Hepatitis A Virus (HAV)
🔸Causes: Hepatitis A
🔸Transmission: Through ingestion of food or water contaminated with feces from an infected person (fecal-oral route)
Disease Characteristics
🔸Acute phase: Most cases resolve spontaneously
🔸Does not become chronic
🔸Prevention: Vaccination provides effective immunity and is widely used
Laboratory Testing
1.Serological Tests
🔸Anti-HAV IgM: Detects acute infection. Appears 1–2 weeks before symptom onset and persists for about 3–6 months.
👉A Positive result indicates an ongoing acute HAV infection.
🔸Anti-HAV IgG: Indicates immunity to HAV. Appears after infection or vaccination and persists lifelong.
👉A Positive result indicates previous infection or successful vaccination and provides long-term immunity.
Summary:
🔸Anti HAV IgM → Recent infection
🔸Anti HAV IgG → Long-term immunity
2. Molecular Tests
🔸HAV RNA detection (RT-PCR): Detects viral genetic material in blood or stool.
🔸Used to confirm acute infection, especially when IgM is not yet detectable.
🔸Commonly used in reference or research laboratories.
3. Biochemical Tests
🔸Assess liver function in conjunction with HAV diagnosis.
🔸Commonly altered parameters:
🔸ALT (Alanine aminotransferase): Markedly elevated
🔸AST (Aspartate aminotransferase): Elevated
🔸Total Bilirubin / Direct Bilirubin: Elevated → causes jaundice (yellow skin/eyes)
Note:
🔸ALT is usually higher than AST in acute hepatitis.
Diagnostic Approach for HAV
🔸Suspected acute HAV infection → test Anti-HAV IgM
🔸Assess Immunity → test Anti-HAV IgG
🔸Confirm Acute Infection (if IgM is unclear) → RT-PCR
🔸Evaluate liver injury → test ALT, AST, Bilirubin
Comments
Post a Comment