CEACAM1 and rheumatoid arthritis: Additionally, the MFI of CEACAM1 were significantly higher in the CRP–positive RA group (median 1603, IQR 1,434–1,920) than in the CRP–negative RA group (median 1,534, IQR 1,055–1748) (p = 0.001) (Figure 3A).