What is Centromere Antibodies?
Also Known As: Centromere Antibody, ACA
The anticentromere antibody (ACA) is an autoantibody, a protein produced by the immune system that mistakenly targets the body’s own tissues. ACA is one of several antinuclear antibodies. It targets the centromere, a component of the chromosomes (structures in the nucleus) found in all nucleated cells in our bodies except red blood cells. The ACA test detects and measures the amount of anticentromere antibody found in blood to help diagnose a form of scleroderma.
Scleroderma (also known as systemic sclerosis) is a group of rare connective tissue disorders. (For more details, see the condition article on Scleroderma.) There are two distinct subtypes of systemic sclerosis that are defined based on how much of the skin is affected:
- Diffuse cutaneous systemic sclerosis that affects the entire body
- Limited cutaneous systemic sclerosis is typically associated with one or more symptoms that are known collectively as CREST syndrome
CREST syndrome symptoms include:
- Calcinosis – calcium deposits under the skin
- Raynaud phenomenon – episodes of decreased blood flow to fingers and toes, causing them to turn white and blue
- Esophageal dysfunction – difficulty swallowing, acid reflux, and heartburn
- Sclerodactyly – tight, thick, shiny skin on the hands and fingers
- Telangiectasia – red spots on skin due to swollen capillaries
Other signs that may be considered in scleroderma include fingertip lesions, abnormal capillaries in the skin just below the fingernails, high blood pressure in the lungs (pulmonary arterial hypertension), and/or scarring of the lungs (interstitial lung disease).
ACA is found in about 60-80% of people who have limited cutaneous scleroderma while only about 5% of patients with diffuse scleroderma have ACA. ACA can be present in up to 95% of people who have CREST syndrome.
How is the test used?
The anticentromere antibody (ACA) test is primarily ordered to help diagnose the autoimmune disorder limited cutaneous scleroderma, a form of systemic scleroderma, and CREST syndrome. The test may be used to distinguish between this and other conditions with similar symptoms.
An ACA test may be ordered along with other tests for autoantibodies, including ANA (antinuclear antibody) testing. ACA testing may be used to provide your healthcare practitioner with additional information if an ANA test is positive, especially if the test produces a certain pattern characteristic of particular antibodies. (For more on this, see the “What does the test result mean?” section in the ANA article.)
An ACA test may be ordered along with an Scl-70 (anti-topoisomerase I) test. Scl-70 is another autoantibody that may be present with scleroderma. An anti-RNA polymerase III autoantibody (ARA) test may also be ordered in the diagnosis of systemic sclerosis. These autoimmune antibody tests could be performed as part of an Extractable Nuclear Antigen (ENA) antibody panel or other antibody panels for autoimmune disorders and/or systemic sclerosis.
