http://liver.stanford.edu/Edu/Edu_whatcarr.php
Asian Liver Center at Stanford University
If your hepatitis B surface antigen (HBsAg) is positive, you are a hepatitis B carrier and have chronic hepatitis B. Although many hepatitis B carriers have no symptoms and feel "healthy," they still run a high risk of developing liver cancer or cirrhosis. It is important for carriers to check every six months for blood levels of serum transaminase (ALT or SGPT) for liver damage, and alpha-fetoprotein (AFP) to screen for liver cancer. After 30 years of age, an annual ultrasound examination of the liver is recommended. Either test alone can miss the diagnosis of a small liver cancer.