One Step HBsAg Test is a rapid direct binding test for the visual detection of hepatitis B surface antigen (HBsAg) in serum (whole blood) as an aid in the diagnosis of hepatitis B infection. One Step HBsAg Test is based on the principle of sandwich immunoassay for determination of HBsAg in serum. Monoclonal and polyclonal antibodies are employed to identify HBsAg specifically.