## Serological Markers 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. ### Anti-CCP Antibodies - **Specificity:** >95% for RA (higher than rheumatoid factor) - **Sensitivity:** 60–70% in established RA - **Prognostic value:** Present in seronegative RA; predicts erosive disease and poor prognosis - **Clinical use:** Diagnostic criterion in ACR/EULAR 2010 classification; helps identify patients at risk for aggressive disease - **Timing:** Can appear years before symptom onset ### Comparison with Other Markers | Marker | Specificity | Sensitivity | Prognostic Value | |--------|-------------|-------------|------------------| | Anti-CCP | >95% | 60–70% | Predicts erosions, poor prognosis | | Rheumatoid Factor (RF) | 80–85% | 70–80% | Less specific; can be positive in other diseases | | ANA | Low for RA | N/A | Associated with SLE, not RA | | ESR/CRP | Non-specific | Variable | Reflects inflammation only | **High-Yield:** Anti-CCP positivity in seronegative (RF-negative) RA still indicates poor prognosis and need for aggressive DMARD therapy. **Clinical Pearl:** A patient with early RA who is anti-CCP positive but RF negative should still receive intensive DMARDs, as anti-CCP is more predictive of erosive disease than RF. [cite:Harrison 21e Ch 313]
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