Pennsylvania Hospital of University of Pennsylvania, Philadelphia (Drs. Chaudhari and Nunes); Henry Ford Hospital, Detroit, MI (Dr. Moonka) frederick.nunes@pennmedicine.upenn.edu
The authors reported no potential conflict of interest relevant to this article.
CDT is approved by the FDA as an assay for alcohol consumption.37 While CDT is felt to be one of the better indirect markers of AUD and can extend the window of detection, there are still issues with its sensitivity and specificity.38 This biomarker can be elevated with other liver diseases and can be affected by the patient’s age, body mass index, gender, and tobacco use.39,40 Testing for CDT has never achieved widespread clinical use and has been largely supplanted by the more accurate PEth test (described in a bit).
Direct biomarkers offer insight into recent alcohol use
Other than ethanol itself, direct biomarkers of alcohol use are minor ethanol metabolites created through biochemical reactions when ethanol is coupled to endogenous compounds. Hence, the presence of these metabolites is usually directly related to ethanol consumption.41 Direct alcohol biomarkers are EtG, EtS, FAEEs, and PEth (TABLE 223-31). They reflect alcohol consumption over a period of several days, making them useful when paired with questionnaire data, especially for identifying young adults who engage in binge drinking.42
Ethanol can be measured in blood, urine, and breath and is detectable a bit longer in urine than in blood. However, alcohol is detectable in the blood only for 6 to 12 hours after drinking. After alcohol consumption, concentrations peak in the blood within 2 hours. The window for detecting ethanol in the blood depends on the amount of alcohol consumed and the elimination rate of alcohol, which is about 12 mg/dL/h (or 0.012%)—approximately the same amount of alcohol contained in a standard drink (14 g).
EtG can be detected in urine for ≥ 24 hours after just 1 or 2 drinks, and for up to 4 days after heavy consumption.
Checking the blood alcohol level might be helpful in the office if a patient appears intoxicated but denies alcohol use. A blood alcohol level > 300 mg/dL, or > 150 mg/dL without gross evidence of intoxication, or > 100 mg/dL upon routine examination indicates AUD with a high degree of reliability.33,43 But the short half-life of ethanol in blood limits its use as a biomarker,33 and it is not a good indicator of chronic drinking.44
EtG and EtS. Less than 0.1% of ethanol is secreted as the metabolites EtG and EtS, which are generated, respectively, by the enzymes uridine diphosphate glucuronosyltransferase and sulfotransferase.45 They have value in the diagnosis of AUD because of the length of time in which they can be detected. Urinary EtG and EtS have been especially important biomarkers for monitoring relapse in outpatients treated for alcohol-related problems.46 Generally, EtG and EtS can be detected in urine for 13 to 20 hours after a single drink (0.1 g/kg), and for up to 4 to 5 days following ingestion of large amounts of alcohol.47
