From the Guidelines
Hepatitis serology for USMLE Step 1 is crucial for understanding the different phases of hepatitis infections and their corresponding viral markers. To approach hepatitis serology, it's essential to understand the different viral markers and their implications in various hepatitis infections.
Key Markers for Hepatitis Infections
- For Hepatitis A, anti-HAV IgM indicates acute infection, while anti-HAV IgG shows past infection or immunity.
- In Hepatitis B,
- HBsAg is the surface antigen indicating active infection;
- anti-HBs shows immunity from vaccination or resolved infection;
- HBeAg suggests high viral replication and infectivity;
- anti-HBe appears during recovery;
- anti-HBc IgM indicates acute infection; and
- anti-HBc IgG shows past or chronic infection, as noted in 1.
- For Hepatitis C, anti-HCV antibodies indicate exposure, while HCV RNA confirms active infection.
- Hepatitis D requires HBsAg for replication, so HDV antibodies are only meaningful in HBsAg-positive patients.
- For Hepatitis E, anti-HEV IgM indicates acute infection, while IgG shows past infection. It's also critical to remember the "window period" in Hepatitis B when HBsAg disappears but anti-HBs hasn't yet appeared, during which anti-HBc IgM is the only marker present, as discussed in 1. Additionally, HBeAg positivity correlates with higher infectivity and worse prognosis in chronic HBV, highlighting the importance of serologic testing in managing and preventing hepatitis infections, as emphasized in 1. These serological patterns are high-yield for distinguishing between acute, chronic, and resolved infections on USMLE Step 1 questions, and understanding them is vital for effective patient care and prevention strategies, as outlined in 1.
From the Research
Hepatitis Serology Overview
- Hepatitis B serology involves various markers, including HBsAg, HBsAb, HBeAg, HBeAb, and HBcAb, which can be used to diagnose and monitor the disease 2.
- The presence of all 5 positive serum markers, including HBsAg, HBsAb, HBeAg, HBeAb, and HBcAb, is a rare pattern that may occur in patients with chronic hepatitis B 2.
Predicting Liver Fibrosis
- Quantitative HBcrAg and HBcAb can be used to predict liver fibrosis levels in chronic hepatitis B patients, with HBcrAg having good performance in HBeAg-negative patients 3.
- HBsAg has good performance in predicting liver fibrosis levels in both HBeAg-positive and HBeAg-negative patients 3.
HBV Reactivation and HBsAb
- The presence of HBsAb can protect against clinical HBV reactivation related to direct-acting antiviral therapy for hepatitis C 4.
- HBsAb titres greater than 30 iU/L may be required for the most pronounced prevention of reactivation 4.
Predicting HBsAg or HBeAg Seroconversion
- The presence of baseline HBsAb-specific B cells can predict HBsAg or HBeAg seroconversion in patients with chronic hepatitis B on treatment 5.
- Patients with baseline HBsAb-specific B cells and HBsAg ≤ 1500 have a higher chance of HBsAg clearance at the end of treatment 5.
Screening Tests for Hepatitis B
- Automated chemiluminescent immunoassays (CLIAs) can be used for the detection of HBV, HCV, and HIV in blood donor screening, with high concordance and specificity between different systems 6.