Acute hepatitis B infection is best indicated by which serologic combination?

• A. HBsAg positive with IgM anti-HBc positive
• B. HBsAg negative with anti-HBs positive
• C. HBsAg positive with anti-HBc IgG positive
• D. All of the above

Answer: (A)

Acute hepatitis B infection is best indicated by HBsAg positive together with IgM anti-HBc positive. HBsAg shows that the virus is currently present in the blood, signaling infection. The IgM class of antibodies to the core antigen (anti-HBc) appears early during an acute infection and is a hallmark of recent or active HBV replication. This IgM response distinguishes acute infection from later stages.

If HBsAg is negative with anti-HBs positive, that pattern reflects immunity from recovery or vaccination, not an acute infection. If HBsAg is positive with anti-HBc IgG positive, that points to a longer-standing infection—likely chronic or past infection with persistent antigen—rather than an acute process.