There are 2 types of alcohol biomarker: 1) direct biomarkers 2) indirect biomarkers Although widely considered the gold-standard in alcohol testing, direct biomarkers are created when ethanol is metabolised or reacts with substances in the body, so they are only useful for a short period of time after alcohol consumption. Indirect biomarkers are enzymes or cells that change in response to acute or chronic alcohol consumption so they can provide information for days, weeks and even months after ethanol is metabolised. Unfortunately, most indirect biomarkers - including those derived from Full Blood Count (FBC) and Liver Function Tests (LFT) - have a low sensitivity and specificity, which limits their utility. In recent years, however, evidence has emerged that Phosphatidylethanol (PEth) is directly correlated with alcohol consumption and has high sensitivity and specificity as a biomarker. 2 PEth also has the advantage of detecting alcohol consumption for 30 days before the test and distinguishing between heavy, moderate and occasional alcohol use — without health, gender, age or previous alcohol issues affecting on the results.

How is PEth extracted?

There are two common PEth extraction methods: venepuncture and finger-prick testing. Venepuncture involves drawing blood from a vein, typically in the arm or hand. The blood is then stored and transported to a lab, where PEth is analysed. Finger-prick testing is similar to the test for blood sugar in diabetes. The finger tip is “pricked” so that a few drops of capillary blood drips onto a thin sheet of paper. The blood then dries and is sent to a laboratory for analysis. This is called Dry Blood Spot (DBS) analysis.

Venepuncture vs finger-prick testing: which is the best PEth extraction method?

Sample stability

Since analysis is not performed immediately after sample collection, it is essential that PEth remains as close to its original concentration as possible. So how does PEth stability differ between the two extraction methods?

How stable is PEth is venepuncture/whole blood samples?

At most temperatures, the PEth concentration degrades quickly and significantly in whole blood samples collected by venepuncture. This can be prevented by storing samples at -80 degrees celsius, but even then, it must be analysed within 30 days.

How stable is PEth in finger-prick/dry blood spot samples?

Once blood spots collected by finger-prick testing have dried, they remain stable at room temperature for 30 days. Stored at -80 degrees celsius, PEth remains stable in Dry Blood Spot Cards for months.


How invasive is venepuncture?

Venepuncture is one of the most invasive procedures in health care. Adverse effects include pain and/or bruising at the site of puncture, fainting, nerve damage and haematoma.

How invasive is finger-prick testing?

Finger-prick testing is still an invasive procedure but it’s much less invasive - with fewer adverse effects - than venepuncture.

Verdict: the best PEth extraction method Is...

In comparison to venepuncture, finger-prick testing is a less invasive, more convenient and more accurate way to extract PEth for the analysis of recent alcohol consumption.

Guaranteed 3-day PEth analysis

Most UK laboratories only offer PEth analysis from whole blood (venepuncture) samples. Of those that provide DBS analysis, most don’t have in-house PEth testing facilities. This means having to wait for your samples to be shipped to and from overseas labs. Cansford Labs is the only UK company to provide in-house PEth analysis- and the only one to guarantee 3-day analysis of PEth samples. Request a free PEth test quote now.