PRTN3 and arthritic joint disease: When comparing the findings of the present study with previous results, there is a difference in the percentage of triple positivity for anti-CarP, ACPA and RF: indeed, the percentage of triple-positive patients is lower among patients in the Norfolk Arthritis Register and higher in the early arthritis Leiden cohort compared to the present cohort of Italian patients with RA [12, 19]; this discrepancy could result from the different genetic background of the populations studied.