Carbohydrate-deficient transferrin (S-CDT) is used for recognising high alcohol consumption. Excessive use of alcohol is a risk factor for many diseases.
The liver cells produce a protein known as transferrin, tasked with binding and transporting iron in the blood. The structure of transferrin has two carbohydrate side-chains, with sialic acid normally at the end.
If ethanol interferes with the formation of transferrin, the amount of transferrin that contains less sialic acid than normal increases in the blood (carbohydrate-deficient transferrin, CDT).
In order for the S-CDT level to increase, women should have 2–4 units and men 4–6 units of alcohol, which is approximately 50–80 g of ethanol per day, every day for 1–2 weeks.
When should CDT be measured?
CDT should be measured if you regularly use high amounts of alcohol or suspect the possibility of reoccurrence of alcohol abuse. Liver disease, depression, and pancreatitis are possible consequences of high alcohol consumption.
What does a CDT test measure?
CDT measures high alcohol consumption, but it is not enough for diagnosing excessive alcohol consumption alone. Once excessive alcohol consumption has been discontinued, the S-CDT value normalises within 2–4 weeks.
The test indicates the proportion of carbohydrate-deficient transferrin in the total amount of transferrin. Reporting the CDT as a ratio of total transferrin makes it possible to reduce false positives.
How to interpret the CDT test result?
Normally, the result is:
- <1.3% negative
- 1.3–1.6% threshold value
If the result is at the threshold range, the test should be repeated approximately 4 weeks later.
Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.
Read more about defining reference values.
What can cause elevated CDT values?
Elevated CDT values can be a sign of excessive alcohol consumption. The S-CDT value does not increase with occasional use of alcohol; it indicates continuous alcohol consumption. With regard to excessive alcohol consumption, the sensitivity of the CDT test is 73% and the specificity 95%. Sensitivity refers to the proportion of correct elevated results seen in the test out of all subjects with the condition. Specificity, on the other hand, refers to the proportion of correct negative results seen in the test out of all healthy subjects.
High carbohydrate-deficient transferrin (S-CDT) values can also occur in the following contexts:
- Biliary cirrhosis
- Severe liver disease
- Users of antiepileptic drugs
What can cause decreased CDT values?
The CDT level can be low in some people with high alcohol consumption. Blood tests can detect harmful alcohol consumption in approximately four in ten people with high alcohol consumption. High alcohol consumption can also be identified using the AUDIT questionnaire (Alcohol Use Disorders Identification Test).
The most typical additional CDT tests:
- Amylase breaks down starch from food (1078 S-Amyl)
- Alkaline phosphatase is elevated in liver and bone diseases (1046 S-AFOS)
- Bilirubin is formed by the breakdown of red blood cells and is a test for liver and bile duct diseases (1185 S-Bil)
- Gamma-glutamyl transferase is a sensitive indicator of liver diseases (1489, S-GT)
- Alanine aminotransferase, indicator of liver cell damage (1026 S-ALAT)
- Aspartate aminotransferase reacts quickly to liver, cardiac muscle, and musculoskeletal cell damage (1128 S-ASAT)
SYNLAB test list: Carbohydrate-deficient transferrin (4101 S-CDT) https://www2.synlab.fi/laboratoriokasikirja/tutkimuskuvaukset/desialotransferriini/
SYNLAB tests: Carbohydrate-deficient transferrin https://www.yml.fi/tuotekuvaus_show.php?tuotenro=85
Terveyskirjasto health library: Desialotransferriini (S-CDT) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=snk99004&p_hakusana=desialotransferriini
Fasting is not required
This examination does not require fasting