This screening test is used to detect Hepatitis B surface antigen (HBsAg). HBsAg is a protein antigen produced by the Hepatitis B virus (HBV). This antigen is the earliest indicator of acute hepatitis B and frequently identifies infected people before symptoms appear. HbsAg disappears from the blood during the recovery period. A positive report indicates HBV infection, this needs to be further confirmed with ELISA or Real time PCR.