Finally, as anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative RA are considered as different disease subsets with differences in the underlying pathophysiology, analyses were stratified for ACPA-positive and ACPA-negative RA to explore if there are differences in the chronological order in which different articular tissues become inflamed. This evidence concerns the gene PRTN3 and rheumatoid arthritis.