PRTN3 and rheumatoid arthritis: Notably, ACPA(+) individuals, especially those with higher titers of the common clinically used ACPA assay ‘anti-cyclic citrullinated peptide antibody (anti-CCP)3, have a significantly elevated risk of developing future classified RA, and thus these individuals can be designated to be in an “At-Risk” state, and defined as such for studies1,2,4–8.