What laboratory test is more specific for rheumatoid arthritis than rheumatoid factor?

The laboratory test that is more specific for rheumatoid arthritis than rheumatoid factor is anti-citrullinated protein antibodies (anti-CCP).

Rheumatoid factor (RF) is an antibody that can be found in various autoimmune diseases and even in some healthy individuals, which reduces its specificity for rheumatoid arthritis. In contrast, anti-CCP antibodies are directed against citrullinated peptides, which are specifically associated with rheumatoid arthritis. The presence of these antibodies not only supports the diagnosis but is also indicative of a more severe disease course and potential joint erosion.

Anti-CCP testing is particularly valuable because it can be positive well before the clinical symptoms of rheumatoid arthritis become apparent, making it a useful tool for early diagnosis. Studies have shown that the presence of anti-CCP antibodies can significantly increase the likelihood of a patient having rheumatoid arthritis compared to RF alone.

The other options, such as ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein), are markers of inflammation but lack the specificity for rheumatoid arthritis, as they can be elevated in many inflammatory conditions. Antinuclear antibodies (ANA) are often associated with systemic lupus erythematosus and other autoimmune disorders rather than being specific to rheumatoid arthritis.