ANA Blood Test (Antinuclear Antibodies)

Antinuclear Antibodies (ANA) tests are designed to determine levels of antibodies in your blood and their patterns that work against the body (referred to as an autoimmune reaction). Antinuclear antibodies are associated with rheumatic diseases. This blood test is often used to identify immune system issues and autoimmune diseases like:

• Rheumatoid factor
• Polymyositis
• Sjögren's syndrome
• Scleroderma
• Systemic lupus erythematosus (SLE)

Overview

Antinuclear antibodies (ANA) consist of a diverse array of autoantibodies directed against multiple nuclear antigens (autoantigens) including deoxyribonucleic acid (DNA) and small ribonucleoproteins (snRNPs). ANA testing is useful in the diagnosis of systemic lupus erythematosus (SLE), systemic sclerosis (SSc), polymyositis (PM), dermatomyositis (DM), and Sjögren syndrome (SS). In addition, ANA testing is required for the diagnosis of drug-induced lupus, mixed connective tissue disease, and autoimmune hepatitis. The gold standard test for ANA is indirect immunofluorescence (FANA). ELISA testing is also available and while useful for high throughput testing, it affords less specificity.

ANA testing is an essential diagnostic tool in connective tissue and systemic rheumatic diseases; however, the antibodies are frequently associated with infectious and inflammatory conditions and can be found in as many as 30% of normal individuals. Because of this lack of specificity, the presence or absence of ANAs alone is not sufficient to confirm or refute a diagnosis. It is important to assess laboratory findings in the context of the clinical signs and symptoms. A number of autoantibody specificities have been identified while many remain uncharacterized. Some of these specificities have been directly associated with pathogenesis through the production of proinflammatory mediators while, for some specificities, the association with clinical symptoms is unclear. ANA testing is most useful in SLE and SS, diseases in which the presence of ANAs is high (>97%).

Clinical Significance

ANA testing is most useful as a diagnostic tool for the following conditions:

• Systemic lupus erythematosus (SLE)
• Systemic sclerosis (SSc)
• Polymyositis (PM)/dermatomyositis (DM)
• Sjögren syndrome (SS)

ANA testing is required for the diagnosis of the following conditions:

• Drug-induced lupus
• Mixed connective-tissue disease (MCTD)
• Autoimmune hepatitis

ANA testing may be useful in the prognosis of the following conditions:

• Juvenile idiopathic arthritis
• Antiphospholipid antibody syndrome
• Raynaud syndrome