Which antibody is most specific for systemic lupus erythematosus?

Which antibody is most specific for systemic lupus erythematosus?

• A. Anti-Smith (Sm)
• B. Anti-dsDNA
• C. Anti-RNP
• D. Anti-histone

Answer: (A)

Anti-Smith antibodies are highly specific for systemic lupus erythematosus. They target the Sm ribonucleoprotein complex and are found almost exclusively in SLE, so a positive test strongly supports the diagnosis. Other antibodies, like anti-dsDNA, are also associated with SLE but can appear in other conditions and are slightly less specific. Anti-RNP appears in various connective tissue diseases, and anti-histone is more typical of drug-induced lupus, making them less diagnostic for idiopathic SLE. So, the antibody most specific for SLE is Anti-Smith.

Anti-Smith antibodies are highly specific for systemic lupus erythematosus. They target the Sm ribonucleoprotein complex and are found almost exclusively in SLE, so a positive test strongly supports the diagnosis. Other antibodies, like anti-dsDNA, are also associated with SLE but can appear in other conditions and are slightly less specific. Anti-RNP appears in various connective tissue diseases, and anti-histone is more typical of drug-induced lupus, making them less diagnostic for idiopathic SLE. So, the antibody most specific for SLE is Anti-Smith.