The Epstein–Barr virus viral-capsid antigen (EBV-VCA) is the viral protein that forms the viral capsid of the Epstein–Barr virus. It is the antigen targeted by anti-VCA antibodies. Such antibodies can be used in serology to diagnose infectious mononucleosis. In cases with primary infection, the sensitivity of IgG (immunoglobulin) and IgM anti-VCA testing has been estimated to be 100% reliable.
Elevated Anti-VCA IgM indicates acute infection.
Elevated Anti-VCA IgG indicates prior infection.
References
Epstein–Barr virus viral-capsid antigen Wikipedia(Text) CC BY-SA