Anti-Scl-70 antibodies explained

Anti-Scl-70 is one of several antibodies in the extractable nuclear antigen (ENA) group, antibodies that react with proteins in the cell nucleus. Lab Tests Online UK explains that autoantibodies are produced when the immune system mistakenly targets the body's own tissues, and that certain autoimmune disorders are characteristically associated with particular anti-ENA antibodies, which can help diagnose and distinguish between them.

An ENA panel typically has 4 or 6 tests, depending on the laboratory. The 4-test panel (anti-RNP, anti-Sm, anti-SS-A and anti-SS-B) helps diagnose mixed connective tissue disease, lupus and Sjögren syndrome. The 6-test panel adds Scl-70 and anti-Jo-1, and can help identify scleroderma and polymyositis or dermatomyositis. The tests require specialised laboratory equipment and cannot be done in a GP surgery.

Lab Tests Online UK states that a positive Scl-70 is seen in about 60% of people with scleroderma and is a highly specific antibody marker for this disease. When symptoms suggest scleroderma and the corresponding antibody is positive, it is likely that the person has that condition.

The NHS describes two types of systemic sclerosis: limited cutaneous, and diffuse, which causes skin changes that can affect the whole body and is more likely to affect internal organs. Lab Tests Online UK ties anti-centromere antibodies mainly to the limited form and reports them in only about 5% of diffuse disease, so a different antibody such as Scl-70 may be found instead. Neither antibody on its own settles the diagnosis, which depends on your symptoms, examination and other tests.

The NHS says that in some cases of systemic sclerosis, organs such as the heart, lungs or kidneys are affected, which can cause shortness of breath, high blood pressure and pulmonary hypertension. Scleroderma and Raynaud's UK explains that internal organ tissue in the lungs can become thicker and stiffer, making breathing harder.

Research supports an association between Scl-70 and interstitial lung disease (ILD). In the 2018 Archives of Rheumatology study of 108 patients with systemic sclerosis, positive anti-Scl-70 was seen in 62.8% of those with ILD against 15.4% of those without, while anti-centromere antibodies were seen in 9.3% against 50.8%. Positive anti-Scl-70 was independently associated with ILD, with an odds ratio of about 15.7, alongside platelet count, ESR and pulmonary hypertension.

This was a single-centre retrospective study in South Korea, and many people with lung involvement do not carry the antibody. The practical consequence is that a positive result prompts attention to the lungs, but a negative result does not remove the need to check them if you have symptoms such as breathlessness or a persistent dry cough.

The table summarises how the two antibodies are described in the sources used for this page.

After a positive Scl-70 with compatible symptoms, referral is to a rheumatologist. Scleroderma and Raynaud's UK says systemic sclerosis often needs more tests, including blood tests, checks of blood pressure and breathing rate, a skin biopsy and a lung function test, with imaging in some people. The specialist will decide whether you need a chest scan and how often to repeat lung function tests.

Treatment is aimed at relieving symptoms, preventing the condition getting worse and detecting and treating complications, according to the NHS. It includes medicines to improve circulation and medicines that reduce immune activity. It cannot be cured, but many symptoms can be managed.

If you have noticed new shortness of breath, a persistent dry cough, swallowing problems or finger ulcers, mention them to your clinician early rather than waiting for the next scheduled check.