ROSH Gastrointestinal Practice Exam

What condition is indicated by the lab results showing HBsAg positive, HBsAb negative, and anti-HBc IgM positive?

1. Active infection with hepatitis B

2. Previous exposure to hepatitis A

3. Previous infection with both hepatitis B and C

4. Vaccination against hepatitis B

The correct answer is: Active infection with hepatitis B

The lab results showing HBsAg positive, HBsAb negative, and anti-HBc IgM positive indicate an active infection with hepatitis B. HBsAg (Hepatitis B surface antigen) is a marker that signifies the presence of the virus in the blood, indicating that a person is currently infected. When HBsAg is positive, it means the virus is actively replicating in the body. The absence of HBsAb (Hepatitis B surface antibody) suggests that the person has not recovered from the infection or has not been vaccinated. If the individual had previously been vaccinated or had resolved the infection, HBsAb would be positive. Anti-HBc IgM (IgM antibody to hepatitis B core antigen) being positive indicates a recent infection. This is particularly important because it distinguishes between a chronic infection and an acute phase of a hepatitis B infection. IgM antibodies usually appear shortly after infection and signal that the infection is recent. Taken together, these results clearly denote that the individual is experiencing an active Hepatitis B infection, distinguished by the presence of HBsAg and anti-HBc IgM, along with the absence of HBsAb.