Differential Diagnosis for Hepatitis B Serology

Given the serology results: HBcAb (Hepatitis B core antibody) positive, HBsAb (Hepatitis B surface antibody) reactive, and HBsAg (Hepatitis B surface antigen) negative, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Resolved Hepatitis B Infection: This is the most likely diagnosis because the presence of HBcAb indicates a past or current infection, HBsAb suggests immunity either from vaccination or past infection, and the absence of HBsAg indicates that the virus is not currently active. The combination of these markers is typical of individuals who have cleared the virus and are no longer infectious.

• Other Likely Diagnoses

  • Vaccinated Against Hepatitis B: Although less likely given the HBcAb positivity, it's possible in cases where the vaccine induced an immune response that included core antibody production, though this is not the standard interpretation.
  • Chronic Hepatitis B Infection in the Inactive Carrier State: In some cases, individuals with chronic hepatitis B may test negative for HBsAg due to mutations in the virus or immune suppression, but this would typically be accompanied by other markers such as HBeAg or HBV DNA levels.

• Do Not Miss Diagnoses

  • Hepatitis B Virus Mutation: Certain mutations in the HBV genome can lead to false-negative HBsAg results. It's crucial to consider this possibility, especially in immunocompromised patients or those with atypical serology patterns.
  • Window Period Infection: Although the HBsAb is reactive, suggesting immunity, there's a small chance this could represent a very early infection where the HBsAg has not yet appeared or has been cleared, but the core antibody has started to rise.

• Rare Diagnoses

  • HBsAg Negative, HBV DNA Positive ("Serologically Silent") Infection: This rare condition occurs when HBV DNA is detectable in the blood, but HBsAg is not, often due to immune suppression or specific viral mutations.
  • False-Positive or False-Negative Serology Results: Although rare, laboratory errors can occur, leading to incorrect interpretations of hepatitis B status. This should be considered, especially if clinical presentation and serology results do not align.