Laboratory Markers for Alcohol Use

PATHCHAT Edition No. 24
Please contact your local Ampath pathologist for more information.

Author: Dr. René van der Watt, Ampath National Reference Laboratory, Department of Esoteric Sciences, Centurion

Definitions & Key Terms

🔹 Alcohol Use Disorder (AUD)

• Reclassified by DSM-5 (2013), replacing the older DSM-IV classification.
• Defined by 11 criteria grouped into four categories:
  1. Impaired control (e.g., drinking more than intended, failed attempts to cut down).
  2. Social impairment (e.g., failure to meet work/home obligations due to drinking).
  3. Risky use (e.g., continued use despite health problems).
  4. Pharmacological effects (e.g., tolerance, withdrawal).

✅ Severity is classified as:

• Mild: 2–3 criteria met.
• Moderate: 4–5 criteria met.
• Severe: 6+ criteria met.

✅ Remission Categories:

• Early remission: 3–11 months without symptoms (except cravings).
• Full remission: More than 12 months without symptoms.

🔹 Additional Key Terms:

• Alcoholism: Chronic alcohol dependence with cravings, tolerance, and withdrawal.
• Withdrawal: Physical symptoms from reduced alcohol levels after prolonged use.
• Tolerance: Higher alcohol doses required to achieve the same effect.
• Heavy Episodic Drinking: ≥60 g of alcohol in one session at least once per month.

WHO Guidelines for Alcohol Consumption Risk Levels

🔹 For Males:

• High-risk drinking: More than 60 g/day (5+ beers/day).
• Medium-risk drinking: 41–60 g/day (3–4 beers/day).
• Low-risk drinking: 1–40 g/day (1–2 beers/day).

🔹 For Females:

• High-risk drinking: More than 40 g/day (3+ beers/day).
• Medium-risk drinking: 21–40 g/day (2 beers/day).
• Low-risk drinking: 1–20 g/day (1 beer/day).

✅ One standard drink contains approximately 13 g of ethanol, found in:

• One beer (330 ml, 5% alcohol).
• One glass of wine (140 ml, 12% alcohol).
• One shot of spirits (40 ml, 40% alcohol).

Alcohol Use in South Africa (WHO Report, 2010)

🔹 Prevalence of Alcohol Use Disorders:

• Males: 10%
• Females: 1.5%
• Both genders combined: 6%

🔹 Prevalence of Heavy Episodic Drinking:

• Males: 18%
• Females: 4%
• Both genders combined: 10%

Screening for Alcohol Use Disorders

🔹 Screening Methods:
✅ WHO-developed AUDIT Questionnaire (10-item test)

• Sensitivity: 51% – 97%.
• Specificity: 78% – 96%.

✅ Limitations of Questionnaires:

• Patients may underreport alcohol use.
• Not reliable in individuals with altered mental status.

Laboratory Markers for Alcohol Use

✅ Classification of Laboratory Markers:

1. State markers: Reflect recent drinking patterns.
2. Trait markers: Identify individuals genetically predisposed to alcohol use disorders (research-based, not widely available).

✅ Types of Markers:

• Direct markers: Measure alcohol or its metabolites.
• Indirect markers: Reflect alcohol's effects on the body (e.g., liver damage).

🔹 Current Laboratory Markers Are Used To:

• Enhance clinical suspicion of alcohol use disorders.
• Provide objective data on alcohol consumption.
• Detect heavy drinking.
• Monitor relapse in alcohol-dependent individuals.

📌 No single marker is sufficient; combining multiple tests improves accuracy.

Commonly Used Laboratory Markers

1. Blood Ethanol Level (Direct Marker)

✅ Used to detect acute alcohol consumption.
✅ Legal limit in South Africa: 0.05 g/dL (for driving).
✅ Limitations:

• Short detection window (hours).
• Does not detect chronic alcohol use.

2. Gamma-Glutamyl Transferase (GGT) (Indirect Marker)

✅ Most commonly used marker for chronic alcohol use.
✅ Elevated in heavy drinkers (>70 g/day for men, >40 g/day for women).
✅ Takes 2–5 weeks to normalize after abstinence.
✅ Limitations:

• Also elevated in liver disease, diabetes, obesity, smoking, and medications.

3. Carbohydrate-Deficient Transferrin (CDT) (Indirect Marker)

✅ Highly specific for chronic alcohol use (>50–80 g/day for at least a week).
✅ Takes 2–4 weeks to normalize after abstinence.
✅ Best for detecting relapse.
✅ Limitations:

• Less sensitive in females.
• False positives in non-alcoholic liver disease.

4. GGT-CDT Combined Test

✅ Combining GGT and CDT improves accuracy.
✅ Detects chronic alcohol use with high sensitivity and specificity.
✅ Unaffected by liver disease in heavy drinkers.

5. Mean Corpuscular Volume (MCV) (Indirect Marker)

✅ Reflects increased red blood cell size due to chronic alcohol use.
✅ Useful for long-term alcohol use monitoring.
✅ Takes 2–4 months to normalize.
✅ Limitations:

• Not useful for detecting recent alcohol use.
• Elevated in vitamin B12 deficiency, hypothyroidism, and some medications.

6. Aspartate Aminotransferase (AST) / Alanine Aminotransferase (ALT) Ratio (Indirect Marker)

✅ AST/ALT ratio >2 suggests alcoholic liver disease.
✅ Indicates advanced liver damage rather than alcohol consumption itself.
✅ Limitations:

• Elevated in non-alcoholic liver disease and other conditions.

Key Takeaways for Clinicians

✅ No single test is sufficient to diagnose alcohol use disorder.
✅ The most effective screening combines the AUDIT questionnaire, CDT, and GGT.
✅ CDT is the best biomarker for monitoring abstinence and detecting relapse.
✅ MCV is useful for detecting long-term alcohol use but not recent drinking.
✅ GGT is commonly used but lacks specificity.
✅ Blood ethanol is useful for detecting acute alcohol intake but has a short detection window.

References

1. Von Ghia L et al. (2014). Diagnostic challenges in alcohol-use disorder and alcoholic liver disease. World Journal of Gastroenterology, 20(25), 8024–8032.
2. Sharpe PC. (2001). Biochemical detection and monitoring of alcohol abuse and abstinence. Ann Clin Biochem, 38, 652–664.
3. Babor TF et al. (2001). AUDIT – 2nd edition. World Health Organization.
4. Tavakoli HR et al. (2011). Review of current clinical biomarkers for alcohol dependence. Innov Clin Neurosci, 8(3), 26–33.