Overview

Antibody tests are a set of blood tests that check for specific antibodies to help clarify the diagnosis of lupus. They may also be called an ENA (extractable nuclear antibody) screen. They include:

• Anti-dsDNA (antibodies to DNA).
• Antinuclear antibody (ANA)
• Anti-RNP.
• Anti-Smith (Sm).
• Anti-SS-A (also called Ro).
• Anti-SS-B (also called La).

These antibody tests are often positive in lupus and can provide support for a diagnosis if the clinical criteria are unclear or if the ANA test is negative but lupus is strongly suspected.

• Anti-SS-A (Ro) and anti-SS-B (La) antibodies are not specific for lupus and are found commonly in Sjögren's syndrome. But these tests are useful in helping women with lupus who are considering pregnancy. If a woman who has these antibodies becomes pregnant, she may need more careful monitoring of the fetus, since these antibodies are associated with a higher risk of the baby being born with neonatal lupus syndrome or a heart defect called congenital heart block.
• High titres of anti-dsDNA are usually seen only in people who have lupus.
• A positive anti-Sm test is a specific marker for lupus.

Anti-dsDNA tests can be repeated at intervals to monitor how the disease is progressing.