Antibodies to Sm and SS-A demonstrated by enzyme immunoassay. Correlation to clinical manifestations and disease activity in patients with systemic lupus erythematosus.

Using commercially available antigens, enzyme-linked immunosorbent assays (ELISAs) were set up to demonstrate antibodies of IgG class against Sm and SS-A. Anti-Sm antibodies were demonstrated in 40% of patients with systemic lupus erythematosus (SLE), in 12% of patients with SJögren's syndrome, in 6% of patients with rheumatoid arthritis (RA) and in 12% of patients with miscellaneous rheumatic disorders. Anti-SS-A antibodies were seen in 63% of the SLE patients, in 37% of the patients with Sjögren's syndrome and in 23% of the patients with RA. In the patients with SLE, high levels of anti-Sm antibodies were related to the presence of Raynaud's phenomenon, whereas patients with a malar rash tended to have high levels of anti-SS-A antibodies. In 17 SLE patients followed over a period of time a correlation was seen between the levels of the anti-Sm antibodies and the disease activity. We concluded that it is useful to include ELISAs for the demonstration of anti-Sm and anti-SS-A antibodies in determining the serological profile and in the follow-up of patients with SLE.