Epitope mapping on zinc finger protein (706ZNF706), GABA(A) receptor-associated protein-like 2 (GABARAPL2) and within BGCN homolog (WIBG). Sera from patients with early RA, and from patients with ankylosing spondylitis (AS), psoriatic arthritis (PsA), systemic lupus erythematosus (SLE), and healthy controls were tested for binding to ZNF706, GABARAPL2 and WIBG peptides by ELISA. After washing, peroxydase-conjugated anti-human immunoglobulin G was added. Optical density (OD) was read at 405 nm. Background OD was obtained by adding each serum to a well without peptide. Positive sera were defined by an OD value higher than twice the background OD (yellow).