Infection Control · patient case question
For Patient D — serology shows anti-HBs POSITIVE, anti-HBc NEGATIVE, HBsAg NEGATIVE. What does this indicate?
Patient case: Five patients, five medical problems
Patient: Five separate patients in one session
Chief Complaint: A: mid-appointment shakiness. B: routine care. C: reviewing a medication list. D: an occupational health question. E: a child brought in by a parent.
Background: A: type 1 diabetes, took her insulin but skipped breakfast. B: 40-pack-year smoker with a chronic productive cough. C: on long-term corticosteroid therapy. D: a dental assistant with a new serology report. E: 6-year-old with sore throat, fever and a rash.
Findings: A: shaky, sweating, confused but conscious and able to swallow; capillary glucose 54 mg/dL. B: barrel chest, prolonged expiration. E: a sandpaper-textured rash, and a tongue with a white coating through which swollen red papillae project.
Show answer and explanation
Correct answer: D. Immunity through vaccination
- A. Immunity from resolved natural infection shows anti-HBs POSITIVE and anti-HBc POSITIVE together, with HBsAg negative — because the person encountered the entire virus, including its core protein, rather than just the surface antigen.
- B. Acute infection is HBsAg positive with IgM anti-HBc positive, often during the window period when anti-HBs has not yet appeared.
- C. Chronic infection is defined by HBsAg positive for more than six months, with anti-HBc positive and anti-HBs negative. HBsAg is negative here.
- D. CORRECT. Anti-HBs is the antibody to the SURFACE ANTIGEN and it signifies IMMUNITY. The vaccine contains recombinant surface antigen ONLY, so a vaccinated person develops anti-HBs and nothing else. The NEGATIVE anti-HBc is the discriminator that settles it — core antibody is produced only in response to the whole virus and is never generated by the vaccine.
Note: The employer MUST make the hepatitis B vaccine series available at NO COST within 10 working days of assignment to a role with occupational exposure; offering it is mandatory for the employer, accepting it is voluntary for the employee. Post-vaccination testing is performed one to two months after the final dose, and an anti-HBs titre of 10 mIU/mL or above indicates protection. No booster is currently recommended for immunocompetent responders.
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