What lab work is ordered for a patient with a history of alcohol use?

Laboratory Work for Patients with a History of Alcohol Use

For patients with a history of alcohol use, a comprehensive laboratory panel should include liver function tests (AST, ALT with AST/ALT ratio calculation), GGT, alkaline phosphatase, bilirubin, albumin, prothrombin time/INR, complete blood count, and specific alcohol biomarkers. 1

Initial Laboratory Evaluation

Core Laboratory Tests

• Liver Function Tests:

  • AST (Aspartate Aminotransferase) - typically elevated 2-6 times upper limit of normal in alcoholic hepatitis 1
  • ALT (Alanine Aminotransferase) - usually lower than AST in alcoholic liver disease 1
  • AST/ALT ratio - highly suggestive of alcoholic liver disease when >2, and even more specific when >3 1, 2
  • GGT (Gamma-Glutamyl Transferase) - sensitive but less specific marker for alcohol use 1, 3
  • Alkaline phosphatase - may indicate cholestatic pattern of injury 1
  • Bilirubin (total and direct) - elevated in more severe liver disease 1
  • Albumin - decreased in chronic liver disease, indicating impaired synthetic function 2
  • Prothrombin time/INR - prolonged in advanced liver disease 2, 1

• Complete Blood Count:

  • Hemoglobin and hematocrit - may reveal anemia 4
  • Mean Corpuscular Volume (MCV) - macrocytosis is common in chronic alcohol use 3, 5
  • Platelet count - thrombocytopenia may indicate portal hypertension 4

Additional Biomarkers

• Carbohydrate-Deficient Transferrin (CDT) - provides the highest diagnostic performance (AUC 0.77) for detecting excessive drinking 3
• Phosphatidylethanol (PEth) - newer biomarker with good sensitivity and specificity 2

Tests to Exclude Other Causes of Liver Disease

• Hepatitis B and C serology
• Autoimmune markers (ANA, ASMA, AMA)
• Iron studies (ferritin, transferrin saturation)
• Alpha-1 antitrypsin
• Ceruloplasmin 1

Interpretation of Results

Patterns Suggestive of Alcoholic Liver Disease

• AST/ALT ratio >2 (highly specific for alcoholic etiology when >3) 1
• Elevated GGT with normal alkaline phosphatase 1, 3
• Macrocytosis (elevated MCV) 3, 5
• Elevated CDT (>2.6%) 3

Monitoring During Abstinence

Laboratory markers show different rates of normalization during abstinence:

• MCV: ~2.7% reduction after 12 weeks
• GGT: ~19% reduction after 12 weeks
• CDT: ~43% reduction after 12 weeks 3

Common Pitfalls and Caveats

1. No single test is diagnostic - Laboratory tests should be interpreted in conjunction with clinical history and physical examination 2

2. False positives are common - GGT can be elevated in non-alcoholic fatty liver disease, medication use, and advanced fibrosis of any cause 1

3. AST/ALT ratio >2 is more common in alcoholic cirrhosis - Only 2% of excessive drinkers without cirrhosis have AST/ALT >2, while 51% of those with alcoholic cirrhosis show this pattern 3

4. Positive predictive value varies with prevalence - For GGT, the positive predictive value is only about 25% in populations with 10% prevalence of problem drinking, but increases to about 55% in populations with 30% prevalence 6

5. Denial and underreporting are common - Laboratory tests can help identify alcohol use when history is unreliable 2

By systematically ordering and interpreting these laboratory tests, clinicians can better identify patients with alcohol-related liver disease, assess disease severity, and monitor response to abstinence.