Alcoholism: Carbohydrate Deficient Transferrin Test Part 1

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Dr. Linda Austin: I’m Dr. Linda Austin. I’m interviewing Dr. Ray Anton who is distinguished university Professor of Psychiatry in the behavioral sciences, and is quite a national expert on substance abuse. Today we’re going to be talking about the detection of alcoholism, and in particular, I want to focus on a biological marker, a test actually, that doctors can order, called carbohydrate deficient transferrin, or CDT. Dr. Anton, tell us about CDT. What, exactly, is it? Dr. Ray Anton: Well, first of all, let me say that the importance of a biological marker is for use in detecting heavy alcohol use. It’s quite important because oftentimes people don’t understand or know how much they actually drink. And if they do, for various reasons, they don’t report it accurately to the people around them, including their primary care physician and other healthcare providers. So it’s very important for us to find blind tests that assist healthcare providers and provide feedback to patients about their alcohol use. Carbohydrate deficient transferrin, or CDT for short, is actually an abnormal transfer in protein circulating in the blood. And I’ll tell you a little bit more about what transferrin does in a minute. Transferrin is a naturally occurring chemical that’s made by the liver and it circulates in our bloodstream. As the blood passes through the digestive tract or the gut, it picks up iron which is a normal mineral in our diet. It’s in things that we eat, and it transports this iron to other organs of the body, in particular, the bone marrow where red blood cells are made that carry oxygen in our circulatory system. And iron is very important for that. So, transferrin, made by the liver, into the blood, picks up the iron, delivers it to the bone marrow and other organs that need iron to work properly, almost like a little factory, a little shuttle for iron that moves around the bloodstream. Well, when people drink on the order of about four to six standard drinks a day, and we can talk about what standard drinks are in a little bit, this transferrin molecule, this little shuttle, isn’t made appropriately. The transferrin molecule typically is made up of a backbone of chemicals called amino acids and attaches to these amino acids or sugar groups, like glucose, the typical sugar that we have in our diet. So, it’s called, in technical terms, a glycoprotein, meaning a sugar-based protein. And when people drink heavily, four to six drinks a day, or more, the sugar groups are not attached onto the amino acid or protein backbone. Another name for sugar groups is carbohydrates. When carbohydrates of sugar groups are not on the transferrin, it’s called carbohydrate deficient or lack of carbohydrate transferrin, carbohydrate deficient transferrin. So it’s a different type of transferrin shuttle molecule than we normally have, and it’s very specific for alcohol. It’s only when people drink heavily that they get this abnormal form of transferrin molecule. We can then collect blood, bring it to the laboratory and, through some sophisticated techniques, separate out this CDT, or carbohydrate deficient transferrin, from normal transferrin, and you get a percent. We actually express it in percent, percent of CDT, which is really the percent of abnormal transferrin that is occurring in the blood. Dr. Linda Austin: You mentioned for to six drinks per day. I’m assuming that’s seven days a week. Now, is it that you begin to get low levels of this CDT at that level and then it increases as you drink more? How does that relationship work? Dr. Ray Anton: Well, that’s a very good question. Under normal conditions, there is a small percentage of this abnormal CDT in the bloodstream, generally. It doesn’t change very much for most people, except when they drink heavily. And then it goes up. That occurs in about 60 or 70 percent of people; not everybody has this abnormal transferrin reaction to alcohol. It may be based in genetics or some other issues in their diet. We don’t know all of the specifics; it doesn’t occur in everybody. But almost everybody who has an elevation in CDT, 96 percent of the time, it’s due to heavy alcohol consumption. Dr. Linda Austin: So then, at what level of drinking do you begin to see the increase? Is it at that, roughly, five drinks a day, seven days a week, or would you see it even, potentially, lower than that? I’m thinking, for example, about people who, certainly, could be called alcoholics, who may have binges, let’s say, seven drinks, two or three days a week. Would that be enough to show up on that test? Dr. Ray Anton: That’s an excellent question. And, unfortunately, the information I’ll provide you, which I will in a minute, is really based on considerable natural observation and looking what we would call backwards, or retrospectively, in studies that are done. And the reason is very simple. You can’t take humans and prescribe for them to drink certain amounts of alcohol, particularly at high levels, and have it be an acceptable type of research. So it’s very hard to distinguish exactly where the cutoff in drinking is. But it’s somewhere on the order of probably about four to five days, out of seven days, of drinking at that level, four to six drinks, at least, a day. So, to answer your question specifically, you have somebody that binges on the weekend, for instance, on a Friday or Saturday night, and may drink 7, 8, 10, 12 drinks, and people do that, believe it or not, and if they only drink two days a week, the likelihood of their percent CDT being elevated is not that great. But as they start moving more towards drinking at that level, say, four times a week, or five times a week, it’s likely to be elevated. Dr. Linda Austin: And then the more they drink, the higher it goes? Dr. Ray Anton: Well, it’s seems to be somewhat of an all-or-none phenomenon. In scientific terms, we say that things are correlated, meaning that one measure is associated with another measure; it’s called correlation. And a perfect correlation would be one, meaning that every time you do one thing, the other thing happens. Well, we have correlations with drinking of about .2 or .3, which is not very high. That means that the more people drink to a certain point, they get more carbohydrate deficient transferrin. But there seems to be a level at which that stops. And it seems to be more, almost, an individual phenomenon. Dr. Linda Austin: Once a person has become abstinent, has stopped drinking, how long does it take for the test to become normal again? Dr. Ray Anton: That’s another very excellent question. And we do have research on that, because we can follow people from the time of drinking through various times of abstinence. You can do what we call going forward, or prospectively. Basically, the average is somewhere between 7 and 14 days. But we’ve had other people that may take as long as three to four weeks to become completely normal. And it somewhat depends on how high the level was when they started, when you first obtained the value close to drinking. So, it does vary a little bit, but typically an average of about a couple weeks, which then allows it to be used to follow people’s progress. You know, if they come in for treatment and the expectation is that they be abstinent, you can take another blood test in two to four weeks and see if the value has fallen and then use that in feedback in treating them. Dr. Linda Austin: Dr. Anton, I want to question you about how physicians are using this clinically, but let’s save that for another podcast. Thank you very much. Dr. Ray Anton: Okay. Thank you. If you have any questions about the services or programs offered at the Medical University of South Carolina or if you would like to schedule an appointment with one of our physicians, please call MUSC Health Connection: (843) 792-1414.

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