Blood testing has been used to highlight potential alcohol abuse for decades and is therefore an established and relied upon method. There are a number of important considerations when selecting blood testing and different routes you can choose.
The first step is to understand the difference between a direct and indirect biomarker. The majority of blood testing conducted is based on indirect biomarkers, this means the test is looking at how the body and/or its organs are functioning. If they are within normal ranges or if they are outside the normal range. The indirect biomarkers used are often highly influenced by someone who has been drinking, however they may also be outside the normal range for other reasons.
Direct biomarkers on the other hand are produced only when someone has consumed alcohol or increased their blood alcohol levels. This ensures you have an accurate picture of alcohol consumption that is not affected by other factors.
Indirect alcohol abuse testing options:
- Carbohydrate-deficient Transferrin (CDT)
- Liver Function Test (LFT)
- Full Blood Count (Mean Conspicuous Volume - MCV)
Direct alcohol abuse testing options:
- Phosphatidyl Ethanol (PEth)
Carbohydrate-deficient Transferrin (CDT)
A CDT test is one of the most accurate indirect biomarkers with a sensitivity of 77% at detecting chronic alcohol abuse. The test works by establishing the percentage of transferrin that is carbohydrate-deficient. In normal conditions individuals will fall into the range of 0-1.6%. In some cases, the range can go as high as 10% and this can be an indicator of extreme alcohol abuse. However, there are numerous reasons for the CDT to be outside of the normal range, including medication, health, previous alcohol consumption, or if the individual has liver disease.
Transferrin is produced in the liver with the purpose to ‘transfer’ iron molecules from the intestine into organs and cells that need iron to function. It is therefore present in everyone under normal circumstances.
Normal transferrin has carbohydrates attached to it, yet when someone consumes alcohol at the rate of 5 units per day, the liver is unable to produce the transferrin in the same way. As a result, the amount of carbohydrates attached to the transferrin are reduced leading it to be deficient in carbohydrates.
Liver Function Testing (LFT)
The main biomarker within the Liver Function Test that is observed is the Gamma glutamyl transferase (GGT). Studies how shown that GGT is a potential indicator of an individual's alcohol use.
The normal range of GGT within the DNA Legal laboratory is 10-71 iU/L for men. If an individual’s test results are outside of this range, it can be an indicator of alcohol abuse.
LFT is the second most reliable indirect marker, however, there have been numerous cases where heavy alcohol users have normal LFT readings. Medication such as warfarin, drugs used for epilepsy, antidepressants, barbiturates and cimetidine can increase levels of GGT. An isolated rise in GGT is most commonly due to alcohol abuse, or enzyme-inducing drugs.
LFTs do not always produce reliable results. The results may be normal in patients who suffer from serious liver disease and abnormal in patients without liver diseases or other diseases that may interfere with results.
Mean Corpuscular Volume (MCV)
The MSV test is part of a full blood count (FBC) and is used to identify recently ingested alcohol. The test works by looking at the average volume of red blood cells in a specimen. MCV is elevated or decreased in accordance with the average cell size.
The normal range of MCV within the DNA Legal laboratory is 80-99 fL.
Whilst this test can provide some possible indication of alcohol abuse, it is the least accurate of all blood testing with a sensitivity rate of only 44%. This is due to multiple factors, including the number of reasons why an individual may have MCV readings outside of the normal range, such as vitamin deficiencies, medication, and previous alcohol consumption. In addition to this, studies have shown that heavy alcohol consumers can have normal MCV readings and those who have not consumed alcohol can have abnormal readings. Results from this form of testing should be used with caution.
Phosphatidylethanol (PEth) Testing
PEth is a direct biomarker meaning it is only produced when an individual has consumed alcohol. This means that it has a sensitivity rate of over 99%, far exceeding other blood testing techniques.
This test is designed to show if an individual has consumed an excessive amount of alcohol within the past 30 days (3-4 weeks). Due to the fact that PEth is a direct biomarker, it is not affected by age, gender, health, or previous alcohol abuse issues. If levels of PEth are detected in the blood stream it is because the individual has consumed alcohol. In order to generate enough detectable PEth the individual must drink in a way that raises their blood alcohol concentration level.
PEth is fast becoming the testing choice over indirect biomarkers such as CDT, LFT and MCV when determining an individual’s alcohol consumption.
The DNA Legal blood testing laboratory has proposed that PEth levels greater than 210.48 µg/l indicates excessive alcohol abuse or binge drinking within the last 30 days. If the individuals’ reading falls above 35 µg/l this suggests that some level of alcohol consumption has occurred. When the individual’s PEth levels are between 35 µg/l and 210 µg/l it indicates social drinking.
DNA Legal and blood alcohol testing
Traditional blood testing methods have relied on indirect markers that offer an indication of alcohol consumption but have many limitations and are only 77% sensitive, and some are as low as 44%. DNA Legal provide direct biomarker testing such as PEth, a highly accurate option with 99% sensitivity. As with all alcohol testing, it is advised blood testing is used in combination with other methods such as hair testing and fingernail testing.