PEth level 35–210 µg/L would denote social or moderate alcohol consumption in the past month.
• PEth level > 210 µg/L would denote excessive alcohol consumption in the past month.

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. It is also the only blood alcohol test that can be performed on pregnant women.

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