Alcoholism Workup

Updated: Sep 12, 2017
  • Author: Warren Thompson, MD, FACP; Chief Editor: Randon S Welton, MD  more...
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Laboratory Studies


Alcohol biomarkers are physiological indicators of alcohol exposure or ingestion and may reflect the presence of an alcohol use disorder. These biomarkers are not meant to be a substitute for a comprehensive history and physical examination by an appropriate health professional. Instead, alcohol biomarkers should be a complement to self-reported measures of drinking. [4]

In a population of psychiatric patients, research evidence has shown the usefulness of biological measures in the detection of alcohol use disorders when compared with patient self-report. A 2007 study of 486 consecutively admitted psychiatric patients showed a low correlation between self-reported consumption of alcohol and illicit drugs and biological measures; 52% of the patients underreported their consumption of illicit drugs when compared with urine toxicology screening results; 56% of patients underreported alcohol use as evaluated by carbohydrate-deficient transferrin (CDT), and 37% of patients underreported alcohol use as evaluated by CDT + gamma glutamyltransferase (GGT). [40] Replication of such research in a primary care population is needed to show that biological measures aid the primary care clinician in detecting alcohol use disorders.

Alcohol biomarkers are generally divided into indirect and direct biomarkers. [4]

Indirect alcohol biomarkers suggest heavy alcohol use by detecting the toxic effects that alcohol may have had on organ systems or body chemistry. [4]

  • Indirect alcohol biomarkers include aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyltransferase (GGT), mean corpuscular volume (MCV), and carbohydrate-deficient transferrin (CDT). [4]
  • GGT, AST, and MCV are the most frequently used indirect biomarkers. [5] As a screen for alcohol dependence, the sensitivity/specificity of CDT is generally higher than AST, ALT, GGT, or MCV. [4, 41, 6] (See Table 2 below.) CDT is less sensitive/specific in women than men. [42]
  • CDT is a collection of various isoforms of the iron transport protein transferrin. [5] Alcohol consumption above 50-80 g/d for 2-3 weeks appears to increase serum concentrations of CDT. [6, 41] CDT tends to distinguish chronic heavy drinkers from light social drinkers. [5] A number of different ways are available to measure CDT; some may be better than others, depending on factors such as the type of alcohol consumption and gender. [43]
  • The combination of GGT and CDT compared with GGT or CDT alone shows a higher diagnostic sensitivity, a higher diagnostic specificity, and a stronger correlation with the actual amounts of alcohol consumption (see Table 2 below). [41, 6] Combination GGT/CDT values appear to increase after the daily alcohol consumption exceeds a threshold of 40 g. [6] This approach is cost-effective, easy to manage in hospital laboratories, and should be suitable for routine clinical care. [6]
  • Other indirect alcohol biomarkers of emerging interest include total serum sialic acid (TSA), 5-hydroxytryptophol (5-HTOL), N-acetyl-beta-hexosaminidase (Beta-Hex), plasma sialic acid index of apolipoprotein J (SIJ), and salsolinol. [7]

Direct alcohol biomarkers are analytes of alcohol metabolism. [4]

  • Direct alcohol biomarkers include alcohol itself and ethyl glucuronide (EtG). [4]
  • A blood alcohol level might be helpful in the office if the patient appears intoxicated but is denying alcohol abuse. A blood alcohol level in excess of 300 mg/dL, a blood alcohol level of greater than 150 mg/dL without gross evidence of intoxication, or a blood alcohol level of greater than 100 mg/dL upon routine examination indicates alcoholism with a high degree of reliability. The short half-life of alcohol limits its use widely as a biomarker. [6] As the blood alcohol level detects alcohol intake in the previous few hours, it is not necessarily a good indicator of chronic excessive drinking. [5]
  • EtG is a minor, nonoxidative, water-soluble, stable, and direct metabolite of alcohol that is formed by the conjugation of ethanol with activated glucoronic acid. [41, 6, 5] Shortly after alcohol intake, even in small amounts, EtG becomes positive. [5] After complete cessation of alcohol intake, EtG can be detected in urine for up to 5 days after heavy binge drinking [7, 6] , making EtG an important biomarker of recent alcohol consumption. [5] A 2006 report by the Substance Abuse and Mental Health Services Administration states that the use of EtG should be considered as a potential valuable clinical tool, but the use of EtG in forensic settings is premature. [4]
  • Other direct alcohol biomarkers of emerging interest include acetaldehyde, fatty acid ethyl esters (FAEE), Ethyl Sulfate (EtS), and Phosphatidylethanol (PEth). [4, 7]

Table 2. Sensitivity and Specificity of Alcohol Biomarkers* (Open Table in a new window)

Biomarker Sensitivity (%) Specificity (%)
AST 15-69 47-68
ALT 18-58 50-57
GGT 34-85 11-95
MCV 34-89 26-95
CDT 39-94 82-100
CDT + GGT 90 † 98
Alcohol 0-100 0-100
EtG 76-91 77-92
*Values vary considerably according to gender, age, drinking pattern, prevalence of alcohol abuse/dependence, and prevalence of comorbidity, among other factors. [41, 6, 42, 44, 45]

† The sensitivity comes from one study in Finland, which uses a special formula. This study needs to be replicated. [46]


Other Tests

The possibility of polysubstance abuse/dependence justifies performing a blood/urine toxicology screen for other substances of abuse.