Lupus is a tricky disease to diagnosis because its signs and symptoms mimic those of so many other diseases. When diagnosing the disease, doctors take in many factors, including a patient’s medical history, routine lab test results, and specialized tests focused on immune status.
A common test that is often performed is the anti-nuclear antibody (ANA) blood test, which screens for several autoimmune diseases by determining whether autoantibodies to cell nuclei are present in a person’s bloodstream.
If the ANA test comes back positive, and the patients is showing signs and symptoms common to lupus, the doctor may order a number of follow-up tests to detect specific autoantibodies, including an anti-DNA test, an anti-SM test and an anti-RNP.
The anti-DNA test is one of several blood tests that specifically detect individual types of autoantibodies, many that are specific to people with lupus. Not that not all people with lupus have the same antibodies. These antibodies include anti-DNA antibodies, which attack a person’s DNA.
Similarly, anti-Sm autoantibodies are almost exclusively found in lupus patients, and antibodies to ribonucleoprotein (RNP) are an indicator of mixed connective tissue disease, a condition with symptoms like SLE.
Sources:
Handout on Health: Systemic Lupus Erythematosus. National Institute of Arthritis and Musculoskeletal and Skin Diseases. August 2003.
Laboratory Tests. Lupus Foundation of America. January 2008.
