In a CBR alcohol referral, a doctor looks at a combination of blood values, not a single number. The most common set is gamma-GT, CDT and MCV. If all three are elevated, that fits a pattern of chronic excessive use. A separate test beforehand gives you insight into where you stand.
Many people searching for this have an investigation into driving fitness ahead of them. Below you will read which values count and how far back they look.
What does the CBR driving-fitness investigation involve?
The investigation into driving fitness is an assessment the CBR can impose after, for example, being stopped with too much alcohol. An independent doctor combines an interview, a physical examination and blood testing. The outcome determines whether you keep your licence, and under what conditions.
The result of a single test does not decide the procedure on its own. You can, however, see beforehand with your own measurement whether your values fall within the reference range.
Which blood values count for alcohol?
The doctor usually looks at a set of markers together. A frequently used combination is gamma-GT, CDT and MCV.
- CDT (%CDT): reference below 2.8%, looks back about two to three weeks, and is the most specific marker for alcohol.
- Gamma-GT: a liver enzyme, reference roughly 10 to 40 in men and 6 to 25 in women.
- MCV: the average size of red blood cells, which can be elevated after prolonged heavy use.
A fuller explanation of these markers is in our overview of proving alcohol use. If you only want your CDT value measured, a CDT test for alcohol can quantify that for you.
How far back does CDT look?
CDT looks back about two to three weeks and responds to a pattern, not a single drink. The half-life is around 14 to 17 days, so with abstinence an elevated value usually falls within a few weeks. An elevated value can also have other causes; you can read more at CDT too high.
Every blood test result at Zuivertest includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
Sources
- Jellinek, "Which blood tests does the CBR use?" (jellinek.nl)
- Richtlijnendatabase, "Laboratory testing for alcohol misuse in driving-fitness assessments" (richtlijnendatabase.nl)
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