What laboratory tests should be ordered for diagnosing hepatitis B (HBV)?

Laboratory Testing for Hepatitis B Diagnosis

For initial hepatitis B screening, order HBsAg (hepatitis B surface antigen) as the primary test, and if positive, complete the serologic panel with anti-HBc (total and IgM), anti-HBs, HBeAg, anti-HBe, and quantitative HBV DNA to determine infection status, disease phase, and treatment eligibility. 1, 2

Initial Screening Test

• HBsAg is the single most important initial test for detecting active HBV infection, appearing 30 days (range 6-60 days) after exposure and persisting in chronic infection 1
• A positive HBsAg result indicates active infection (either acute or chronic) and confirms the patient is infectious 1
• HBsAg positivity for >6 months defines chronic HBV infection 1, 2

Complete Serologic Panel (Once HBsAg is Positive)

Core Antibody Testing

• Anti-HBc (total) appears at symptom onset and persists for life, confirming current or previous HBV exposure 1, 2
• IgM anti-HBc distinguishes acute from chronic infection: positive in acute infection (persists up to 6 months), negative in chronic infection 1, 2
• Critical pitfall: IgM anti-HBc testing should only be ordered in patients with clinical evidence of acute hepatitis, as it has low positive predictive value in asymptomatic persons 1

Surface Antibody Testing

• Anti-HBs indicates recovery from infection or successful vaccination 1, 2
• In recovered patients, anti-HBs appears after HBsAg clearance 1

e Antigen System

• HBeAg indicates high viral replication (typically HBV DNA 10⁶-10¹⁰ IU/mL) 1, 2
• Anti-HBe indicates lower viral replication (typically HBV DNA 0-10⁵ IU/mL) after HBeAg clearance 1, 2

Essential Virologic Testing

• Quantitative HBV DNA is mandatory for all HBsAg-positive patients to assess viral replication, determine disease activity, and guide treatment decisions 1, 2
• Real-time PCR assays provide high sensitivity with a broad linear range (10-10⁸ IU/mL) 1
• Treatment thresholds: HBeAg-positive chronic hepatitis typically has HBV DNA ≥20,000 IU/mL; HBeAg-negative chronic hepatitis typically has HBV DNA ≥2,000 IU/mL 2
• Inactive carrier state is defined by HBV DNA <2,000 IU/mL with normal ALT 1, 2

Liver Function and Biochemical Tests

• ALT/AST assess liver inflammation and are elevated in active disease 1, 2
• Albumin and prothrombin time/INR evaluate synthetic liver function 2
• Bilirubin evaluates overall liver function 2
• Alkaline phosphatase and GGT provide additional markers of liver injury 2

Mandatory Coinfection Screening

• Anti-HCV testing is required to rule out hepatitis C coinfection, which significantly worsens prognosis 1, 2, 3
• Anti-HIV testing is essential in high-risk groups, as coinfection accelerates liver disease progression 1, 2, 3
• Anti-HDV testing is required in patients with injection drug use history or from endemic areas (HDV only infects in presence of HBV) 2, 3
• Anti-HAV IgG determines immunity status; vaccination is recommended if negative, as acute HAV coinfection increases risk of fulminant hepatic failure in CHB patients 1, 2

Additional Baseline Assessments

• Alpha-fetoprotein (AFP) for baseline HCC screening in all HBsAg-positive persons ≥20 years old 1, 2
• Baseline ultrasound for HCC surveillance when patient is first encountered, as delayed HCC diagnosis limits therapeutic options 1, 2
• Liver biopsy or transient elastography to assess fibrosis in patients with intermittent or persistent ALT elevations (not mandatory but recommended) 1, 2

Common Serologic Patterns and Interpretation

• Acute HBV: HBsAg positive, IgM anti-HBc positive 2
• Chronic HBV: HBsAg positive >6 months, total anti-HBc positive, IgM anti-HBc negative 2
• Resolved infection with immunity: HBsAg negative, anti-HBs positive, total anti-HBc positive 2
• Vaccine-induced immunity: HBsAg negative, anti-HBs positive, total anti-HBc negative 2
• Window period: Both HBsAg and anti-HBs negative, but IgM anti-HBc positive (occurs between HBsAg clearance and anti-HBs appearance) 2

Critical Pitfalls to Avoid

• Isolated anti-HBc positivity requires follow-up testing with HBsAg and HBV DNA, as it may represent resolved infection with waned anti-HBs, occult infection, or false-positive result 1, 2
• HBeAg-negative chronic hepatitis B can have lower HBV DNA levels (≥2,000 IU/mL) but still causes progressive liver disease with high risk of cirrhosis and HCC 1, 2
• Transient HBsAg positivity can occur up to 18 days after hepatitis B vaccination and is clinically insignificant 1
• Use the same HBV DNA assay for serial monitoring to ensure consistency 1

Monitoring Schedule for Confirmed Chronic HBV

• Untreated patients: ALT every 3-6 months, HBV DNA every 6-12 months, HBeAg/anti-HBe annually 2, 3
• Cirrhotic patients: More frequent monitoring with ultrasound and AFP every 6 months for HCC surveillance 2, 3
• Patients on treatment: Regular monitoring of ALT, HBV DNA, and other markers to assess treatment response 2