The combined model of either marker and covariates provided a significantly (p < 0.01) better separation of OA and E-RA with differences (SE) to covariates alone of 0.05 (0.02) and 0.08 (0.02) CRP and CRPM respectively (Fig. 2A, Table S2), and in separating OA and MS-RA with differences of 0.08 (0.02) for both markers (Fig. 2B, Table S3). Here, CRP is linked to rheumatoid arthritis.