What diagnostic tests should be ordered when suspecting hepatitis?

Diagnostic Tests for Suspected Hepatitis

When suspecting hepatitis, a comprehensive panel of serological tests including HBsAg, anti-HBc (total and IgM), anti-HBs, HBeAg, anti-HBe, anti-HCV, and HCV RNA, along with liver function tests, should be ordered to establish the diagnosis, determine the type of viral hepatitis, and assess disease activity.

Initial Laboratory Evaluation

Serological Tests for Viral Markers

• Hepatitis B testing:

  • HBsAg (hepatitis B surface antigen) - primary marker for acute and chronic infection 1
  • Anti-HBc IgM - indicates acute HBV infection 1
  • Anti-HBc total - indicates past or current infection 1
  • HBeAg and anti-HBe - essential for determining phase of infection and viral replication 1
  • HBV DNA - confirms active viral replication and quantifies viral load 1

• Hepatitis C testing:

  • Anti-HCV antibody - initial screening test 1
  • HCV RNA (qualitative PCR) - confirms current infection 1
  • HCV RNA quantitative and genotype - if treatment is considered 1

• Other viral hepatitis markers:

  • Anti-HAV IgM - for acute hepatitis A 2
  • Anti-HDV - for hepatitis D (in HBsAg-positive patients) 1
  • Anti-HEV IgM and HEV RNA - for hepatitis E 1

Liver Function Tests

• Aminotransferases:

  • ALT (alanine aminotransferase) - primary marker of hepatocellular injury 3
  • AST (aspartate aminotransferase) - often elevated with ALT 3

• Cholestatic parameters:

  • Alkaline phosphatase
  • Gamma-glutamyl transpeptidase (GGT)
  • Bilirubin (total and direct)

• Synthetic function:

  • Albumin
  • Prothrombin time/INR
  • Complete blood count

Diagnostic Algorithm

1. Initial screening:

   • ALT, AST, alkaline phosphatase, bilirubin, albumin, and prothrombin time 1
   • HBsAg, anti-HBc (total and IgM), anti-HBs 1, 4
   • Anti-HCV antibody 1

2. If HBsAg positive:

   • Confirm with HBeAg, anti-HBe, and HBV DNA quantification 1
   • Test for anti-HDV in high-risk individuals 1
   • Determine if acute (anti-HBc IgM positive) or chronic (HBsAg persisting >6 months) 1, 4

3. If anti-HCV positive:

   • Confirm with HCV RNA (qualitative PCR) 1
   • If HCV RNA positive, obtain HCV genotype and viral load for treatment decisions 1

4. If both HBsAg and anti-HCV negative but hepatitis still suspected:

   • Test for anti-HAV IgM 2
   • Consider anti-HEV IgM and HEV RNA 1
   • Consider testing for autoimmune hepatitis markers (ANA, ASMA, anti-LKM-1) 1
   • Consider CMV, EBV, HSV testing in immunocompromised patients 1

Special Considerations

• Immunocompromised patients: Direct viral detection with PCR is essential as antibody tests may be negative 1

• Window period: In acute hepatitis B, there may be a period when HBsAg has disappeared but anti-HBs has not yet appeared; anti-HBc IgM will be positive during this time 1

• Isolated anti-HBc positive: May indicate resolved infection with undetectable anti-HBs, occult HBV infection, or false positive result; consider HBV DNA testing 1

• Normal liver enzymes: Do not exclude viral hepatitis; up to 50% of chronic HCV patients and many chronic HBV patients may have normal ALT levels 1, 5

Follow-up Testing

• For confirmed hepatitis B or C, additional evaluation should include:

  • Abdominal ultrasound to assess liver morphology 1
  • Consider liver biopsy or non-invasive fibrosis assessment (transient elastography) 1
  • Screen for co-infections (HBV/HCV, HIV) 1
  • Test for immunity to hepatitis A in patients with chronic hepatitis B or C 1

• Monitor liver function tests and viral markers periodically to assess disease activity and progression 1

Common Pitfalls to Avoid

• Relying solely on ALT/AST levels for diagnosis - normal values do not exclude viral hepatitis 1, 5
• Failing to test for all relevant viral markers - multiple hepatitis viruses can co-infect 1
• Not confirming anti-HCV positivity with HCV RNA - antibodies persist after viral clearance 1
• Missing acute HCV infection - anti-HCV may be negative while HCV RNA is positive 1
• Overlooking non-viral causes of hepatitis (autoimmune, drug-induced, alcoholic) 1, 6