How to Order Hepatitis B and C Labs
For hepatitis B screening, order HBsAg (hepatitis B surface antigen) as the primary test, and for hepatitis C screening, order anti-HCV antibody with reflex to HCV RNA testing to confirm active infection. 1, 2
Hepatitis B Testing Algorithm
Initial Screening Panel
- HBsAg (Hepatitis B surface antigen): Primary screening test to detect current acute or chronic HBV infection 1, 2
- Total anti-HBc (Hepatitis B core antibody): Detects both recent and past infections; order total (not IgM) anti-HBc 1, 2
- Anti-HBs (Hepatitis B surface antibody): Determines immunity status from vaccination or past infection 1, 2
Interpretation and Follow-Up Testing
If HBsAg is positive: This indicates current infection (acute or chronic). Immediately order: 2
- HBeAg and anti-HBe: To determine viral replication status (HBeAg positive = high replication; anti-HBe positive = low replication) 2
- HBV DNA quantification: Essential for assessing viral load (HBeAg-positive chronic hepatitis B: ≥20,000 IU/mL; HBeAg-negative: ≥2,000 IU/mL) 2
- IgM anti-HBc: To distinguish acute infection (IgM positive) from chronic infection (IgM negative) 1, 2
If isolated anti-HBc positive (HBsAg negative, anti-HBs negative): Order HBV DNA testing to rule out occult hepatitis B infection 1, 2
Additional Baseline Assessment for Confirmed HBV
- Liver function tests: AST/ALT, alkaline phosphatase, gamma-glutamyl transpeptidase, bilirubin, albumin, prothrombin time 2
- Complete blood count with platelets 2
- Coinfection screening: Anti-HCV, anti-HDV (if history of drug abuse), anti-HIV (if high-risk) 2
- Alpha-fetoprotein and liver ultrasound: For hepatocellular carcinoma screening 2
Hepatitis C Testing Algorithm
Initial Screening
- Anti-HCV antibody test: Primary screening test using FDA-approved laboratory-based or point-of-care assay 2
- Reflex to HCV RNA (NAT): If anti-HCV is positive, automatically reflex to HCV RNA nucleic acid testing without requiring a second blood draw 2
Interpretation
- Anti-HCV positive + HCV RNA positive: Current active HCV infection requiring treatment 2
- Anti-HCV positive + HCV RNA negative: Past resolved infection or false positive; patient should be informed they do not have active infection but are not protected from reinfection 2
- Anti-HCV negative: No HCV infection detected 2
Pre-Treatment Testing (If HCV RNA Positive)
- Quantitative HCV RNA: Document baseline viral load prior to initiating antiviral therapy 2
- HCV genotype testing: May be considered if it alters treatment recommendations 2
- Liver function tests: To assess severity of liver disease 1, 3
Special Circumstances
Recent Exposure (Within 6 Months)
- For HBV: Order HBV DNA directly, as HBsAg may not yet be detectable 1
- For HCV: Order HCV RNA directly or repeat anti-HCV testing at 6 months post-exposure, as antibodies may not have developed 2, 1
Immunocompromised Patients
Patients at Risk for Reinfection
- After previous spontaneous or treatment-related viral clearance, order HCV RNA testing directly (anti-HCV will remain positive) 2
HBV/HCV Coinfection Screening
- All HCV patients must be tested for HBV before initiating HCV treatment by measuring HBsAg and anti-HBc, as HBV reactivation can cause fulminant hepatitis, hepatic failure, and death 4, 1
Critical Pitfalls to Avoid
- Do not rely solely on HBsAg for HBV screening—it will miss occult infections, especially in immunocompromised patients; always include anti-HBc 1
- Do not order anti-HCV alone without confirmatory HCV RNA testing—this cannot distinguish current infection from resolved past infection 1, 2
- Do not ignore isolated anti-HBc positivity—this requires HBV DNA testing to rule out occult infection 1, 2
- Do not skip HBV testing before HCV treatment—failure to detect HBV coinfection can result in fatal HBV reactivation during HCV therapy 4
- Do not order IgM anti-HBc as initial screening—order total anti-HBc first; IgM is only for distinguishing acute from chronic infection after HBsAg positivity is confirmed 1, 2