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Anti-Citrullinated Protein Antibody (ACPA)
Related Subjects: |Ferritin |CEA |ESR |CRP |ALP |LDH |HbA1c |Alpha Fetoprotein |Anti-Hu ab |Anti-Yo ab |Anti-SCL70 ab |Biochemical Lab values
🧪 Anti-Citrullinated Protein Antibodies (ACPAs): These autoantibodies often precede the onset of clinical rheumatoid arthritis (RA) and are associated with more aggressive disease. They are highly useful as both diagnostic and prognostic tools.
ℹ️ About
- ⏳ Turnaround time for results may be several weeks.
- 🔬 ACPAs (anti-CCP antibodies) are detected using laboratory assays.
🧬 Aetiology
- 🔄 In >90% of RA patients, the immune system produces autoantibodies against citrullinated proteins (arginine → citrulline modification).
- 🧠 This immune response may drive the inflammation seen in RA, as citrullinated proteins and the enzymes generating them are abundant in inflamed synovium.
- 🧪 Anti-CCP assays use synthetic cyclic citrullinated peptides and are both more sensitive and more specific than rheumatoid factor (RF).
- 📊 NICE (2009) still recommends RF as a first-line test (cost-effectiveness), but anti-CCP is superior diagnostically.
- ⚠️ A positive anti-CCP in adults is highly predictive of RA and may appear years before clinical symptoms.
- 🔍 A minority of RA patients remain anti-CCP negative, though newer assays continue to reduce this group.
Clinical Use
- 👩⚕️ Used in patients with suspected rheumatoid arthritis, especially when RF is negative or diagnosis is uncertain.
- 📉 Positive anti-CCP predicts more severe erosive disease and worse long-term outcomes.
🔎 Investigations
- 💡 Assay: Fluorescence enzyme-linked immunoassay (FEIA, e.g. Phadia ImmunoCAP 250).
- 🧾 Reference ranges:
- ❌ Negative = < 7 U/mL
- ⚖️ Equivocal = 7–10 U/mL
- ✅ Positive = > 10 U/mL
- 📈 Assay detection range: 0.4 to > 340 U/mL.
References
- 📖 NICE Clinical Knowledge Summaries: Rheumatoid Arthritis
- 📚 NCBI – Anti-CCP and RA diagnosis
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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