Biomarkers for Alcohol Use and Abuse: A Summary

Clinicians can use several biochemical measurements to objectively assess patients' current or past alcohol use. However, none of these currently available biomarkers--including measures of various liver enzymes and blood volume--are ideal. Several more experimental markers hold promise for measuring acute alcohol consumption and relapse. These include certain alcohol byproducts, such as acetaldehyde, ethyl glucuronide (EtG), and fatty acid ethyl esters (FAEE), as well as two measures of sialic acid, a carbohydrate that appears to be altered in alcoholics. Some progress has been made in finding markers that predict people's genetic predisposition to alcoholism, such as genetic differences in several neurotransmitters, including beta-endorphin and gamma-aminobutryic acid (GABA). KEY WORDS: screening and diagnostic method for AOD (alcohol and other drug) use; pattern of AOD use; alcohol-related biological markers; alcohol-related biochemical markers; alcohol-related genetic markers ********** To treat people with alcoholism adequately, clinicians need tools that can properly assess not only the extent of the patients' recent and past drinking activity but also any family history of drinking problems (i.e., genetic predispositions to alcohol abuse and alcoholism) they may have. A good case history is certainly a start, but more objective measures also are important. Biochemical substances in the body that can indicate the presence or progress of a condition, or any genetic predisposition toward it, are called biomarkers. There are two kinds: state markers and trait markers. State markers are biochemical measures that tell clinicians something about people's recent drinking patterns, including whether they have a history of heavy drinking and whether they have had a recent binge or even just a few drinks. Trait markers are biochemical markers that reveal something about a person's inherited risk of abusing alcohol. A good biomarker, whether state or trait, should be sensitive--that is, accurate for most if not all drinkers, not just a subset--and specific, or linked to alcohol use but not other illnesses or problems. The test used to measure the biomarker also should be precise and accurate. (For definitions of terms central to this article, see the accompanying Glossary.) This article presents an overview of current alcohol biomarkers. Although some of the markers described here have been in wide use for many years, some are new and under development. The goal is to compile a large toolkit of biomarkers that can provide objective, quantitative data to clinicians as they evaluate patients. STATE MARKERS When clinicians evaluate a patient's history of alcohol consumption, they want to know not only about recent (i.e., acute) drinking patterns but also about long-term (i.e., chronic) drinking patterns and whether that drinking has been moderate or heavy. (Heavy drinking is defined in this article as consuming more than 60 grams of alcohol--between four and five drinks--a day, unless otherwise noted. Consuming this amount for 2 weeks or more is considered to be chronic heavy drinking.) The various state biomarkers use several techniques to assess different levels or periods of alcohol consumption. These markers may be related to chemicals produced when the body breaks down, or metabolizes, alcohol or may reflect changes in other compounds, cells, or tissues that result from chronic or acute alcohol exposure. (The table summarizes the sensitivity, specificity, and potential uses of these measures. For further information on state markers, see the figure.) Currently Used State Markers For many years, clinicians have had access to a group of biomarkers that indicate a person's alcohol intake. Several of these reflect the activity of certain liver enzymes: serum gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and carbohydrate-deficient transferrin (CDT), a protein that has received much attention in recent years. …