CRP and rheumatoid arthritis: Spearman correlation analyses between exosomal miR-204-5p levels and disease activity of the RA patients in the validation group showed that exosomal miR-204-5p expression was inversely correlated with rheumatoid factor (RF) (R = −0.44, P = 0.028), erythrocyte sedimentation rate (ESR) (R = −0.31, P = 0.032), and C-reactive protein (CRP) (R = −0.49, P = 0.020) but not the disease activity score using 28 joint counts (DAS28) and cyclic citrullinated peptide antibody (CCP) (Fig. 1f).