Which autoantibody is commonly used for the diagnosis of lupus and is reported in titers such as 1:80 or higher?

• A. dsDNA
• B. RF
• C. Anti-CCP
• D. ANA

Answer: (D)

In lupus diagnosis, a screening test that is widely used is the antinuclear antibody (ANA) test because it’s highly sensitive for systemic lupus erythematosus. ANA detects autoantibodies directed against components in the cell nucleus. The result is a titer, such as 1:80 or higher, which indicates the concentration of those antibodies. A positive ANA makes lupus likely enough to pursue further testing, but it’s not specific to lupus—ANA can be positive in many other autoimmune diseases and even in healthy individuals, especially with age or concurrent infections. So while a positive ANA is a helpful first clue, diagnosis relies on the overall clinical picture plus more specific antibodies when needed.

More specific tests, like antibodies to double-stranded DNA (dsDNA), are especially useful for confirming lupus in the right clinical context and can correlate with disease activity, notably nephritis, but they are not used as broad screening tests. RF and anti-CCP are associated with rheumatoid arthritis, not lupus, so they aren’t the primary tests for diagnosing SLE.