ANTI-SSA ANTIBODIES

CLINICAL UTILITY:

Antibodies to the SSA antigen (also known as Ro antigen), appear in 60-70% of patients with primary Sjogren's syndrome (SS), in 30-40% of patients with SLE, in other connective tissue diseases, and in babies with neonatal lupus erythematosus. On rodent tissue, the substrate traditionally used for ANA testing, the SSA (Ro) antigen is predominantly cytoplasmic, and not located in the nucleus. Therefore, patients with antibody to SSA may be ANA negative on routine testing. These ANA negative patients represent about 1–5% of SLE cases. Approximately 62% of ANA negative lupus patients have antibodies to SSA, and frequently have subacute cutaneous lupus erythematosus, a variant of SLE characterized by subacute or chronic photosensitive rashes.

Another disease associated with anti-SSA antibodies is neonatal lupus, a condition found occasionally in the infants of mothers with SLE. In rare instances neonatal lupus is manifest as congenital heart block. Transplacental passage of maternal antibodies seems to lead to the transient photosensitive rash or the congenital heart block in these infants.

METHOD DESCRIPTION:

Double diffusion and CIE are the methods used to identify anti-SSA antibodies. Human spleen extract containing the SSA antigen reacts with patient sera, causing precipitin lines to occur if antigen-antibody complexes form. Results are reported as positive or negative.

REFERENCE RANGE:

Negative.

SPECIMEN REQUIREMENTS:

0.5 mL serum. Freeze.