The invention relates to a method for determining antigen-specific antibodies of immunoglobulin class G in the presence of immunoglobulins of class M in body fluids by incubation with at least two different receptors R1 and R2 and optionally additional receptors, wherein a bonding partner in monomer form is a substantial constituent of R2. The invention also relates to a reagent for determining an antigen-specific antibody of immunoglobulin class G and the use of bonding partners in monomer form for determining an antigen-specific antibody of immunoglobulin class G.
