• Anti-citrullinated protein antibodies (ACPAs), antibodies that are directed against citrullinated

proteins, play a key role in the pathogenesis of RA. In the past decade, the anti-CCP test has been
widely used to detect ACPAs and diagnose RA. Although the anti-CCP test is around 95% specific,
around 20%-40% of RA patients are still anti-CCP negative.

• RA_CP was developed using anti-MCSM antibodies. Peptides with Multiple Citruline Similar

Motif (MCSM) were synthesized and used to produce anti-MCSM antibodies. Anti-MCSM
antibodies recognized MCSM in the citrullinated proteins, such as fibrogen, vimentin, and enolase,
found in RA patients. The RA_CP has a sensitivity of 86.0%, which is higher than the anti-CCP assay,
and a specificity of 96.3%.