American Board of Surgery Qualifying Exam (ABS QE) Practice Test

In the context of immunity, the presence of HBsAg and absence of HBsAb and HBcAb indicates what?

1. Previous infection

2. Current infection

3. Successful vaccination

4. Natural immunity

The correct answer is: Current infection

The presence of HBsAg (Hepatitis B surface antigen) alongside the absence of HBsAb (Hepatitis B surface antibody) and HBcAb (Hepatitis B core antibody) indicates a current infection with the Hepatitis B virus. HBsAg is a marker that signifies active viral replication and infection, showing that the virus is currently present in the bloodstream. The absence of HBsAb suggests that the body has not yet mounted an immune response, which would usually develop later in the course of the infection or after vaccination. Additionally, the absence of HBcAb indicates that there has not been a prior exposure to the virus or that the exposure is acute, further supporting the diagnosis of an active infection rather than a resolved one or an immune response due to vaccination. Thus, the combination of these serologic markers unmistakably points to a current Hepatitis B virus infection.