We aimed to jointly investigate the role of antipeptidyl arginine deiminase type 4 antibodies (anti-PAD4) and polymorphisms in the 
Serum IgG autoantibodies to human recombinant PAD4 were identified by DELFIA technique in 745 patients with RA (366 available from previous studies). Genotyping of 
Anti-PAD4 antibodies were detected in 193 (26%) of 745 patients with RA; 149 (77%) of these were also ACPA-positive. No association was observed between anti-PAD4 status and clinical characteristics, 
Taken together, the results from these combined serological, genetic, and clinical analyses suggest that anti-PAD4 appears to be a bystander autoantibody with no current clinical utility in RA.