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Ethylglucuronide (EtG)

Ethylglucuronide (EtG) is a conjugate of ethanol (alcohol) and glucuronide (which occurs naturally in the body). EtG is a urine based assay is reported to be sensitive to "any alcohol consumption within the last 24 to 72 hours". The more alcohol consumption the more likely EtG will be positive for a longer period of time. While it is very specific for alcohol the problem is that it sometimes picks up alcohol from sources other than social drinking such as cough medicines, hand washes etc. This is minimized by setting the cut-off appropriately. It is the best choice for picking up anything short of abstinence or monitoring abstinence. We are now performing this in our lab.

Phosphatidyl Ethanol (Peth)

Phosphatidyl Ethanol (Peth) is a conjugation product of ethanol with phospholipids on the red blood cell membrane (blood test). It is not sensitive to very low levels of drinking (say one or two drinks), however becomes more positive with more drinking, but tends to level off and can't as readily distinguish between heavy drinking and moderate drinking. As such, it is good to detect significant alcohol consumption but not really to say that there is continual heavy drinking (see below). It is still more of a research tool but it is gaining more popularity as a clinical tool. We have not yet set up an assay in our lab since it is done at present with an LC-MS method which is very expensive to implement. We can send to a contract lab for measurement, however.

Carbohydrate Deficient Transferrin (CDT, %CDT or %dCDT)

This is an abnormal form (isoform) of the glycoprotein transferrin which is elevated by heavy alcohol consumption. Its use is similar to hemoglobin A1C for diabetes detection and monitoring given that in sensitive individuals percent dCDT goes up and down with heavy drinking and abstinence or reduction in drinking. It is about 60 to 70 percent sensitive (positive) in people who drink at least 4 to 6 drinks per day (about 5 out of seven days a week) and is almost 98 to 100 percent specific (very few false positives with our assay). As such, it picks up drinking levels that are indicated to be harmful to health and that may indicate a more serious alcohol use disorder. We perform the HPLC assay that detects genetic variants and liver problems that might lead to false interpretations (a problem with older immunoassays).

What is EtG? Where Does it Come From?

EtG, or ethylglucuronide, is a byproduct of ethanol (alcohol that one drinks) and glucuronide a common biological compound made in the liver that binds various toxins and drugs in the body that allows them to be excreted in the urine. When someone drinks, even relatively small amounts of alcohol, EtG is formed and can be detected in the urine.

Why is Urine EtG Detection Any Better than a Blood or Breath Alcohol Test?

EtG can be found in the urine much longer than alcohol in the blood or breath. After a few drinks, EtG can be present in the urine up to 48 hours, and sometimes up to 72 or hours or longer if the drinking is heavier.

Can the EtG Amount Indicate How Much Alcohol Someone Has Actually Consumed (i.e. Number of Drinks)?

Not really. While higher amounts of EtG might indicate larger amounts of alcohol consumption, the exact number is influenced by several factors: the amount and when it was consumed. The longer the time since consumption, the lower the EtG level (see above). Also, some people might convert more alcohol into EtG than others and/or excrete it more quickly. Finally, there is a maximum amount of EtG that can be measured, so drinking above that limit might not raise EtG more than can be detected (ceiling effect). It was designed to detect “any drinking”, not heavy drinking. If you wish to detect heavy drinking consider ordering %dCDT (see other information).

Why Do You Report EtG Levels at Two Different Cut-Offs 100 ng/ml & 500 ng/ml?

We do this to provide complete information on which to base a sound clinical decision. EtG can be detected by our assay system at levels even below 100 ng/ml, but we build in a “margin of safety” so that at 100 ng/ml we are very certain that EtG is present, indicating even small amounts of drinking. However, there have been some reports in the literature, as well as concern raised in legal cases, that other sources of alcohol (e.g. mouthwash, hand sanitizer) might cause levels of EtG above 100 ng/ml to be detected in the urine. Although these situations are rare, and hard to replicate under controlled conditions, in those instances where a higher level of certainty is needed (forensic cases etc.) the clinician might want to use the 500 ng/ml cut-off.

Disialo carbohydrate-deficient transferrin (%dCDT) is a blood test for heavy alcohol use that can be very useful in evaluating medical symptoms and predicting complications after surgery. It is based on the fact that an average daily consumption of more than 60g of alcohol (about 5 standard drinks) during the previous 2 weeks increases the percentage of transferrin that has a deficient carbohydrate content. A positive %dCDT test result is 1.7 percent or higher and may change up or down with increased or decreased drinking.

Does a High %dCDT Mean that a Person is an Alcoholic?

No, not at all. Alcoholism is a clinical diagnosis that can only be made with a more complete assessment. There are many people who might be drinking heavily enough to elevate %dCDT who do not meet criteria for alcohol abuse or dependence.

Does a High %dCDT Indicate Harmful Alcohol Use?

The fact that %dCDT is elevated most likely means that a person is drinking too much. %dCDT is an indication that alcohol is disrupting the normal chemistry of the liver cell. While it does not mean that there is liver damage per se it does indicate that alcohol is having a negative effect. It also means that alcohol may be affecting other organs besides the liver and playing a harmful role in the patient’s medical or social functioning.

How Sensitive is %dCDT?

It has been established that %dCDT can increase after about 2 to 3 weeks of steady alcohol consumption of about 4 to 6 drinks a day (this is equivalent to a bottle of wine, 5 cans of beer, or ½ pint (8 oz.) of hard liquor). The longer a person drinks at this level (or perhaps binge drinks) the more likely %dCDT will be positive. Men seem to be more sensitive than women. In many studies, chronic heavy drinking leads to a sensitivity of 60 to 80 percent.

How Specific is %dCDT – Do Other diseases or Drugs Affect it?

Actually, %dCDT is quite specific for heavy alcohol use. There are a few inborn errors of glycoprotein metabolism that may cause elevated %dCDT in about 1 to 5 percent of the population. Also, very severe liver disease may lead to false positives. There are no medications that are known to elevate %dCDT. The new %dCDT test is capable of identifying genetic variants that might cause false positives and negatives as well as unique patterns due to liver disease related to heavy alcohol use.

How Long Does %dCDT Stay Elevated Once a Person Stops or Moderates Drinking?

In most people, an elevated %dCDT will return to normal during several weeks of alcohol abstinence. It will also decrease if a person substantially reduces drinking.

Can %dCDT be used to Monitor How Well People are Doing in Moderating their Alcohol Intake?

Most definitely. Data show that a 30 percent reduction in %dCDT is consistent with a substantial reduction in alcohol intake. %dCDT then has characteristics similar to hemoglobin A1c, cholesterol and other blood tests that change based on diet or pharmacological intervention. If %dCDT goes up again, once it has been reduced, this could be an indication that the person has returned to heavy drinking.

What if a Person Admits to Drinking Heavily but %dCDT is Not Elevated?

There could be several explanations for this. Since %dCDT begins to “normalize” within a few days, if a person has not consumed alcohol for four days or more prior to testing, the %dCDT may have fallen sufficiently to read within the normal range. However, it is well known that a person can have a %dCDT within the normal range and still experience a 30 percent reduction if followed over time while maintaining abstinence. Also, not everyone is a %dCDT responder/elevator. That is why a good clinical history as well as the utilization of GGT may be useful.

Why Assess GGT as Well as %dCDT?

GGT and %dCDT are independent markers of heavy drinking. Alcohol may elevate one, the other or both in different people. It usually takes heavier and more chronic drinking to elevate GGT but in some people, especially women, GGT seems to be more sensitive to sub-acute heavy alcohol use. Also, GGT may increase secondary to other illnesses (ex. hepatic, biliary, obesity), and medications (ex. hormones, anticonvulsants). So if an isolated GGT is abnormal one might need %dCDT to confirm or disconfirm that the elevation is due to alcohol use.

What Do I Tell the Patient if %dCDT is Elevated?

Of course clinical judgment and other signs and symptoms should guide the response. However, a non-confrontational approach such as “it appears that the amount of alcohol you are drinking (not being accusatory of drinking too much) may be affecting how your body functions – we have evidence that alcohol may be disrupting your liver metabolism which also means it may be affecting your other symptoms (fill in the blank as necessary). So… lets see if a reduction in drinking (perhaps in conjunction with other treatments that I might prescribe) may be useful in helping with your problem. Lets make another appointment. Between now and then try to keep a diary of how much you drink each day so we can discuss it more thoroughly.” An appointment for reassessment can be made, the use of a questionnaire (like the AUDIT [see enclosed pamphlet] which takes a few minutes for the patient to fill out) can be considered, and a retest of the %dCDT undertaken. If a person exhibits persistent heavy alcohol consumption, a referral for counseling might be considered).

Is %dCDT Covered by Third Party Payers?

%dCDT is covered by Medicare and Medicaid. Most insurance companies follow the lead of government payers and should cover the expense of testing within the limits of their policies. Even if not covered, the costs of a misdiagnosis of heavy alcohol use are costly to patients and medical personnel.

How Quickly Can I Expect to Get the Results of %dCDT Testing?

It is anticipated that results will be available within 24 to 48 hours of the serum sample reaching our laboratories during Monday through Friday business hours.