Using biomarkers to quantify problematic alcohol use
Direct biomarkers detect alcohol even in small amounts shortly after ingestion. But which one is nearly 100% specific for alcohol use?
PRACTICE RECOMMENDATIONS
› Use a quick screening instrument such as the single-question tool or the AUDIT 1-3 to objectively determine whether patients’ drinking is risky for themselves or for others. C
› Suspect alcoholic liver disease if the ratio of aspartate aminotransferase to alanine aminotransferase is > 3. C
› Consider using the PEth assay in high-risk patients to differentiate between heavy alcohol use and social drinking. C
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
EtG has been detectable in urine for ≥ 24 hours following only 1 or 2 drinks, and for up to 4 days following heavy consumption.48 Shortly after alcohol intake, even in small amounts, EtG is detectable. Analysis of EtG in urine is helpful in monitoring alcohol consumption during withdrawal treatment, for workplace testing, and to check for abstinence in legal matters. The EtG urine test is useful in detecting alcohol consumption in a person who claims to be abstinent but who drank 2 or 3 days before the evaluation. Although accurate, EtG’s window for detection is narrower than that of the PEth assay.
EtS is a good marker of acute short-term alcohol use, up to 12 hours in the blood (or longer in heavier drinkers) and up to 5 days in urine.49 Its sensitivity is highest in heavy drinkers. Post-sampling formation and degradation of EtS have not been known to occur in urine samples. Testing for this second metabolite of ethanol can slightly improve the sensitivity and specificity of the EtG test. A urine test for EtS has a wider detection window. But it has little practical advantage compared with EtG.50
For better clinical specificity, a combination of both EtG and EtS testing has been recommended. However, the EtS assay is more cumbersome and provides little advantage over EtG. EtG values do not correlate precisely with the amount or frequency of ethanol use, but the magnitude of the EtG finding roughly corresponds to the amount of alcohol recently consumed.
False-positive and false-negative results for EtG and EtS are uncommon in practice. However, false-positive results are possible with the EtG test in certain circumstances: presence of Escherichia coli in the specimen, use of ethanol-based hand sanitizers (> 20 times a day) or mouthwashes, and the consumption of substances like pralines, nonalcoholic beer, pharmaceutical products, and fruit juice. Similarly, false-negative results of EtG can occur from degradation if the samples are contaminated with other bacteria, transported without cooling, or stored improperly.51 In practice, this is uncommon, and the test is believed to be specific with few false-positive results. Commercially available EtG colorimetric test strips permit on-site analysis of urine samples.
FAEEs are a combination of different esters and products of alcohol metabolism through a nonoxidative pathway. They are formed by esterification of endogenous free fatty acids and ethanol in blood and several tissues.29 These are sensitive and specific markers of alcohol ingestion and can differentiate chronic alcohol consumption from binge drinking.29 It is elevated for up to 99 hours in heavy alcohol drinkers.30 It can be detected in hair for a longer period than in blood.52 Detection of FAEEs in meconium can help establish fetal alcohol exposure.53
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