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Susan Ivy
Susan Ivy, Nurse (RN)
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I have a blood test coming, and my doc ordered a CDT test

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I have a blood test coming, and my doc ordered a CDT test also. I just want to know how it works. The goal is not to try and rig the results, simply to understand the whole thing. If I'm not mistaken, this is a test done to detect chronic alcool abusers. So, I imagine it would be best not to drink the night before, right? lol But further more, I was told that, if I had a really well wined evening, it may take up to 14 days WITHOUT drinking AT ALL for the results to get back to a more normal count. Not that I find this a difficult length of time without drinking, but I want to know if its true, or if it takes longer... Just to make sure that the results are ok, cause I think its not JUST for that that my doc is ordering the blood tests, and I think it might distract from more important matters: I'm losing sensitivity in my feet and legs. Had a EMG exam recently, awaiting for the results, but I also have Thyroid gland problems and anemia, lack of B12.... Anyhow, whats the thing with the CDT tests?
Hello and Thank You for using JustAnswer Health for your question.

As you mention, the CDT (Carbohydrate Deficient Transferrin) test is for the purposes of detecting heavy alcohol abuse - more than 5 drinks per day. It can show heavy chronic alcohol abuse up to 2 to 4 weeks after stopping. So my 'educated guess' is that if you had one evening of where you had up to 5 glasses of wine within 4 weeks of the test - there might be a tiny bit of elevation - but not a significant amount of elevation.

This test has become possible due to knowledge gained in cell biology and is not easily explained, but I will try, and also refer you to my sources for more details.

Transferrin is a molecule made of sugar and protein produced in the liver and it's purpose is to 'transfer' iron molecules from the intestine to the blood stream to go to the cells and organs that need the iron to function.. Normal transferrin carries sugar molecules along with it like, little side cars. When one drinks alcohol at the rate of about five drinks a day, the liver does not manufacture transferrin in the normal way - some of the side cars are 'knocked off' or eliminated. Thus, the transferrin molecule becomes deficient in sugar side-chains. In other words, the transferrin molecule becomes carbohydrate deficient or, with the words rearranged - carbohydrate deficient transferrin (CDT)

Under normal conditions (which allows for an occasional drink) only about 1 to 2% of transferrin is carbohydrate-deficient. After heavy drinking, the transferrin levels can become as high as 10% deficient of carbohydrate. Studies have found a CDT of 2.6% and higher to be indicative heavy drinking; 50 to 70% of heavy drinkers were found to have a CDT greater than 2.6%.

There is not much that can result in false positives for this test - for example only something like end stage liver disease or very advanced liver disease could result in a false positive - and your doctor should have already checked you for this, and you would also likely know as you would have symptoms like jaundice, fatigue, bloated abdomen, etc.



or company manufacturing test:

I hope this helps, but please reply if you still have questions so that I may continue to assist you until you are happy with your answer.
Customer: replied 6 years ago.

Thank you for your answer, it was most complete! =)

But I'm now a bit worried, cause that well winned dinner was following a period of 4 days without drinking, but before that, I was on a 2 week vacation at an all-included sunny destination, and 5 drinks a day was definitely the norm... Do you think there might be a chance that a 2 week break (definitely welcomed by my liver I'm sure, as I have a bad one: I take 1 200 mg advil and I feel bused, I've always been hyper-sensitive to medications and such) might be enough to get the numbers back to a reasonable level??

Hello and thanks for replying with your follow up questions.

Was the two week vacation within the 4 week period before the test will be done?

If so it will likely show some elevation, but not as much as it would if your were still continuing to drink that much. I am sorry i can't be more specific than that - but from what I have read, the CDT will show a period of heavy drinking for anywhere for 2 to 4 weeks - so you may be lucky and not show the effects, but then again, you may very well show some elevation if it was during the last 4 weeks that you were drinking this amount.

I think it best to take out a calendar and mark the days with the drinking and simply show it to your doctor and try to be as upfront and honest as possible, as you have been with me.

The Advil should not effect the test from what I understand.

Tylenol is a medication that can elevate liver enzymes, but this test is not checking for elevated liver enzymes.

Also, for your future well being, I should let you know some information, that unfortunately many people do not know, but I worked for 7 years on a long term study of women, children and alcohol, and was made well aware of these details.

This is not related to the upcoming CDT, but just info. that I am giving you so that you will be aware of the amounts of alcohol that are now considered safe, especially for women, to drink. Damage to women's livers in general occurs at a much lower level than what it does for men. This is because women process alcohol via a different enzyme processing pathway than men. In fact, 1 drink for a women is equivalent to 2 drinks for men, as far as the amount of damage it causes the liver physiologically. Thus, the recommendations for amount of alcohol that can be drunk safely, is much lower for women than men. Drinking more than 1 alcoholic beverage per day for women can lead to damage, whereas for men, drinking more than 2 alcoholic beverages per day can lead to damage. Thus it takes much less alcohol to create some long term damage than many people realize. The manufacturers of alcohol certainly don't make this fact apparent, and neither does our television or film industry, as they often show people drinking alcohol all day long without any consequences at all.

Again, I hope I am not confusing the issue, but I have found so many people unaware of the parameters for 'safe' drinking as far as the long term physical effects. Some of the effects of the alcohol on the liver can be partially remedied by making sure to eat protein (helps rebuild the liver) the day after drinking, as well as supplementing with the B vitamin Thiamine (prevents alcoholic dementia - as alcohol depletes the brain of Thiamine).

I think health care providers need to do a better job of getting the facts out about alcohol and how damaging it can be, because there are many people such as yourself that think 5 drinks a day on vacation or weekend is not a problem, when indeed it can be quite harmful to the system, especially in women.

Let me know if you have more questions.

Customer: replied 6 years ago.

I thank you very much for your additional info and the true care you are showing. It is greatly appreciated.

I will be accepting your answer, but I just want to know: what amount is considered "a drink" if we're talking about wine?

It would be considered one regular glass of wine. It is said that whether a beer, a mixed drink, or a glass of wine, typically they are all comparable in the amount of alcohol. I know that in reality that may not always be true, because a person may have a type of wine or beer that is higher in alcoholic content than another, but in general a regular size glass of wine that is of average alcoholic content that is filled usually 1/2 to 1/3 full, if I am correct.
Customer: replied 6 years ago.
about what, 125ml? 250ml?
The sources I looked at say from 4 oz (120 ml) red wine to 5 oz or 148 ml. Wine coolers or beer - 12 fl ounces or 355 ml. For 'spirits' one shot = 1.5 oz or 44 ml.
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Customer: replied 6 years ago.
Say, I forgot to ask something last time: I'm back from my "BIG drinking 2 weeks" for 5 days now. If, say tonight, (so less than 2 weeks before my boold test, I have 1 or 2 glasses of wine (its my friends birthday tomorrow), does it put the counter back to the start, or can I have 1-2 glass with a meal before the 2 weeks period?
Hello. According to the information about the CDT only large amounts of drinking (5 drinks per day or more) are shown by the test results, so it should not make a difference on the test to have 1 or 2 glasses.
Customer: replied 6 years ago.
Even if its not been 2 weeks yet since I last had a 5+ drinks/day period?
I may not be following your logic, sorry! Apparently the protein only becomes carbohydrate deficient (which is what the test looks for) when a person is drinking a large amount of alcohol, which for this test is 5 drinks or more per day. So as long as you keep it well under 5 drinks per day, according to what is said about the CDT test and how it's results are determined, it should not further effect the results.

That being said, we do know that drinking 2 or more is not good for the liver in women, even if it doesn't show up on the CDT test, so i would suggest drinking 1 or 2 a day at the very most (actually only 1 drink per day is recommended for women)
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Customer: replied 6 years ago.

lol sorry, I know I'm hard to follow sometime =) I just thought that there was a 2 weeks minimum WITHOUT ANY alcohol for the rates to go down and that, until the minimum of 2 weeks to lower the rates was past COMPLETELY without alcohol intakes, the liver might still be fooled into thinking it needed to continue producing those abnormal transferrin...

No, that is not how the test works. It takes an excessive amount of alcohol intake to show the results.
Customer: replied 6 years ago.

I see.

WEll, that definitely answers my question, and I thank you again for your patience with me! =)

You are very welcome. I hope all works out well! Feel free to update me when you get your results.