Oscar HBs Ag ELISA detects HBs Ag (Hepatitis B Surface antigen) in human serum / plasma. It is available in 96T pack. Microwell strips are coated with monoclonal anti-HBsAg antibodies. Another polyclonal antibody to HBsAg is conjugated to horseradish peroxidase (HRP). The samples are added in the coated wells and incubated. After washing to remove unreacted and unbound material, polyclonal antibody-HRP conjugate is added. The wells are washed to remove unbound components. Bound enzyme is detected by adding substrate. The reaction is stopped after specified time with acid and absorbance is determined for each well at 450 nm with an ELISA reader. The cutoff value is calculated by the given formula and absorbances of all the wells are compared with the cutoff value. Any sample having absorbance more than the cutoff value is considered reactive.