## Anti-CCP Antibody in Rheumatoid Arthritis **Key Point:** Anti-CCP antibodies are the most specific serological marker for RA, with specificity >95%, and are present in 60–70% of RA patients, including those who are rheumatoid factor (RF) negative. **High-Yield:** Anti-CCP positivity is associated with: - More severe, erosive joint disease - Worse functional outcomes - Greater radiographic progression - Presence even in early/seronegative RA ### Comparison of RA Serological Markers | Marker | Specificity | Sensitivity | Clinical Significance | | --- | --- | --- | --- | | Anti-CCP | >95% | 60–70% | Most specific; predicts erosive disease | | Rheumatoid Factor (RF) | 80–85% | 70–80% | Less specific; can be positive in other autoimmune diseases | | ANA | 40–60% in RA | Variable | Non-specific; more associated with SLE | | ASMA | <5% in RA | N/A | Associated with autoimmune hepatitis, not RA | **Clinical Pearl:** A patient who is RF-negative but anti-CCP positive has "seronegative RA" by traditional RF criteria but is still at high risk for erosive disease and should be treated aggressively. **Mnemonic:** **CCP = Citrullinated peptide = Cartilage-damaging Predictor** — anti-CCP predicts more severe, erosive disease.
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