Anti-Centromere Antibody (ACA) Test

The Anti-Centromere Antibody (ACA) Test detects antibodies that target centromere proteins, which are associated with certain autoimmune diseases, particularly limited systemic sclerosis (CREST syndrome).

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Why is the Anti-Centromere Antibody (ACA) Test Done?

✅ To Diagnose Systemic Sclerosis (Scleroderma)

• Limited Cutaneous Systemic Sclerosis (CREST Syndrome) – Most commonly linked to ACA-positive results.
• Diffuse Systemic Sclerosis – ACA may be present but less common.

✅ To Differentiate Between Autoimmune Diseases

• Helps distinguish CREST syndrome from other connective tissue diseases like lupus (SLE), rheumatoid arthritis (RA), or Sjögren’s syndrome.

✅ To Assess Risk of Pulmonary Hypertension & Other Complications

• ACA-positive patients may develop pulmonary artery hypertension (PAH), esophageal dysfunction, or Raynaud’s phenomenon.

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Test Procedure

🩸 Blood Sample Collection:

• A blood sample is drawn from a vein.
• No fasting required.
• Results available in 3–7 days.

🔬 Methods Used:

• Indirect Immunofluorescence Assay (IFA) – Uses HEp-2 cells to detect centromere pattern.
• Enzyme-Linked Immunosorbent Assay (ELISA) – Measures ACA levels.
• Line Immunoassay (LIA) – Confirms ACA presence.

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Normal Range & Interpretation

🔹 ACA can be present years before symptoms appear.
🔹 A positive test alone does NOT confirm disease—clinical evaluation is necessary.

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What Do Abnormal ACA Test Results Mean?

🔴 High ACA Levels Suggest:

• Limited Systemic Sclerosis (CREST Syndrome) – Most common association (60–80% of cases).

  • Calcinosis – Calcium deposits under the skin.
  • Raynaud’s phenomenon – Blood flow problems in fingers/toes.
  • Esophageal dysmotility – Swallowing difficulty.
  • Sclerodactyly – Skin thickening of fingers/hands.
  • Telangiectasia – Dilated small blood vessels on the skin.

• Primary Biliary Cholangitis (PBC) – ACA is found in 10–30% of cases, a liver autoimmune disease.

• Pulmonary Hypertension – ACA-positive individuals have a higher risk of developing PAH.

• Overlap Syndrome (Mixed Connective Tissue Disease – MCTD) – ACA can be mildly elevated.

🟢 Negative ACA:

• Systemic sclerosis is unlikely, but other autoimmune diseases may still be present.

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Next Steps If ACA Is Positive?

🔬 Additional Tests for Confirmation:

• ANA (Antinuclear Antibody Test) – ACA is a specific ANA pattern (centromere staining).
• Anti-Scl-70 Antibody Test – Helps distinguish diffuse systemic sclerosis.
• Pulmonary Function Tests & Echocardiogram – Checks for lung or heart involvement.
• Liver Function Tests (LFTs) & Anti-Mitochondrial Antibodies (AMA) – If primary biliary cholangitis (PBC) is suspected.

✅ Treatment Options If Positive:

• CREST Syndrome: Symptom management with vasodilators, immunosuppressants, and skin treatments.
• Pulmonary Hypertension Risk: Regular heart & lung monitoring with specialists.
• Primary Biliary Cholangitis: Ursodeoxycholic acid (UDCA) for liver disease.

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Key Takeaways

🔹 ACA is strongly linked to CREST syndrome (limited systemic sclerosis).
🔹 Test helps differentiate between autoimmune diseases like scleroderma, lupus, and PBC.
🔹 A positive test suggests increased risk of pulmonary hypertension and esophageal dysfunction.
🔹 Clinical correlation and additional tests are needed for diagnosis.