This Postal CDT Test (Carbohydrate Deficient Transferrin) is a home blood test used to check if a person has been drinking excessive quantities of alcohol over the previous 7-14 days.
Please note that this CDT test is a blood test done at home and sent to the laboratory to be processed to get a result. It does not give you instant results at home.
CDT is a normal protein in the body and is present in all people. It only becomes elevated when a person drinks excessive amounts of alcohol regularly or even with binge drinking.
A CDT test is used by the DVLA when a person applies for their driving license to be reinstated. The DVLA accepts a CDT cut-off level of ≤ 2.2 %. A CDT test is also used by companies, such as Transport for London (TfL), who want to make sure an employee is not drinking excessively.
In our experience, the DVLA CDT tests can cause a lot of anxiety. Many of our clients order a CDT test for for their own piece of mind before they attend for their official DVLA assessment.
Alcohol in urine or blood can only be detected for 24-48 hours. Therefore, a CDT test is a better test for alcohol misuse because it checks a longer time-frame. An Alcohol Profile test is even better because it checks for changes in the blood and liver to assess if the excessive drinking has damaged the body in any way.
The Postal CDT Test kit contains all you need to take the blood sample at home and send it to the laboratory for processing. The CDT blood sample is taken by pricking your finger with a small sharp lancet, the same type of small needles that are used by diabetics when they are checking their blood sugar. Please watch this video showing how this is done, before trying to collect the sample. Only a small amount of blood is needed.
Check that your address details are correct at the time of ordering the test. A Postal CDT Test kit containing clear instructions and testing equipment will then be posted to you by 1st class Royal Mail.
Please note that home tests are for personal use only. We cannot provide assurance to an outside agency that the test belongs to a particular individual. Assurance can only be provided when doing the test at Patient Reception in London when accompanied by a photo ID of the person being tested.
Results take 5 working days * once the sample reaches the laboratory and will be emailed to you. They include a doctor's explanation of the results. Please note that we do not give out results by telephone as this information is confidential and there is no way of identifying a caller.
Clients should order their home test kits at least 2 weeks before they need the results to avoid potential problems.
* Indicative timings only. Actual result may be earlier or slightly later.
Often combined with a liver function blood test to check for any damage to the liver from excessive alcohol consumption.
1. Alcohol Misuse (A 19 out of 20 chance): i.e. by far the most likely cause of a high CDT.
2. Liver Disease: Certain liver problems which cause a blockage or damage to bile ducts; e.g. primary biliary cirrhosis, primary sclerosing cholangitis, gallstones or liver/pancreatic cancer. These causes can be excluded if liver function tests (LFTs) are normal.
3. Transferrin Variants: Transferrin is a protein used to transport iron and can undergo changes by the consumption of alcohol. The normal type is C. People who have type D may have a raised CDT. Type D is rare in Caucasians but may be present in 10% of Africans. People with this variant cannot use CDT to check for alcohol misuse because CDT will always be high. We would recommend that these clients use a urine EtG test instead.
4. Carbohydrate deficient glycoprotein syndromes: these are very rare syndromes resulting in mental retardation in children.
You need to drink the equivalent of 100-150g of alcohol per day to raise CDT levels. This equates to 5 pints of beer, a bottle of wine, or one-third of a bottle of spirits daily.
Intermittent or "binge" drinking can also raise CDT levels. This would have to be in the range of 200-300g of alcohol on two occasions per week (around double the above amount) and no alcohol on the other days. Just one day of excessive drinking with the other days of no alcohol would probably not be enough to raise CDT levels over a 7-14 day period.
Defined in terms of the alcohol-related driving convictions below, the courts notify the DVLA of high risk offenders.
An independent medical examination will be arranged when an application for licence reinstatement is received by the DVLA. The assessment includes:
If a licence is awarded, the ’til 70 licence is restored for Group 1 car and motorcycle driving. Consideration may be given to a Group 2 licence.
If a high risk offender has a previous history of alcohol dependence or persistent misuse but has satisfactory examination and blood tests, a short period licence is issued for ordinary and vocational entitlement but is dependent on their ability to meet the standards as specified.
A high risk offender found to have a current history of alcohol misuse or dependence and/or unexplained abnormal blood test results will have the application refused.
The high risk offender scheme applies to drivers convicted of the following:
1. Enter the name and date of birth of the person taking the test at the top of the page. These details are essential to uniquely identify your sample by the laboratory and you will be unable to proceed further without them.
2. Pay online by credit or debit card
3. Initially, you will receive an automatic reply to confirm that we have received your order.
4. Your test request will then be processed between 9am-5pm, Monday-Friday, and your postal test kit posted by 1st Class Royal Mail.
5. Your home test kit will contain everything you need to do the test including testing equipment, instructions, a Pathology Request Form and a postage-paid envelope to return the sample to the laboratory.
6. Once completed, place your test sample in the postage-paid envelope. Make sure to also include the Pathology Request Form with your sample. This instructs the laboratory which test to do. Failure to include this form will invalidate the test.
8. Results will be sent by email as soon as they are available.
All laboratories need information regarding the client to identify their individual sample.
Without these details, tests cannot be done.
The minimum requirement is the full name and date of birth.