PRTN3 and rheumatoid arthritis: In our extended analysis, we found that the SE association was significantly stronger in the presence of ACPA reactive with Cit-Fibβ60–74, Cit-peptide-5, Cit-peptide-Z1, Cit-Vim60–75, CEP-1, and Cit-Vim2–17, than in the absence of these six ACPA fine-specificities (Additional file 7); two of these ACPA fine-specificities (Cit-Fibβ60–74 and Cit-Vim60–75) also showed significant associations with SE in anti-CCP2-negative RA.