Recombinant centromere protein B is bound to microwells. Antibodies against this antigen, if present in diluted serum or plasma, bind to the respective antigen.Washing of the microwells removes unspecific serum and plasma components. Horseradish peroxidase (HRP) conjugated anti-human IgG immunologically detects the bound patient antibodies forming a conjugate/antibody/antigen complex. Washing of the microwells removes unbound conjugate. An enzyme substrate in the presence of bound conjugate hydr