@article {Feruccijrheum.130293, author = {Elizabeth D. Ferucci and Erika Darrah and Irene Smolik and Tammy L. Choromanski and David B. Robinson and Marianna M. Newkirk and Marvin J. Fritzler and Antony Rosen and Hani S. El-Gabalawy}, title = {Prevalence of Anti-Peptidylarginine Deiminase Type 4 Antibodies in Rheumatoid Arthritis and Unaffected First-degree Relatives in Indigenous North American Populations}, elocation-id = {jrheum.130293}, year = {2013}, doi = {10.3899/jrheum.130293}, publisher = {The Journal of Rheumatology}, abstract = {Objective To determine whether anti-peptidylarginine deiminase type 4 (PAD4) antibodies were present in first-degree relatives (FDR) of patients with rheumatoid arthritis (RA) in 2 indigenous North American populations with high prevalence of RA. Methods Participants were recruited from 2 indigenous populations in Canada and the United States, including patients with RA (probands), their unaffected FDR, and healthy unrelated controls. Sera were tested for the presence of anti-PAD4 antibodies, anticyclic citrullinated peptide (anti-CCP) antibodies, and rheumatoid factor (RF). HLA-DRB1 subtyping was performed and participants were classified according to number of shared-epitope alleles present. Results Antibodies to PAD4 were detected in 24 of 82 (29.3\%) probands; 2 of 147 (1.4\%) relatives; and no controls (p \< 0.0001). Anti-CCP was present in 39/144 (27.1\%) of the relatives, and there was no overlap between positivity for anti-CCP and PAD4 in the relatives. In RA patients, anti-PAD4 antibodies were associated with disease duration (p = 0.0082) and anti-CCP antibodies (p = 0.008), but not smoking or shared-epitope alleles. Conclusion Despite a significant prevalence of anti-CCP in FDR, anti-PAD4 antibodies were almost exclusively found in established RA. The prevalence of anti-PAD4 antibodies in RA is similar to the prevalence described in other populations and these autoantibodies are associated with disease duration and anti-CCP in RA.}, issn = {0315-162X}, URL = {https://www.jrheum.org/content/early/2013/07/23/jrheum.130293}, eprint = {https://www.jrheum.org/content/early/2013/07/23/jrheum.130293.full.pdf}, journal = {The Journal of Rheumatology} }