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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.

What biomarkers are measured?

AlphaBiolabs undertakes four blood alcohol tests, which measure biomarkers, these are:

  • Liver function test (LFT)
  • Carbohydrate deficient transferrin (CDT)
  • Mean corpuscular volume (MCV)
  • Phosphatidylethanol (PEth)

A person who consumes excessive amounts of alcohol will damage their liver and may experience decreased liver function. A liver function test (LFT) measures the effects of alcohol on various liver enzymes in the blood. Abnormal results can indicate a problem with the liver.

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

Mean corpuscular volume (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 do not develop properly and become abnormally large. As a result, the MCV index becomes higher than normal, which persists as long as drinking continues.

Phosphatidylethanol (PEth) is formed on the surface of red blood cells when alcohol reacts with phosphatidylcholine. This means that it is a direct biomarker of alcohol that 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.

Accuracy of PEth blood tests

Because PEth requires ethanol for its production and is thus a direct biomarker of alcohol, it is a highly reliable blood test for alcohol abuse. Drinking experiments with PEth demonstrate that 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. Contact AlphaBiolabs to find out more about PEth alcohol testing or to order other alcohol testing solutions including instant breath tests, other blood tests 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 Customer Services on 0333 600 1300 or email us at