Five assays had unspecific signal for both IgM and IgG in a few up to a majority of the RA samples (test C: IgM 19/20, IgG 8/20; test D: IgM 19/20, IgG 2/20; test M: IgM 4/20, IgG 3/20; test N: IgM 6/20, IgG 1/20; and test P: IgM 1/20, IgG 1/20). Here, CD40LG is linked to rheumatoid arthritis.