Which laboratory finding is most specific for rheumatoid arthritis?

Which laboratory finding is most specific for rheumatoid arthritis?

• A. ESR
• B. RF
• C. ACPA (most specific)
• D. ANA

Answer: (C)

Anti-CCP antibodies (ACPA) are the most specific test for rheumatoid arthritis. They target citrullinated proteins that appear in the inflamed joint, and their presence strongly supports RA—often helping confirm the diagnosis, especially in early disease. Rheumatoid factor can be positive in many people without RA and in other autoimmune diseases, so it’s sensitive but not specific. ESR is a general marker of inflammation and rises in many conditions, not just RA. ANA points to systemic autoimmune diseases like lupus and is not specific for RA. Therefore, anti-CCP antibodies provide the strongest RA-specific diagnostic signal among these options.

Anti-CCP antibodies (ACPA) are the most specific test for rheumatoid arthritis. They target citrullinated proteins that appear in the inflamed joint, and their presence strongly supports RA—often helping confirm the diagnosis, especially in early disease.

Rheumatoid factor can be positive in many people without RA and in other autoimmune diseases, so it’s sensitive but not specific. ESR is a general marker of inflammation and rises in many conditions, not just RA. ANA points to systemic autoimmune diseases like lupus and is not specific for RA. Therefore, anti-CCP antibodies provide the strongest RA-specific diagnostic signal among these options.