CDT Blood Test

Carbohydrate Deficient Transferrin Blood Test

  • Carbohydrate Deficient Transferrin (CDT) is a biomarker for heavy alcohol consumption.
  • Used by the DVLA in its fitness-to-drive test for high-risk offenders.
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What is Carbohydrate-deficient transferrin (CDT)?

Carbohydrate-deficient transferrin, known as “CDT,” is a blood test to detect excessive alcohol consumption (five or more drinks of alcohol per day) over the past two weeks. This test is an objective way to screen and monitor clients.

This test is useful for those who are about to undertake the DVLA medical prior to the return of their licence following conviction and they want to make sure that they will pass. A CDT blood test can also be used as proof that they have ceased or reduced their alcohol consumption.

CDT blood tests are a measurement of a particularly sensitive biomarker. The test can track heavy alcohol consumption over an extended period of time. If an individual drinks regularly, then the percentage of transferrin, which is deficient in carbohydrates will rise. The longer the person drinks, then the higher the level of Carbohydrate Deficient Transferrin. Transferrin remains in the circulatory system for 7 to 14 days and CDT, therefore, can give an indication of alcohol consumption over this period of time. This test gives it an advantage over blood or urine alcohol measurements which only remain elevated for 24-48 hours after alcohol consumption. Elevated CDT levels will reduce in line with the quantity of alcohol consumed.

Intermittent or binge drinking can also increase the level of CDT. The extent to which this occurs is dependent on the frequency of consumption and the amount of alcohol consumed on each occasion.

Carbohydrate Deficient Transferrin levels will then revert to normal after several weeks of abstinence.

This test 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. CBT testing also forms part of the DVLA medical following a Drink Drive conviction.

The CDT blood test is used by the DVLA in its fitness-to-drive test for high risk offenders. The test is very specific and is not affected by other drugs or substances.

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