Testing for Hepatitis Infection
All patients presenting with biochemical evidence of hepatitis should undergo simultaneous first-line testing for hepatitis A, B, C, and E at initial presentation, as hepatitis E is now recognized as the most common cause of acute viral hepatitis in many developed countries. 1
Initial Serologic Testing Panel
The comprehensive initial workup should include:
Hepatitis A Testing
- HAV IgM antibody to indicate acute infection 1
- This antibody appears during the acute phase and confirms active HAV infection 2
Hepatitis B Testing
- Hepatitis B surface antigen (HBsAg) - primary marker for active HBV infection, with positivity >6 months defining chronic infection 1, 3, 4
- Hepatitis B core antibody (anti-HBc) - required before initiating any HCV treatment to detect current or prior HBV infection 3, 4
- Anti-HBc IgM - specifically indicates acute HBV infection 1
- For chronic HBV evaluation: HBeAg status, HBV DNA levels, and liver function tests 5, 6
Hepatitis C Testing
The testing sequence follows a two-step algorithm 7:
Step 1: HCV Antibody Testing
- Use either rapid or laboratory-conducted assay for HCV antibody 7
- A reactive result indicates one of three possibilities: current infection, past resolved infection, or false positivity 7
Step 2: HCV RNA Testing (if antibody positive)
- HCV RNA by nucleic acid testing (NAT) to confirm active viremia 7, 1
- If HCV RNA is detected: current HCV infection 7
- If HCV RNA is not detected: past resolved infection or false antibody positivity 7
Critical timing considerations:
- HCV antibody may be negative during the first 6 weeks after exposure 7
- Up to 20% of acute hepatitis C cases will be anti-HCV negative at initial presentation due to delayed seroconversion 1
- Seroconversion may be delayed or absent in immunosuppressed individuals 7
Hepatitis E Testing
- HEV IgM antibody - appears 4-6 weeks after exposure and lasts 2-4 months 1, 8
- HEV RNA by NAT - essential for diagnosis in immunosuppressed patients where antibodies may be undetectable 1, 8
- HEV testing should not be delayed until HAV, HBV, and HCV are negative; test all simultaneously 1
Hepatitis D Testing (if HBV positive)
- Anti-HDV should be tested in HBsAg-positive or anti-HBc IgM-positive patients, particularly those with injection drug use history or from endemic areas 1
Supporting Laboratory Tests
Liver Function Assessment
- ALT and AST - assess liver inflammation; ALT >2.5 times upper limit of normal required for hepatitis C diagnosis 1
- Total bilirubin - evaluates liver function and severity in acute injury 1
- Albumin, INR, and CBC with platelet count - assess synthetic function and severity 7
Additional Fibrosis Assessment (for chronic hepatitis)
- APRI score (AST-to-platelet ratio index) 7
- FIB-4 score 7
- Transient elastography for liver stiffness measurement 7
Critical Pitfalls to Avoid
Timing and Window Period Issues
- Do not miss the serologic "window period" in hepatitis B when both HBsAg and anti-HBs are negative; anti-HBc IgM will be positive during this time 1
- For suspected acute HCV with negative antibody, test HCV RNA directly or repeat antibody testing at 6 weeks 7
- In immunosuppressed patients with unexplained liver disease, test HCV RNA even if anti-HCV is negative 7
Testing Sequence Errors
- Never delay HEV testing until other viral markers are negative - test all hepatitis viruses simultaneously 1, 8
- Test for HEV in suspected drug-induced liver injury (DILI), as 13% of presumed DILI cases are actually acute hepatitis E 1
Special Populations
- For acute HCV infection diagnosis, viral fluctuations >1 log10 IU/mL may indicate acute infection, and HCV RNA may be transiently negative 7
- In immunosuppressed patients with chronic HEV, NAT testing is essential as anti-HEV antibodies are often undetectable 8
Autoimmune Hepatitis Testing (if viral markers negative)
If all viral hepatitis markers are negative, test for:
- ANA, SMA, anti-LKM-1, and AMA to evaluate for autoimmune hepatitis 1