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 24-72 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) 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 %dCDT goes up and down with heavy drinking and abstinence or reduction in drinking. It is about 60-70% sensitive (positive) in people who drink at least 4-6 drinks per day (about 5 out of seven days a week) and is almost 98-100% 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).