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Anti-SCL70 Antibodies

Immunology & Autoimmune

Anti-Topo IAnti-topoisomerase I antibodyScl-70Scl-70 antibody

Review status

Currently under review

Pending specialist review and validation.

What it shows

This test looks for antibodies in your blood that target an enzyme called DNA topoisomerase I, also known as Scl-70. These antibodies are a type of autoantibody, which means your immune system is reacting against one of your own proteins.

Anti-Scl-70 antibodies are most commonly associated with systemic sclerosis, an autoimmune connective tissue disease. The result is typically reported in relative units and is interpreted alongside other autoimmune tests and your clinical symptoms.

Why it matters

Finding anti-Scl-70 antibodies can help your clinician evaluate for systemic sclerosis and understand which organ systems might be at risk. This information may support earlier referral to a rheumatology specialist, closer monitoring, and targeted testing such as lung or heart assessments when appropriate.

The test is often ordered when there are features such as Raynaud symptoms, skin thickening, digital ulcers, swallowing difficulty, or shortness of breath. It may be part of a broader autoantibody panel to clarify a suspected autoimmune condition and to help differentiate systemic sclerosis from other rheumatic diseases.

Understanding your results

A positive result supports the diagnosis of an autoimmune connective tissue disease, particularly systemic sclerosis, but it is not the only piece of information your care team will use. Some people with systemic sclerosis do not have this antibody, and rarely it can appear in other conditions, so your symptoms, examination, and other tests still guide decisions.

A negative result lowers the chance of this specific antibody being present, but it does not rule out systemic sclerosis or other autoimmune diseases. Your clinician may combine this result with other markers, imaging, or lung and heart evaluations. If results are unclear or unexpected, repeat testing or confirmation with a different method may be considered, and a rheumatology consultation may be recommended.

Reference ranges

0 – 19 RU/mL
All sexes
0 days – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Anti-SCL70 Antibodies

  • Disease activity and timing

    Autoantibody levels can vary over time and may not directly track with how active your symptoms are. A single result is best interpreted in the context of your current clinical picture and follow-up testing.

  • Medications and therapies

    Immunosuppressive drugs, biologics, or recent intravenous immunoglobulin can influence autoantibody testing. Tell your care team about all medicines and recent treatments when your blood was drawn.

  • Testing method differences

    Laboratories may use different assay methods or manufacturers. Results from different labs are not always interchangeable, so your clinician may prefer follow-up testing at the same laboratory.

  • Coexisting autoimmune conditions

    Other autoimmune diseases can affect the overall autoantibody profile and how your result is interpreted. Your clinician will consider the full antibody panel and your symptoms together.

  • Sample handling and timing

    Improper sample handling or delays in processing can rarely affect immunoassay performance. If a result does not fit your clinical situation, repeat testing may be requested.

  • Pregnancy and special populations

    Pregnancy and certain infections can complicate interpretation of autoantibody tests. Clinical context and specialist input are important to avoid overdiagnosis or missed diagnoses.

2026

References

  1. McGill University Health Centre. (2009, September 21). Anti-SCL70 Antibodies (Task CD 699283). Laboratory reference ranges.
  2. van den Hoogen, F., Khanna, D., Fransen, J., Johnson, S. R., Baron, M., Tyndall, A., ... & Pope, J. E. (2013). 2013 classification criteria for systemic sclerosis: An American College of Rheumatology/European League Against Rheumatism collaborative initiative. Arthritis & Rheumatism, 65(11), 2737–2747.
  3. Kowal-Bielecka, O., Fransen, J., Avouac, J., Becker, M., Kulak, A., Allanore, Y., ... & EUSTAR Co-authors. (2017). Update of EULAR recommendations for the treatment of systemic sclerosis. Annals of the Rheumatic Diseases, 76(8), 1327–1339.