CBR tests alcohol use privately not for psychiatrist

CBR tests your alcohol consumption

This involves a complete blood test like the one the CBR performs to check your alcohol use in the past period. This test looks back at your alcohol consumption by about 3 weeks.

CBR's blood test looks for elevated values that indicate excessive alcohol consumption. The following blood values are involved:

• GAMMA-GT (GGT)
• %CDT*

*Separate clotting tube is not needed because in this study all tests are done in the same lab.

If you have been drinking alcohol regularly recently, the blood test may show this. This may result in invalidation of your driver's license.

CD-Tect Carbohydrate Deficient Transferrin (CDT)

CDT is a type of protein that is produced when excessive alcohol is consumed over a period of at least a week. The CDT percentage in blood increases as more alcohol is consumed. With abstinence, CDT usually drops to normal within two to three weeks, but after long-term alcohol consumption, this normalization can take much longer.

Measurements for the purpose of testing fitness to drive in the context of alcohol abuse are carried out in specialised laboratories. Since 2019 the results of the permitted methods are all standardised, i.e. traceable to IFCC HPLC reference methods and therefore provide comparable results for the same sample. The recommended upper limit of 1.7% with an uncertainty of measurement of 0.3 percentage points and the cut-off point of 2.0% are used for forensic use, including investigation of fitness to drive. The cut-off point of 2.0% is therefore the highest value that can still occur in a normal population (obviously taking into account the measurement uncertainties).

Proteins often have sugar groups, which are necessary for their recognition and function. The characteristics of blood groups, for example, can be traced back to different types of sugar groups on the membrane of red blood cells. Also the iron transporter protein transferrin contains two characteristic carbohydrate chains, which together contain on average four so-called sialic acids.

Under the influence of a degradation product of alcohol (acetaldehyde) a transferrin form arises where one or both carbohydrate chains are absent: we then speak of carbohydrate deficient transferrin or CDT. The CDT is reported as a % of total transferrin to cancel out the effect of fluctuations in transferrin levels, for example, a rising transferrin in iron deficiency.

The Centraal Bureau Rijvaardigheidsbewijzen (CBR) also requests specific laboratory tests in certain cases for persons apprehended with alcohol use in traffic as part of a psychiatric assessment of fitness to drive (see the CBR website). Traditionally, tests related to liver function (gGT and ALAT) and average red blood cell size (MCV) were requested. Currently, the measurement of the percentage CDT is the most important laboratory parameter when excessive alcohol consumption is suspected.

How reliable is the %CDT and at what alcohol consumption is it elevated?




It should be noted that no laboratory test in chronic excessive alcohol consumption always gives an abnormal result, or in technical terms: no method has a sensitivity of 100%. Conversely, with no or minimal alcohol consumption the results should be normal, but exceptionally false elevations can also occur. In technical terms, no method is 100% specific.


Scientific research has shown that the %CDT is overall the best laboratory parameter for demonstrating chronic excessive alcohol consumption. The applied upper limit for CDT corresponds in men to the consumption of an average of about 60g of alcohol per day (roughly 1.5L of beer or 1 bottle of wine per day) for at least one week. Intake of more than 60g of alcohol per day will cause serious organ damage in the long term. For women this limit is about 40g per day.

In the Dutch NVKC guideline, which deals with alcohol consumption, 2.0% DST is used as the cut-off point. With results higher than 2.0% it can be said with great certainty that the result does not belong to the normal distribution.

Increased CDT in the serum occurs after an average daily consumption of more than 60 g of alcohol over a period of about two weeks. With a consumption of 100 - 400g ethanol/day the CDT value is normally greater than 4%. After cessation of alcohol consumption, the CDT concentration is still detectable for 2-4 weeks, depending on the amount of alcohol ingested. False positive results may occur in persons with severe liver disease, such as primary biliary cirrhosis or chronic active hepatitis.

In addition to the CD-tect %CDT, the following tests are performed by CBR to monitor recent alcohol consumption: GGT, ALAT, ASAT, Blood count incl. MCV

Gamma-GT

Gamma GT (GGT) is an enzyme made in the liver that helps convert and digest substances that enter the body through food and drink. Normally, the concentration of GGT in the blood is very low, but when the liver is under heavy stress, the amount can rise considerably. This happens when the liver is supplied with a lot of substances to process in a short period of time, for example with (extreme) use of medicines or alcohol. GGT will also rise if the bile ducts are blocked, if there are gall bladder problems, or as a result of liver damage.

ALAT, ASAT and blood count are no longer needed in 2022.

What methods can be used for CDT according to the CBR?

As of 2013, the following methods are approved by the NVKC for CBR inspections:

• the N-Latex CDT method from Siemens (upper limit normal 2.2%, cut-off point 2.6%)
• the Analis CE method (upper limit normal 1.5%, cut-off point 1.9%)
• the RECIPE HPLC method (upper limit normal 1,6%, cut-off point 2,0%)
• the HPLC method of BioRad (upper limit normal 1.5%, cut-off point 1.8%)
• the Sebia CE method (upper limit 1,4%, cut-off point 1,7%)
• the HPLC method according to Helander (upper limit normal 1,7%, cut-off point 2,0%)

Blood Values Test uses the Sebia method for this study and on the lab report we use the upper limit of 1.3% just to be sure.

The margin between upper limit normal and cut-off point can be considered a kind of "gray area". This margin includes both the biological distribution within a person and the differences between laboratories. Above the cut-off point it can be said with 95% certainty that a single measured CDT result no longer belongs to the results of a group of normal people. Each method has its own upper limit and cut-off point. Therefore pay attention to which method was used to measure CDT.

As confirmatory (or confirmation) study, only the HPLC method according to Helander is the appropriate method.