How to interpret the results of HBV tests for diagnosis and its follow-up?

Biên soạn: TS.BS Trần Ngọc Tuấn – ĐV Sinh học phân tử – Bệnh viện Đa khoa Gia Đình Đà Nẵng.

1. Hepatitis B Surface Antigen (HBsAg):
   • Definition: HBsAg is a protein on the surface of the HBV.
   • Interpretation:
     • Positive HBsAg: Indicates acute or chronic HBV infection. The person is infectious.
     • Transient Positive HBsAg: Within 30 days after a dose of hepatitis B vaccine (HepB), HBsAg might be transiently positive.
   • Clinical Action: Link the patient to hepatitis B care.
2. Hepatitis B Surface Antibody (anti-HBs):
   • Definition: Presence of anti-HBs indicates recovery and immunity from HBV infection.
   • Development:
     • After successful vaccination against HBV.
     • Also in those who have recovered from natural infection.
   • Clinical Action: No further action needed unless anti-HBs levels decline over time (common among vaccine responders).
3. Total Antibody to Hepatitis B Core Antigen (anti-HBc):
   • Definition: Appears during acute hepatitis B and persists for life.
   • Indicates:
     • Previous or ongoing HBV infection (time frame undefined).
     • Not present in individuals with immunity from HBV vaccination.
   • Clinical Action: based on other markers.
4. IgM Antibody to Hepatitis B Core Antigen (IgM anti-HBc):
   • Definition: Positivity indicates recent (<6 months) HBV infection.
   • Clinical Action: Order when acute HBV infection is suspected.

5. Interpretation Scenarios:

1. • Acute Infection:
     • HBsAg Positive
     • Total anti-HBc Positive
     • IgM anti-HBc Positive
     • Anti-HBs Negative
     • Action: Link to hepatitis B care.
   • Chronic Infection:
     • HBsAg Positive
     • Total anti-HBc Positive
     • IgM anti-HBc Negative
     • Anti-HBs Negative
     • Action: Link to hepatitis B care.
   • Resolved Infection:
     • HBsAg Negative
     • Anti-HBs Positive
     • Total anti-HBc Positive
     • Action: Counsel about HBV infection reactivation risk.
   • Immune from Prior Vaccination:
     • HBsAg Negative
     • Anti-HBs Positive
     • Total anti-HBc Negative
     • Action: If documented complete vaccination, no further action. Otherwise, complete vaccine series.
   • Occult Infection:
     • HBsAg Negative
     • Anti-HBs Negative
     • Total anti-HBc Positive
     • Action: Counsel about HBV infection reactivation risk and link to hepatitis B care.

Interpretation of hepatitis B laboratory results                                                           
 Remember that interpreting these markers requires clinical judgment, and consultation with a healthcare provider is essential for accurate diagnosis and management.

Occult hepatitis B Infection (OBI) 

1. Definition:

1. • OBI refers to the presence of replication-competent hepatitis B virus (HBV) DNA in the liver and/or blood despite a negative hepatitis B surface antigen (HBsAg) result using currently available assays.
   • In other words, individuals with OBI do not show detectable HBsAg but still harbor HBV at a molecular level.

2. Prevalence and Risk Factors:

1. • OBI prevalence is challenging to estimate due to variations in testing sensitivity, populations studied, and blood sample testing.
   • It is more common in developing countries, especially where hepatitis B is endemic.
   • Immigrants in developed countries also contribute to the global impact of OBI.

3. Clinical Implications:

1. • Reactivation Risk: OBI is crucial in preventing reactivation of HBV infection, especially in patients receiving treatment for HIV, hepatitis C virus, or immunosuppressive therapy.
   • Mortality Prevention: Recognizing OBI helps prevent mortality associated with reactivation during immunosuppression.

4. Detection and Differentiation:

1. • Improved detection methods allow identification of HBV DNA in serum and liver tissue.
   • Understanding genetic variations of HBV aids in distinguishing overt (visible) from occult infection.

5. Clinical Outcomes:

1. • Recent research suggests that OBI may play a role in clinical outcomes such as chronic liver disease and hepatocellular carcinoma.
   • OBI-related morbidity and mortality are areas of ongoing study.

6. Policy Implications:

1. • Enhanced awareness and accurate detection methods will shape policies regarding therapeutics and preventive strategies for OBI.

In summary, OBI represents a hidden reservoir of HBV, and its impact extends beyond the absence of HBsAg. Healthcare policies must consider OBI in both preventive and therapeutic contexts.

References:

1. Interpretation of Hepatitis B Serologic Test Results. https://www.cdc.gov/hepatitis/hbv/interpretationOfHepBSerologicResults.htm. 2023.
2. https://www.cdc.gov/hepatitis/statistics/surveillanceguidance/docs/viral-hepatitis-surveillance-table-3-1_508.pdf
3. Hep B Foundation. https://www.hepb.org/prevention-and-diagnosis/diagnosis/understanding-your-test-results/. 2024.
4. Prevention of Hepatitis B Virus Infection in the United States: Recommendations of the Advisory Committee on Immunization Practices. https://www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6701-H.PDF. 2018
5. https://link.springer.com/article/10.1007/s11901-020-00549-3.
6. Occult Hepatitis B Virus Infection. https://ejmcm.com/uploads/paper/33b2a9865bf2731a97d69e7ae502ecf4.pdf. 2021