Which lab is most-specific for Rheumatoid Arthritis?

• A. RF
• B. Anti-Mi-2
• C. Anti-CCP
• D. HLA-B27

Answer: (C)

Anti-CCP antibodies are highly specific for rheumatoid arthritis, making this lab the best choice to confirm RA. While rheumatoid factor is common in RA, it also appears in many other conditions and even in healthy people, so it’s not as specific. Anti-Mi-2 antibodies point to dermatomyositis, not RA. HLA-B27 is associated with seronegative spondyloarthropathies, such as ankylosing spondylitis, rather than RA. The CCP test detects antibodies to citrullinated proteins, which are closely linked to RA pathogenesis, and its presence strongly supports RA, even when RF is negative.