What does the Anti-Scl-70 (Topoisomerase I) Antibody test measure?

Why is Anti-Scl-70 (Topoisomerase I) Antibody measured?

Anti-Scl-70 is the serological hallmark of diffuse cutaneous systemic sclerosis (dcSSc) and carries strong prognostic significance — positive patients have substantially elevated risk of pulmonary fibrosis and interstitial lung disease. It is rarely co-positive with anti-centromere B, with the two antibodies largely defining divergent SSc disease subsets.

Reference ranges

Standard reference

<1.0 AI (negative); ≥1.0 AI (positive) # REVIEWER FLAG: Confirm cut-off and reporting format with Access Med Labs.

Functional medicine optimal

Negative — positive result in a patient with skin thickening, Raynaud's, or unexplained dyspnoea mandates urgent assessment for systemic sclerosis and proactive ILD screening.

Units

AI (antibody index)

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.