Anti-Centromere Antibody (ACA) Test: Overview

The Anti-Centromere Antibody (ACA) test detects autoantibodies targeting centromere proteins in the nucleus of cells. It is primarily used to diagnose and differentiate systemic sclerosis (scleroderma) and other autoimmune diseases.

Purpose of the Test

✅ Diagnosing limited cutaneous systemic sclerosis (lcSSc), also known as CREST syndrome
✅ Differentiating systemic sclerosis subtypes (limited vs. diffuse)
✅ Evaluating Raynaud’s phenomenon and other autoimmune conditions

Interpreting Results

🔹 High ACA titers are found in 60-80% of patients with limited systemic sclerosis (CREST syndrome).
🔹 Rarely seen in diffuse systemic sclerosis, where anti-Scl-70 (topoisomerase I) antibodies are more common.

Clinical Significance

• Limited Cutaneous Systemic Sclerosis (CREST Syndrome) → Characterized by Calcinosis, Raynaud’s phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia.

• Raynaud’s Phenomenon → ACA is present in 30-50% of Raynaud’s cases, especially when it progresses to systemic sclerosis.

• Primary Biliary Cholangitis (PBC) → ACA is sometimes positive in PBC, another autoimmune disease affecting the liver.

Additional Autoimmune Tests

✔ ANA (Antinuclear Antibody Test) → Often positive in systemic sclerosis.
✔ Anti-Scl-70 (Topoisomerase I Antibody) → More common in diffuse systemic sclerosis (dcSSc).
✔ Anti-RNA Polymerase III Antibody → Associated with rapidly progressing systemic sclerosis.
✔ Anti-Phospholipid Antibodies → Evaluates clotting risks in autoimmune diseases.
✔ Pulmonary Function Tests & Echocardiogram → To monitor lung and heart complications in systemic sclerosis.

Next Steps if Positive

🔹 Evaluate symptoms (Raynaud’s, skin tightening, swallowing issues, lung involvement).
🔹 Consider additional autoimmune tests to confirm the diagnosis.
🔹 Regular follow-ups with a rheumatologist for systemic sclerosis monitoring.