In multiple variable analyses adjusted for sex, age at RA diagnosis, smoking ever status and presence of RF, six of the ACPA specificities remained significantly associated with increased risk of PF development, namely anti-Vim60–75 [OR 2.13 (95% CI 1.07, 4.50), P < 0.05], anti-Fibβ62–78 (72) [OR 2.43 (95% CI 1.20, 4.67), P < 0.01], anti-Fibα621–635 [OR 2.12 (95% CI 1.12, 3.85), P < 0.05], anti-Bla26 [OR1.92 (95%CI 1.05, 3.51), P < 0.05], anti-CII359–369 [OR 1.92 (95% CI 1.04, 3.56), P < 0.05] and anti-F4-CIT-R antibodies [OR 2.57 (95% CI 1.38, 4.79), P < 0.01] (data not shown). This evidence concerns the gene PRTN3 and rheumatoid arthritis.