Significant positive correlations were found between D-dimer level and disease activity index in all RA patients, such as ESR (r = 0.586, p < 0.001), CRP (r = 0.574, p < 0.001), DAS28 (r = 0.414, p < 0.001), IgG (r = 0.326, p < 0.001), IgA (r = 0.318, p < 0.001), and IgM (r = 0.261, p < 0.001). This evidence concerns the gene CRP and rheumatoid arthritis.