Extractable Nuclear Antigen (ENA) panel

Screening for anti-ENA antibodies is used to investigate patients with connective tissue autoimmune symptoms and signs and in whom antinuclear antibodies (ANA) are positive.

Antibodies against Extractable Nuclear Antigen (ENA) or anti-ENA are used to diagnose systemic lupus erythematosus (SLE) and mixed connective tissue disease and to exclude other autoimmune diseases. Anti-ENAs are a type of antinuclear antibody against certain core antigens consisting of RNA and proteins. The most common ENA antigens are Smith (SM) and ribonucleoprotein (RNP). The ENA antigens also include SS-A (Ro), SS-B (La), Jo-1, and Scl-70.

Antinuclear Smith (anti-Smith, anti-SM) are found in about 30% of patients with systemic lupus erythematosus and in about 8% of patients with mixed connective tissue disease. However, they are not found in patients with other collagen diseases.

Antinuclear antibodies against ribonucleoprotein (anti-RNP) are found in approximately 100% of patients with mixed connective tissue disease and in approximately 25% of patients with systemic lupus erythematosus, discoid lupus, and progressive systemic sclerosis (scleroderma). High anti-RNP titers indicate mixed connective tissue disease.

Antibodies against histidyl tRNA synthetase (Anti-Jo-1) are found in patients with autoimmune interstitial pulmonary fibrosis and in a few patients with autoimmune myositis.

Anti-SS-A (Ro) and anti-SS-B (La) antibodies are mainly used in the diagnostic evaluation of Sjögren’s syndrome.

Scleroderma antibodies (anti-Scl-70) are found in patients with scleroderma and CREST syndrome.