Interestingly, MMP19 also correlated positively with CRP (ρ = 0.49 and P = 1.47 × 10–3) in ACPA– RA, but again, this association was absent in ACPA+ RA (ρ = 0.03 and P = 0.87) (Figure 2D; Supplementary Table S3). Here, MMP19 is linked to rheumatoid arthritis.