Antibody tests for lupus

Antibody tests are a set of blood tests that check for specific antibodies to help clarify the diagnosis of lupus. They include:

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

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. However, 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.^{1, 2}
• High titers of anti-dsDNA are usually seen only in people with lupus.
• A positive anti-dsDNA suggests a higher risk of developing lupus-related kidney disease.
• A positive anti-Sm test is a specific marker for lupus and may be associated with more severe cases.

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

Citations

1. Lockshin MD (2005). Systemic lupus erythematosus. In DC Dale, DD Federman, eds., ACP Medicine, section 15, chap. 4. New York: WebMD.

2. Schur PH (2004). Systemic lupus erythematosus. In L Goldman, D Ausiello, eds., Cecil Textbook of Medicine, 22nd ed., vol. 2, pp. 1660–1670. Philadelphia: Saunders.