Recognition of BRAF peptides in RA patients and controls. Anti-BRAF autoantibodies from the sera of RA, AS, PsA patients and healthy controls were tested for binding to BRAF peptides by ELISA. After washing, peroxydase conjugated anti-human IgG was added. Optical density was read at 405 nm. Background OD was obtained by adding each serum to a well without peptide. Positive sera were defined by OD value higher than twice background OD.