Interpretation of hepatitis B serologic markers
A positive
HBsAg indicates the presence of hepatitis B surface antigen, which means the person currently harbors the virus. In contrast,
anti-HBs is the protective antibody; its presence signals immunity, whether from resolved infection or from vaccination. The
anti-HBc (core antibody) is a marker of exposure to the actual virus, not of protection, and it appears only after natural infection, never after vaccination alone.
The four family members can be classified by combining these three markers.
The husband is negative for HBsAg, anti-HBs, and anti-HBc, which means he has never been exposed to hepatitis B and has no immunity. He is susceptible and is the correct candidate for vaccination.
| Family member | HBsAg | Anti-HBs | Anti-HBc | Interpretation | Action |
|---|
| Mother | Negative | Positive | Positive | Resolved past infection with natural immunity | No vaccine needed |
| Husband | Negative | Negative | Negative | Susceptible, never infected, not immune | Refer for hepatitis B vaccination |
| Sister | Positive | Negative | Positive | Current or chronic HBV infection | Medical evaluation, not vaccination |
| Brother | Negative | Positive | Negative | Immunity from prior vaccination | No vaccine needed |
Key point! The presence of
anti-HBc distinguishes immunity from natural infection from immunity from vaccination. The mother has both anti-HBs and anti-HBc, indicating she was infected in the past and cleared the virus. The brother has anti-HBs but no anti-HBc, which is the classic profile of vaccine-induced immunity. Neither requires vaccination.
Watch out! The sister has a positive HBsAg, which means she is currently infected. Vaccination is ineffective once infection is established; instead, she needs further evaluation for chronic hepatitis B, including liver function tests, hepatitis B e antigen (HBeAg) status, and HBV DNA levels to assess disease activity and infectivity.
For the index patient, the 29-year-old woman with positive HBsAg and normal ALT, the occupational health nurse should recognize that she may be a chronic carrier. Normal ALT and absence of symptoms do not rule out chronic infection. She should be counseled about transmission prevention, the importance of regular monitoring, and the need for family members to be screened and vaccinated if susceptible. The serologic screening of her family at the RHU is a key public health measure, because household contacts of a chronic carrier have a significant risk of acquiring HBV through percutaneous or mucosal exposure to infected blood or body fluids.
Interpreting hepatitis B serology requires looking at all three markers together, not any single result in isolation. A negative HBsAg alone does not confirm immunity, and a positive anti-HBc alone does not mean the person is protected. The husband’s triple-negative profile is the only one that indicates susceptibility and therefore the only one that warrants referral for vaccination.