Laboratory Evaluation for Suspected Hepatitis
For patients with suspected hepatitis, a comprehensive laboratory workup should include serologic markers for viral hepatitis, liver function tests, and tests to assess liver disease severity and rule out coinfections.
Initial Laboratory Evaluation
Serologic Tests for Viral Hepatitis
Hepatitis B markers:
- HBsAg (hepatitis B surface antigen)
- Anti-HBs (hepatitis B surface antibody)
- Anti-HBc total and IgM (hepatitis B core antibody)
- HBeAg (hepatitis B e antigen) and anti-HBe (antibody to HBeAg)
- HBV DNA quantification 1
Tests for other viral hepatitis:
- Anti-HCV (hepatitis C virus antibody)
- Anti-HDV (hepatitis D virus antibody) - especially in persons from endemic areas or with history of injection drug use
- Anti-HIV in high-risk groups 1
- HAV IgM antibody (if acute hepatitis is suspected)
- HEV IgM antibody (if clinically indicated, especially in travelers from endemic areas) 1
Liver Function Tests
- Complete blood count with platelets
- Liver enzyme panel:
- AST (aspartate aminotransferase)
- ALT (alanine aminotransferase)
- Alkaline phosphatase
- Gamma-glutamyl transpeptidase (GGT)
- Bilirubin (total and direct)
- Albumin
- Prothrombin time/INR 1
Additional Tests
- Creatinine and blood urea nitrogen (to assess kidney function)
- Alpha-fetoprotein (AFP) - baseline screening for hepatocellular carcinoma in high-risk patients 1
Interpretation of Hepatitis B Serologic Markers
Acute Hepatitis B
- Positive HBsAg and IgM anti-HBc
- HBV DNA typically elevated
- Elevated liver enzymes (ALT/AST) 1
Chronic Hepatitis B
- HBsAg positive for >6 months
- HBeAg-positive chronic hepatitis B: HBV DNA ≥20,000 IU/mL
- HBeAg-negative chronic hepatitis B: HBV DNA ≥2,000 IU/mL
- Persistent or intermittent elevation of AST/ALT 1
Inactive HBV Carrier State
- HBsAg positive for >6 months
- HBeAg negative, anti-HBe positive
- HBV DNA <2,000 IU/mL
- Persistently normal ALT/AST levels 1
Resolved Hepatitis B
- HBsAg negative
- Anti-HBs and anti-HBc positive
- Undetectable HBV DNA 1
Special Considerations
HIV Coinfection
- Patients with HIV infection should be tested for both HBsAg and anti-HBc
- If either is positive, test for HBV DNA
- HIV coinfection can lead to higher HBV DNA levels and more severe liver disease 1
Occult Hepatitis B
- Consider in patients with isolated anti-HBc positivity
- May require HBV DNA testing to confirm 1
High-Risk Populations
- Individuals born in endemic areas (13% HBsAg prevalence)
- Men who have sex with men (6% HBsAg prevalence)
- Injection drug users (7% HBsAg prevalence)
- Dialysis patients (3-10% HBsAg prevalence)
- HIV-infected patients (8-11% HBsAg prevalence) 1
Follow-up Testing
For patients with abnormal initial results:
- If HBsAg positive: Repeat testing in 6 months to distinguish between acute and chronic infection
- If liver enzymes remain elevated: Consider liver biopsy to assess disease severity
- For chronic HBV: Regular monitoring of HBV DNA, liver enzymes, and AFP 1
Pitfalls to Avoid
- Don't rely solely on ALT/AST levels - they may be normal in some patients with chronic hepatitis B, especially in the immune tolerant phase 1
- Don't miss testing for HDV in HBsAg-positive patients - HDV coinfection leads to more severe disease 1
- Don't overlook isolated anti-HBc - may indicate occult HBV infection requiring HBV DNA testing 1
- Don't forget to screen for hepatocellular carcinoma in high-risk patients with chronic hepatitis B 1
By following this comprehensive laboratory evaluation approach, clinicians can accurately diagnose hepatitis, determine its etiology, assess disease severity, and guide appropriate management decisions.