Anti-centromere antibodies explained

An antibody is a protein made by the immune system. Autoantibodies are antibodies that mistakenly target the body's own tissues. Lab Tests Online UK explains that ACA targets the centromere, part of the chromosomes found in the nucleus of cells, and that it is one of several autoantibodies that can be seen in the antinuclear antibody (ANA) test.

The ACA test is a blood test with a sample from a vein, and no preparation is needed. It is not offered by every laboratory and usually has to be sent to a reference laboratory.

The NHS describes scleroderma as a range of autoimmune conditions with hard, thickened areas of skin and sometimes problems with muscles, bones, internal organs and blood vessels. The two main types are localised scleroderma (morphoea) and systemic sclerosis, and systemic sclerosis is divided into limited cutaneous and diffuse forms.

The NHS says limited cutaneous systemic sclerosis usually affects the skin of the hands, lower arms, feet, lower legs and face, often starts as Raynaud's, and can eventually affect the lungs and digestive system. It tends to get gradually worse but is generally less severe than diffuse systemic sclerosis.

Lab Tests Online UK links the limited form to the CREST group of features: calcinosis (calcium deposits under the skin), Raynaud phenomenon, oesophageal dysfunction, sclerodactyly (tight, shiny skin on the fingers) and telangiectasia (small red spots). ACA is most associated with the limited cutaneous form.

• Calcinosis: calcium deposits under the skin.

• Raynaud phenomenon: fingers and toes turning white and blue in the cold.

• Oesophageal dysfunction: difficulty swallowing, acid reflux and heartburn.

• Sclerodactyly: tight, thick, shiny skin on the hands and fingers.

• Telangiectasia: red spots from swollen small blood vessels.

If ACA is positive and the person has symptoms of CREST, Lab Tests Online UK says it is likely they have limited cutaneous systemic sclerosis. The test may also help distinguish this from other conditions with similar symptoms.

If ACA is negative, the symptoms are likely due to another condition, although it is possible but rare to have limited cutaneous systemic sclerosis without ACA. A positive result without symptoms is harder to interpret, because ACA can be found in other autoimmune conditions and is not by itself a diagnosis.

ACA is not a measure of severity, and the sources used here do not describe it as a predictor of organ damage. A small hospital study of 108 people with systemic sclerosis in South Korea found anti-centromere antibodies were less common in those with interstitial lung disease (9.3% against 50.8% without), while anti-Scl-70 was more common, suggesting a different pattern of risk. The authors also noted that pulmonary hypertension was more frequent in those with lung disease. This is one single-centre study, so it is context rather than a rule.

The practical message is that organ checks, such as blood pressure, lung function tests and an assessment of swallowing, are decided by the rheumatology team on the basis of your symptoms, not on ACA alone. The NHS says people with scleroderma need regular blood pressure checks and other tests to check for problems with the organs.

If ACA is positive and your symptoms fit, a GP will usually refer you to a rheumatologist, who will examine your skin and fingers and arrange further tests. The Scleroderma and Raynaud's UK diagnosis page says systemic sclerosis often needs more tests than localised disease, including blood tests, checks of vital signs, sometimes a skin biopsy and lung function tests.

There is no cure for scleroderma, but the NHS says symptoms can usually be managed with a range of treatments, aimed at relieving symptoms, preventing the condition getting worse and detecting complications early. Lab Tests Online UK adds that ACA does not respond to lifestyle changes, so there is nothing to do to lower the level itself.