From the Guidelines
Hepatitis B surface antigen (HBsAg) is a protein found on the surface of the hepatitis B virus that indicates an active hepatitis B infection, and when detected, further testing is recommended to determine the stage of infection and need for treatment, as chronic hepatitis B can lead to serious liver complications including cirrhosis and liver cancer 1.
Key Points
- HBsAg typically appears in the blood 1-10 weeks after exposure to the virus and, if it persists for more than 6 months, indicates a chronic infection 1.
- For those who test positive for HBsAg, further testing is recommended, including hepatitis B e antigen (HBeAg), hepatitis B DNA levels, and liver function tests to determine the stage of infection and need for treatment 1.
- Treatment options for chronic hepatitis B include antiviral medications such as entecavir, tenofovir, or pegylated interferon, depending on viral load, liver damage, and other factors 1.
- Regular monitoring is essential as chronic hepatitis B can lead to serious liver complications including cirrhosis and liver cancer 1.
- Vaccination is available to prevent hepatitis B infection and is recommended for those at risk who test negative for the virus 1.
Management
- Patients with chronic HBV receiving any systemic anticancer therapy should receive antiviral prophylactic therapy for the duration of anticancer therapy, as well as for at least 12 months after receipt of the last anticancer therapy 1.
- Monitoring recommendations include checking alanine aminotransferase (ALT) and HBV DNA level at baseline prior to or at the beginning of their anticancer therapy, as well as every 6 months during antiviral therapy 1.
- Coordination of care with a clinician experienced in HBV management is highly recommended for patients with chronic HBV, especially to monitor for withdrawal flares, determine monitoring and antiviral therapy after the cessation of anticancer therapy, and evaluate for advanced liver disease such as cirrhosis or liver cancer 1.
From the Research
Hepatitis B Surface Antigen
- Hepatitis B surface antigen (HBsAg) is a marker of hepatitis B virus (HBV) infection, and its presence indicates that the person is infectious 2.
- The level of HBsAg can be used to monitor the effectiveness of treatment and predict the risk of relapse after treatment is stopped 3.
- A higher level of HBsAg at baseline or at the end of treatment is associated with a higher risk of relapse after entecavir therapy for chronic HBV infection 3.
Treatment and HBsAg Levels
- Tenofovir and entecavir are the most effective antiviral agents for reducing HBsAg levels in patients with chronic HBV infection 4.
- Tenofovir alafenamide, a new prodrug of tenofovir, has been shown to reduce HBsAg levels more effectively than entecavir in some patients 5.
- Combination therapy with pegylated interferon-α and nucleoside/nucleotide analogs, such as entecavir or tenofovir, may also be effective in reducing HBsAg levels, but more research is needed to confirm this 6.
Clinical Significance of HBsAg Levels
- The level of HBsAg can be used to guide the timing of cessation of entecavir treatment in patients with chronic HBV infection 3.
- A decrease in HBsAg level from month 12 of treatment until the end of treatment is associated with a lower risk of relapse after treatment is stopped 3.
- HBsAg levels may also be used to monitor the effectiveness of treatment and predict the risk of hepatocellular carcinoma and cirrhosis in patients with chronic HBV infection 2.