The reason why the ratio was more clinically meaningful than the absolute value of the titer might be that the antibodies detected by the anti-CCP2 assay contained antibodies which recognized the antigens not related to the pathology of RA, or contained antibodies that had weak affinity to the antigen, and that the effect of the antibody concentration increase by such antibody might be diluted by calculating the ratio. Here, AGBL2 is linked to rheumatoid arthritis.