HBsAg ELISA kits are assays designed to detect the surface antigen of Hepatitis B virus. Hepatitis B is a double-stranded DNA virus that can cause Hepatitis B disease in acute or chronic form. The virus has also been associated with cirrhosis and hepatic carcinoma. HBsAg is a protein embedded on the outer envelope of the virus. It was the first Hepatitis B protein to be discovered and contains small (S), medium (M) and large (L) proteins. Visit the supplier page for more information about detection range, quantity and reactivity.