Understanding blood and hair alcohol testing
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. These biomarkers can 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.
AlphaBiolabs undertakes four blood alcohol tests to measure biomarkers. These are:
- Phosphatidylethanol (PEth)
- Liver function test (LFT)
- Carbohydrate deficient transferrin (CDT)
- Mean corpuscular volume (MCV).
Their window of detection is around 4 weeks.
PEth is the most accurate of the four blood tests to determine alcohol abuse because it is a direct biomarker of alcohol. 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 LFT, MCV and CDT. While medically useful, these blood tests generally require the daily consumption of over 60 g/day of alcohol.
With all the blood tests, we would also recommend a hair strand test (if possible) to detect alcohol biomarkers, in conjunction with clinical assessment, to gain a greater insight into an individual’s alcohol use.
PEth alcohol testing
PEth is the most accurate of the four blood tests to determine alcohol abuse. This is because PEth is a direct biomarker 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.
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 (see below). However, PEth analysis has the advantage of allowing faster verification as to whether an individual has changed their drinking behaviour.
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.
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.
Liver function test (LFT)
Alcohol can be toxic to the liver. A person who consumes excessive amounts of alcohol will damage their liver and may experience decreased liver function. A LFT measures five enzymes in the blood that are produced by the liver. An abnormal result indicates a problem with the liver. For example, an elevated aspartate aminotransferase (AST) value is a biochemical indicator of possible alcohol abuse.
The panel of markers tested include total bilirubin, AST, alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma glutamyl transferase (GGT) to ensure the result is as accurate as possible.
Carbohydrate deficient transferrin (CDT)
In cases where a sample donor is excessively using alcohol, an elevated CDT reading is usually seen.
Transferrin is a protein largely made in the liver that regulates an individual’s iron absorption into the blood. It attaches iron molecules and transports them to the bone marrow, spleen and liver. An individual who drinks too much alcohol increases certain types of transferrin that are carbohydrate-deficient. When CDT increases, it can be measured in the bloodstream and is therefore a biomarker of alcohol abuse.
People who do not drink, or drink moderately, will have lower CDT levels in their blood. But people who drink four or more drinks a day, at least five days a week for 2 weeks prior to the test will have CDT at significantly greater levels. The CDT test can thus detect heavy alcohol consumption over a long period of time and is a measure of chronic alcohol consumption. If a person stops drinking, the CDT levels will return to normal levels within 4 weeks. If they start drinking again, the levels will once again rise.
Mean corpuscular volume (MCV)
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 develop abnormally and become large. As a result, the MCV index becomes higher than normal.
Elevated MCV is common in alcoholics. The changes in red blood cell development persists as long as drinking continues. MCV takes several weeks of heavy drinking to become elevated. However, alcohol-induced bone marrow damage is reversible. Although, it may take several months before MCV returns to a normal level after abstinence.
Some unrelated conditions can result in higher MCV levels. The test is less specific for alcohol abuse in patients with conditions that can influence the size of red blood cells, such as vitamin deficiencies, liver disease, underactive thyroid disease and smoking.
As a stand-alone alcohol abuse indicator MCV has somewhat low sensitivity. However, when combined with other blood tests it can support a diagnosis of excessive drinking.
Hair alcohol testing
Biomarker testing in head hair can establish a person’s history of alcohol consumption for up to 6 months. The recommended minimum length of hair is a 3 cm section taken from nearest the scalp which covers a 3-month time period. This is consistent with the consensus on hair alcohol testing for chronic excessive alcohol consumption published by the Society of Hair Testing (SoHT) in June 2009 .
AlphaBiolabs determines alcohol abuse in head hair by detecting two metabolites of alcohol: ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEEs). These markers of alcohol intake are incorporated into the hair via different routes: EtG via sweat and FAEEs via sebum (an oily substance secreted by glands in the scalp). The reasons that both EtG and FAEE markers are analysed is because they are affected by external factors in different ways. Therefore, performing these two different types of hair analyses can assist in building evidence to support the diagnosis of chronic excessive alcohol consumption with a greater degree of certainty.
Head hair is preferred over body hair for alcohol testing. However, body hair can be useful to measure EtG if head hair is not available. The time period would also be more approximate due to the nature of body hair growth. Chest, arm, leg and beard hair can be analysed to provide up to a 12-month overview. With body hair, we would also recommend a blood test to detect alcohol biomarkers, in conjunction with clinical assessment, to gain a greater insight into an individual’s alcohol use.