Full details of the study participants are included in the Methods section but, in brief, as part of the Targeting Immune Responses for Prevention of Rheumatoid Arthritis (TIP-RA) Collaborative we evaluated 97 participants who exhibited ACPA positivity by the commercial anti-CCP3 ELISA assay (IgG) (Inova Diagnostics, Inc., San Diego, CA; positive level >=20 units) who at their baseline study visit did not have historical or current examination evidence of IA; these participants are designated herein as “At-Risk”. Here, PRTN3 is linked to rheumatoid arthritis.