Healthcare providers who are concerned that their patients may drink alcohol at harmful levels can perform blood tests to check this. Carbohydrate-deficient transferrin (CDT) is an alcohol biomarker test.It can be used to detect whether someone is an alcoholic or a heavy drinker (four or more drinks per day). It can even be used to determine whether an alcoholic has relapsed.
Traditionally, healthcare providers have used brief alcohol screening tests to determine the patient’s alcohol consumption level. The problem with these screenings is that their accuracy depends on whether the patient honestly tells them how much they drink.
Patients without alcohol problems may accurately self-report their drinking levels. But those who do have problems are more likely to reduce their alcohol intake as much as possible. The bigger the problem, the more likely the patient is to deny heavy drinking.
Therefore, those short screening tests may not produce the most accurate assessment. When health care providers suspect that patients may be alcoholic, the CDT test provides them with another tool.
What is the CDT test?
Transferrin is a substance in the blood that transports iron to the bone marrow, liver, and spleen. When someone drinks too much, it increases certain types of carbohydrate-deficient transferrin. When carbohydrate-deficient transferrin increases, it can be detected in the blood and is therefore a biomarker of alcoholism.
How CDT testing works
People who do not drink alcohol or drink in moderation have lower levels of carbohydrate-deficient transferrin in the blood. Some studies use a cut-off value of less than 1.7%. However, two weeks before the test, at least five days a week, people who drank four or more glasses of alcohol a day had significantly higher CDT levels.
For patients who drink one bottle of wine, five bottles of beer, or half a pint of whiskey a day, the CDT test is very accurate in detecting this level of heavy drinking. Very similar to the A1C test that can detect blood glucose levels within 90 days, the CDT test can detect long-term heavy drinking.
If a person stops drinking, the CDT level will decrease. But if they start drinking again, the level will increase again.
False positives in CDT testing
Not everyone is sensitive to CDT. In a small group of people, heavy drinking will not increase carbohydrate-deficient transferrin levels. Therefore, health care providers who suspect patients of alcohol abuse are encouraged to also use other alcohol biomarker testing.
There are biological factors that can falsely increase CDT levels, such as genetic variants, female hormones, increased body mass index, and end-stage liver disease.Because of these factors, the earliest CDT tests returned false positives, but newer tests can identify genetic variants that can lead to false positives and negatives, as well as patterns caused by alcohol-related liver disease.
Effectiveness of the CDT test
Many studies have been conducted on the effectiveness of using the CDT test to determine whether a patient has alcohol abuse. These studies have found that the test is accurate, but not foolproof.
Confirmation methods include the use of questionnaires, GGT (γ-glutamyl transpeptidase) test, or EtG (ethyl glucuronide) test (to detect alcohol consumption in the past 24 to 72 hours).
Why CDT testing is important
In many medical situations, patients should not drink alcohol, or should not drink large amounts of alcohol. People with diabetes, high blood pressure, hepatitis C or liver disease should not drink a lot of alcohol.
A study found that among the 799 patients under study, 9% of diabetic patients and 15% of hypertensive patients drank harmful levels of alcohol.This could mean that the drinking of millions of people with diabetes and high blood pressure puts their health at risk.
Patients who are taking certain drugs should not drink alcohol because of the risk of reactions to drugs and alcohol. People who are receiving opioid painkillers for pain or who are taking sedatives or sleeping pills should certainly not drink a lot of alcohol because of the risk of central nervous system depression.
If healthcare providers use the CDT test to identify patients with diabetes, high blood pressure, and other alcohol-drinking conditions, medical complications and healthcare costs may be significantly reduced.
Used to monitor recovery
In addition to detecting heavy drinking in alcohol-sensitive patients, the CDT test can also be used in the field of drug abuse to monitor abstinence and relapse.According to the researchers, the CDT test is the only alcohol biomarker test that is sensitive enough to detect a decrease or relapse in alcohol use.
Some psychotherapists and psychiatrists who work with alcoholics use the CDT test to obtain baseline levels during their first contact with the patient. In the next few weeks and months, they can use the CDT test to determine if the person remains awake or if the person has relapsed.