Furthermore, SC ACPA positivity remained significantly prognostic for progression in Cox regression analyses within the RF negative group in both the Karolinska risk RA cohort (HR 2.1 95 %CI 1.1–4.0, p = 0.02) and the TIRx cohort (HR 2.8 95 %CI 1.2–6.6, p = 0.02). Here, PRTN3 is linked to rheumatoid arthritis.