Furthermore, PAD activity in fresh, untreated SF samples from patients with RA strongly correlated with not only the levels of extracellular DNA (ρ = 0.8, P < 0.0001) (Figure 5D) but also the neutrophil counts (ρ = 0.8, P = 0.002) and total cell counts (ρ = 0.72, P = 0.002) (see Supplementary Figures 1D and E, available on the Arthritis & Rheumatology web site at http://onlinelibrary.wiley.com/doi/10.1002/art.39313/abstract). This evidence concerns the gene PADI4 and rheumatoid arthritis.