Correlation of Porphyromonas gingivalis antibody levels and standard rheumatoid arthritis biomarkers. In the patients with early rheumatoid arthritis (RA), the levels of autoantibodies (anti-cyclic citrullinated peptide (anti-CCP) (A) and rheumatoid factor (RF)) and inflammatory markers (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)) (B) were compared at study entry in the 17 patients with positive Porphyromonas gingivalis (Pg) antibody responses and in the 33 patients with negative Pg antibody reactivity, as shown in the left panels. In the right panels, the levels of each RA biomarker are correlated with Pg immunoglobulin G antibody levels (Pearson correlation coefficients). Median values and interquartile ranges are shown, and the shaded regions represent normal values. Ab: antibody; OD: optical density.