Carbohydrate Deficient Transferrin (CDT) DVLA Blood Test

The Carbohydrate Deficient Transferrin (CDT) test measures a particularly sensitive biomarker that tracks heavy alcohol consumption over an extended period of time. Transferrin is a protein which carries iron to parts of the body that need it. Drinking too much alcohol can cause an increase in certain types of transferrin which are deficient in carbohydrate. If an individual drinks steadily and heavily (4-6 units of alcohol per day) for several weeks the percentage of transferrin which is deficient in carbohydrate will rise. The longer a person drinks at this level, the higher the level of CDT.

Intermittent or binge drinking can also increase CDT levels. The extent to which this occurs is dependent on the frequency of binges and the amount of alcohol consumed on each occasion. Elevated CDT will decline with reduced alcohol consumption and will revert to normal after several weeks of abstinence.

This test has a very high level of specificity (i.e. it is not affected by other drugs or substances) and therefore it has been adopted by the Secretary of State's Honorary Medical Advisory Panel as the sole test for assessing harmful use of alcohol for high risk offenders.