Hepatitis B serology

21 DOH Abu Dhabi (HAAD) lab licensing practice questions on Hepatitis B serology, part of Immunology and Serology. The first 21 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   A 63-year-old man with diffuse large B-cell lymphoma was screened before six cycles of rituximab-based chemotherapy: HBsAg nonreactive, total anti-HBc reactive, anti-HBs 24 mIU/mL and HBV DNA not detected. He declined antiviral prophylaxis and then missed his monitoring visits. Seven months after the last cycle he is jaundiced, with ALT 940 U/L (reference below 40) and bilirubin 86 µmol/L (5.0 mg/dL). Results: HBsAg reactive (confirmed by neutralization); IgM anti-HBc weakly reactive; anti-HBs below 2 mIU/mL; HBeAg reactive; HBV DNA 3.8 × 10^7 IU/mL. Markers of hepatitis A, C and E are negative, and he reports no new sexual or blood exposure. The most likely diagnosis is:

   1. AChronic hepatitis B missed at screening
   2. BA new acute hepatitis B infection
   3. CDrug-induced liver injury
   4. DReactivation of a resolved HBV infection

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   Answer: D · Reactivation of a resolved HBV infection

   Before treatment he had anti-HBc and anti-HBs without HBsAg, the profile of a resolved infection; HBV still persists in his liver as cccDNA, held in check by the immune system. Rituximab removes B cells, anti-HBs falls, and the virus can replicate again, so HBsAg reappears ('reverse seroconversion') with a high viral load and a hepatitis flare. IgM anti-HBc can return at a low level during reactivation, so it does not prove a new infection, and he had no new exposure. Drug injury would not produce HBsAg and 10^7 IU/mL of HBV DNA, and chronic infection was excluded at screening by a nonreactive HBsAg and undetectable DNA. Guidelines advise antiviral prophylaxis for anti-HBc-positive patients who receive rituximab, continued for many months after the last dose.

   • A: HBsAg was nonreactive and HBV DNA undetectable before treatment.
   • B: IgM anti-HBc can reappear in reactivation; his pre-treatment anti-HBc shows earlier infection.
   • C: Drug injury does not make HBsAg appear or produce a high HBV DNA.

2. Question 2 · Hard

   A 31-year-old nurse, born in a country where hepatitis B is common, has pre-employment screening at a hospital in Abu Dhabi. She has no record of hepatitis B vaccination. Results: HBsAg nonreactive; total anti-HBc reactive (S/CO 6.8, repeatedly reactive); IgM anti-HBc nonreactive; anti-HBs below 2 mIU/mL; HBV DNA not detected; ALT 21 U/L (reference below 40). She receives one dose of hepatitis B vaccine, and 3 weeks later her anti-HBs is 640 mIU/mL. What is the best interpretation?

   1. AWindow period of an acute hepatitis B infection
   2. BOccult hepatitis B infection needing antiviral treatment
   3. CFalse-positive anti-HBc, with a primary vaccine response
   4. DPast infection, with an anamnestic anti-HBs response

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   Answer: D · Past infection, with an anamnestic anti-HBs response

   Isolated anti-HBc has three main explanations: a past infection whose anti-HBs has fallen below detection, a false-positive anti-HBc, or occult infection; the negative IgM anti-HBc excludes the core window of acute infection. HBV DNA is not detected, which makes occult infection unlikely, and the high, repeatable S/CO favors a true anti-HBc. A rise to 640 mIU/mL within 3 weeks of a single dose is a fast, strong secondary (memory) response, showing earlier exposure to HBsAg, so this is a resolved past infection. A person who had never met the virus usually makes little or no anti-HBs this soon after one dose. She is considered immune and needs no further doses, but her anti-HBc should be recorded, because strong immunosuppression later in life could reactivate the virus.

   • A: IgM anti-HBc is nonreactive, which excludes the core window.
   • B: HBsAg is nonreactive and HBV DNA is not detected, so occult infection is unlikely.
   • C: A primary response to one dose is usually low or absent at 3 weeks, not 640 mIU/mL.

3. Question 3 · Hard

   An unvaccinated 30-year-old man is followed after a sexual exposure to a partner with hepatitis B; week 0 is the day of exposure. His serial results are shown (ALT reference below 40 U/L). The week-44 results are best interpreted as:

   

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   1. AChronic infection after HBeAg seroconversion
   2. BWindow period before anti-HBs appears
   3. CReactivation of a past, resolved infection
   4. DAcute infection that is still resolving

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   Answer: A · Chronic infection after HBeAg seroconversion

   All markers were negative at week 0, and by week 8 he had acute hepatitis B: HBsAg, HBeAg and IgM anti-HBc with a very high ALT. HBsAg has now persisted from week 8 to week 44, more than 6 months, without anti-HBs appearing, which defines chronic infection. The loss of HBeAg and the appearance of anti-HBe at week 44 is HBeAg seroconversion, usually with lower viral replication and a falling ALT, but he remains infected. He needs HBV DNA and long-term follow-up, and his contacts should be offered vaccination.

   • B: The window period has no HBsAg, and his HBsAg is still positive.
   • C: His week-0 sample had no anti-HBc, so there was no earlier infection to reactivate.
   • D: HBsAg that persists for more than 6 months means the infection has become chronic.

4. Question 4 · Medium

   The chart shows the usual course of hepatitis B markers in an acute infection that resolves. Which results are expected at the time marked X?

   

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   1. AHBsAg neg, IgM anti-HBc pos, anti-HBs neg
   2. BHBsAg neg, IgM anti-HBc pos, anti-HBs pos
   3. CHBsAg pos, IgM anti-HBc pos, anti-HBs neg
   4. DHBsAg neg, IgM anti-HBc neg, anti-HBs pos

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   Answer: A · HBsAg neg, IgM anti-HBc pos, anti-HBs neg

   At X, about 26 weeks after exposure, HBsAg has fallen below the cut-off but anti-HBs has not yet risen above it. This gap is the window period, and IgM anti-HBc (with total anti-HBc) is then the only marker of the recent infection. A patient tested at this time with HBsAg alone would be missed. This is one reason anti-HBc testing is added when hepatitis B is suspected and HBsAg is negative.

   • B: Anti-HBs only rises above the cut-off a few weeks after X.
   • C: HBsAg has already fallen below the cut-off at X.
   • D: IgM anti-HBc is still above the cut-off, and anti-HBs has not yet appeared.

5. Question 5 · Medium

   Pre-employment hepatitis B results for four new staff members are shown. Which person is immune because of a past infection rather than vaccination?

   

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   1. AStaff B
   2. BStaff A
   3. CStaff D
   4. DStaff C

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   Answer: D · Staff C

   Only natural infection produces anti-HBc, because the vaccine contains HBsAg alone. Staff C has no HBsAg, has total anti-HBc without IgM anti-HBc, and has a protective anti-HBs: a resolved past infection with immunity. Staff A has anti-HBs alone, the pattern of vaccination. Staff B carries HBsAg with IgM-negative anti-HBc, which suggests chronic infection, and Staff D has no markers and should be vaccinated.

   • A: HBsAg with IgM-negative anti-HBc suggests chronic infection, not immunity.
   • B: Anti-HBs without anti-HBc is the pattern of vaccination.
   • C: No markers at all means Staff D is susceptible.

6. Question 6 · Hard

   A newly hired laboratory technologist completed three doses of hepatitis B vaccine. Anti-HBs 6 weeks after the last dose is 4 mIU/mL (protective at 10 mIU/mL or more). Following CDC guidance, what is the best next step?

   1. AGive HBIG now and repeat it every year
   2. BLabel her a nonresponder; give no more vaccine
   3. CGive a second vaccine series, then retest anti-HBs
   4. DRecord her as protected and recheck in 5 years

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7. Question 7 · Hard

   A 46-year-old man has had HBsAg for 15 years. Over the past year his ALT has risen to 180 U/L (reference below 40 U/L), but HBV DNA is only 40 IU/mL. HBeAg nonreactive, anti-HBe reactive, anti-HCV nonreactive; alcohol intake is minimal. Which test should be done next?

   1. AHBV genotyping
   2. BIgM anti-HAV
   3. CTotal anti-HDV
   4. DAnti-HBs level

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8. Question 8 · Medium

   At premarital screening, a 27-year-old man is HBsAg reactive. Seven months later: HBsAg reactive, total anti-HBc reactive, IgM anti-HBc nonreactive, anti-HBs nonreactive, ALT normal. These results show:

   1. AResolved infection with immunity
   2. BAcute hepatitis B infection
   3. CChronic hepatitis B infection
   4. DRecovery phase of acute infection

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9. Question 9 · Medium

   A hospital wants to know which new staff have ever been infected with hepatitis B, whether or not they were vaccinated. Which single marker best shows past or present infection?

   1. AAnti-HBs level
   2. BTotal anti-HBc
   3. CHBsAg
   4. DHBeAg

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10. Question 10 · Hard

    A weakly reactive HBsAg screen is sent for confirmatory neutralization. The kit states that a fall in signal of 50% or more after adding anti-HBs confirms HBsAg. Untreated aliquot: S/CO 4.0. Aliquot treated with anti-HBs: S/CO 1.4. The result is:

    1. A35% fall; not confirmed
    2. B186% fall; HBsAg confirmed
    3. CNot confirmed; treated S/CO is still above 1.0
    4. D65% fall; HBsAg confirmed

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11. Question 11 · Hard

    Results in a man known to carry HBsAg for many years: HBsAg reactive (confirmed), anti-HBs 35 mIU/mL, total anti-HBc reactive, IgM anti-HBc nonreactive, HBeAg nonreactive, HBV DNA 25,000 IU/mL, ALT 75 U/L (reference below 40 U/L). The best interpretation is:

    1. AAcute infection on top of an old resolved one
    2. BOngoing chronic infection despite the anti-HBs
    3. CVaccine immunity with a falsely reactive HBsAg
    4. DRecovery, with anti-HBs signalling clearance

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12. Question 12 · Hard

    A 22-year-old woman infected at birth has these results at three visits over a year: HBsAg reactive, HBeAg reactive, HBV DNA about 10^8 IU/mL, ALT always within the reference interval, minimal fibrosis. Which EASL phase is this?

    1. AHBeAg-negative chronic hepatitis
    2. BHBeAg-positive chronic hepatitis
    3. CHBeAg-positive chronic infection
    4. DAcute hepatitis B infection

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13. Question 13 · Medium

    In an HBsAg-positive pregnant woman, which result best identifies a high risk that the baby will be infected despite vaccination at birth?

    1. AALT within the reference interval
    2. BIgM anti-HBc nonreactive
    3. CAnti-HBe reactive with HBeAg nonreactive
    4. DHBV DNA above 200,000 IU/mL

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14. Question 14 · Medium

    Hepatitis B vaccination also protects against hepatitis D. Why?

    1. AHDV is a genotype of hepatitis B
    2. BThe vaccine contains HDV delta antigen
    3. CHDV uses HBsAg as its own envelope
    4. DAnti-HBs cross-reacts with delta antigen

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15. Question 15 · Hard

    During pre-employment screening, a nurse who had a hepatitis B booster dose 7 days ago has a weakly reactive HBsAg, confirmed by neutralization. Total anti-HBc is nonreactive, anti-HBs 850 mIU/mL, HBV DNA not detected and ALT normal. What is the most likely explanation?

    1. AEarly acute hepatitis B infection
    2. BOccult hepatitis B infection
    3. CHBsAg escape mutant infection
    4. DTransient antigenemia from the vaccine dose

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16. Question 16 · Hard

    At premarital screening, a 24-year-old woman's fiancé is found to have chronic hepatitis B. Her results: HBsAg nonreactive, total anti-HBc nonreactive, anti-HBs below 2 mIU/mL. She has no vaccination record and her ALT is normal. The most appropriate action is:

    1. AVaccinate her, then check anti-HBs 1-2 months later
    2. BRepeat all three markers in 6 months before deciding
    3. CGive HBIG only, as vaccine will not work in her
    4. DReport her as immune and advise no further action

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17. Question 17 · Medium

    Which set of results best fits acute hepatitis B in a patient with jaundice?

    1. AHBsAg +, IgM anti-HBc +, anti-HBs −
    2. BHBsAg −, total anti-HBc +, anti-HBs +
    3. CHBsAg +, IgM anti-HBc −, total anti-HBc +
    4. DHBsAg −, anti-HBc −, anti-HBs +

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18. Question 18 · Hard

    A 3-year-old child of an HBsAg-positive mother received HBIG and a full vaccine course. Now: HBsAg nonreactive by the laboratory's assay, anti-HBs 180 mIU/mL, total anti-HBc reactive, HBV DNA 3,000,000 IU/mL; a different HBsAg assay is reactive. The most likely explanation is:

    1. ATransient antigen from the vaccine doses
    2. BSuccessful protection after vaccination
    3. CAn HBsAg escape mutant infection
    4. DMaternal antibody and a false-positive DNA

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19. Question 19 · Medium

    A woman has been HBsAg reactive for 12 years. Over the past year: HBeAg nonreactive, anti-HBe reactive, HBV DNA 600-900 IU/mL and ALT always within the reference interval. Using EASL terms, which phase is this?

    1. AResolved hepatitis B infection
    2. BHBeAg-positive chronic infection
    3. CHBeAg-negative chronic infection
    4. DHBeAg-negative chronic hepatitis

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20. Question 20 · Easy

    After a hepatitis B vaccine series, the anti-HBs level generally taken as protective is:

    1. A50 mIU/mL or more
    2. B1 mIU/mL or more
    3. C100 mIU/mL or more
    4. D10 mIU/mL or more

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21. Question 21 · Medium

    A woman's fiancé has chronic hepatitis B. Her premarital results: HBsAg nonreactive, total anti-HBc reactive, anti-HBs 240 mIU/mL. She has never been vaccinated. The best interpretation is:

    1. AChronic infection with low-level virus
    2. BImmune after a past, resolved infection
    3. CSusceptible; she needs the vaccine series
    4. DImmune from earlier hepatitis B vaccination

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