"Identification of an antibody against a novel peptide from Porphyromonas gingivalis as a biomarker for rheumatoid arthritis".

Current serological markers for rheumatoid arthritis (RA) lack sensitivity in early or seronegative disease. We evaluated anti-BR1 antibodies, targeting a Porphyromonas gingivalis RgpA-derived peptide, as a novel biomarker. From 15 peptides screened in a training cohort, BR1 showed the highest diagnostic potential (AUC = 0.9553). In an independent validation cohort, anti-BR1 demonstrated an AUC of 0.7668, with 58.6 % sensitivity and 97.0 % specificity based on a ROC-derived cutoff. Anti-BR1 antibodies were detected in 82 of 140 (58.6 %) RA cases, including 35 of 58 (60.3 %) seronegative patients, and in 16 of 38 (42.1 %) early arthritis (EA) cases, outperforming RF and ACPA. Combining anti-BR1 with RF and ACPA increased the diagnostic yield from 58.6 % to 83.6 % in RA, and from 26.3 % to 55.3 % in EA.