From the Guidelines
A positive Hepatitis B surface antigen (HBsAg) indicates active Hepatitis B virus (HBV) infection, either acute or chronic, and all HBsAg-positive persons are infectious. Management depends on disease phase and severity. For chronic HBV, antiviral therapy is recommended for patients with elevated liver enzymes, high viral load (HBV DNA >2,000 IU/mL), or evidence of liver damage, as stated in the 2018 guidelines by the Advisory Committee on Immunization Practices 1. First-line treatments include entecavir (0.5mg daily) or tenofovir (either tenofovir disoproxil fumarate 300mg daily or tenofovir alafenamide 25mg daily), which have high barriers to resistance and excellent safety profiles.
The interpretation of serologic markers is crucial in determining the phase of HBV infection.
- HBsAg and IgM anti-HBc indicate acute infection
- HBsAg and IgG anti-HBc indicate chronic infection
- Isolated anti-HBc may indicate past infection or occult HBV infection
- Anti-HBs indicates immunity to HBV infection, either from vaccination or past infection 1.
Treatment is typically long-term, often lifelong, as complete cure is rare. Regular monitoring includes:
- Liver function tests every 3-6 months
- HBV DNA levels every 6-12 months
- Periodic assessment for hepatocellular carcinoma with ultrasound and alpha-fetoprotein testing. All patients, regardless of treatment status, should avoid alcohol, maintain a healthy weight, and be vaccinated against Hepatitis A. Family members and close contacts should be screened for HBV and vaccinated if susceptible. The goal of treatment is to suppress viral replication, prevent progression to cirrhosis and liver cancer, and reduce transmission risk, as outlined in the 2015 treatment algorithm for the management of chronic hepatitis B virus infection 1. HBsAg positivity occurs because the virus produces this surface protein during active infection, which circulates in the bloodstream and serves as a key diagnostic marker.
From the Research
Hepatitis B Surface Antigen (HBsAg) Indication
- A positive Hepatitis B surface antigen (HBsAg) indicates an active Hepatitis B infection 2.
- HBsAg is the hallmark of HBV infection and is the first serological marker to appear in acute hepatitis B 2.
- Persistence of HBsAg for more than 6 months suggests chronic HBV infection 2.
Management of HBsAg Positive Patients
- Monitoring the serum HBV DNA level is valuable for assessing liver disease activity, differentiating other etiologies of hepatitis activity in HBV carriers, predicting risk of HCC development or liver-related mortality, deciding to administer antiviral therapy, determination of the response to antiviral treatment, predicting the risk of developing drug resistance, and detecting the emergence of drug-resistant mutants 2.
- HBsAg quantification can be used to identify patients who will not benefit from therapy as early as week 12 on therapy, so that treatment may be stopped or switched 3.
- HBsAg levels and rates of decline could inform assessment, management and prediction of outcomes in chronic HBV infection 4.
HBsAg Levels and Disease Outcomes
- High levels of HBsAg are suggestive of low fibrosis and immune tolerance in hepatitis B e antigen (HBeAg) positive patients 5.
- Low levels of HBsAg indicate a lower risk for HCC and inactive carrier state in HBeAg negative patients 5.
- HBsAg titres are significantly associated with various virological markers including serum HBV DNA, HBcrAg, HBeAg, HBV RNA levels, intrahepatic covalently closed circular DNA (cccDNA) and intrahepatic HBsAg expression 4.