Anti-Scl-70 Ab (RDL)

The Anti-Scl-70 (anti–topoisomerase I) antibody test supports the diagnosis of systemic sclerosis and helps distinguish scleroderma from other systemic autoimmune connective tissue diseases in the context of ANA-specific and ENA antibody testing. Results can clarify the significance of a positive ANA and guide evaluation when clinical features suggest systemic autoimmunity. Anti-Scl-70 antibodies are reported in approximately 20% of patients with scleroderma, with frequencies varying by clinical subtype and population. These antibodies may also occur in overlap syndromes, either alone or together with other autoantibody specificities.

Antibodies to extractable nuclear antigens target soluble nuclear ribonucleoprotein components. Among these, IgG to DNA topoisomerase I (Scl-70) demonstrates high specificity for systemic sclerosis. Positivity is more often linked to diffuse cutaneous involvement and is associated with an increased risk of interstitial lung disease. Autoantibody specificities can appear in isolation or coexist with other antibodies in overlap syndromes.