The new hepatitis B surface antigen (HBsAg) quant test enables physicians to assess a patient’s response to chronic hepatitis B treatment. As chronic hepatitis B remains endemic in many parts of Asia, experts from across the region are meeting at the 21st Asian Pacific Association for the Study of the Liver (APASL) annual congress in Bangkok, Thailand to discuss advances in the management of this devastating disease, which is a major cause of liver cirrhosis and cancer. One key advance is the availability of a new quantitative test for monitoring a patient’s response to hepatitis B therapy, launched during the congress by Roche Diagnostics. The test measures the amount of hepatitis B surface antigen (HBsAg), a marker on the surface of the hepatitis B virus, in a patient’s blood. This, in combination with HBV DNA testing, enables clinicians to provide tailored treatment approaches for chronic hepatitis B patients. HBsAg quantitative testing represents a simple and reliable means of assessing how well the body’s own immune system is combating the hepatitis B virus. It allows clinicians to monitor and assess a patient’s response to pegylated interferon (PEG-IFN) therapy, thereby confidently predict treatment success early. This is particularly important as studies show that one in three respond to the PEG-IFN treatment. In addition, there is evidence that HBsAg levels in combination with HBV DNA levels, can be used to distinguish patients who do not require therapy (inactive carriers) from those who would benefit from treatment.