What are Smith Antibodies? High and low values | Lab results explained

AKA: Anti-Smith Antibody / Sm / Anti-Sm antibodies / Smith (ENA) Antibody, IgG

The Anti-Smith antibody targets your body’s own proteins and is found almost exclusively in people with lupus. Though not all people with lupus have this antibody (only around 30%), those who do usually receive a diagnosis of lupus. Anti-Smith antibody is more common in blacks and Asians with SLE (around 60%) than in whites with SLE.

• It is occasional also present in mixed connective-tissue disease (MCTD).
• Anti-Smith antibody levels are elevated in 30% of SLE cases and 8% of MCTD cases
• They almost never occur in healthy individuals or patients with other diseases.
• High levels persist even after anti-DNA levels have returned to the normal range. This is useful when testing a patient with decreased signs or symptoms of SLE.

High levels:

Though not all people with lupus have this antibody, those who do usually receive a diagnosis of lupus.

References:

– What is the clinical significance of anti-Sm antibodies in systemic lupus erythematosus? A comparison with anti-dsDNA antibodies and C3. [L]