Newer laboratory parameters for the diagnosis of rheumatic disease.

Measurement of serum autoantibodies is a useful adjunct in the diagnosis of connective tissue diseases. Approximately 15 percent of patients with rheumatoid arthritis are seronegative for rheumatoid factor by standard assays. The development of enzyme-linked immunosorbent assays for additional isotypic and idiotypic determinants may expand the diagnostic sensitivity of rheumatoid factor measurements. Although extremely sensitive, the finding of antinuclear antibodies is not highly specific for systemic lupus erythematosus and related disorders; the ability to rapidly screen serum against newly characterized specific nuclear antigens has been helpful in the diagnosis of newly described systemic lupus erythematosus subtypes, overlap syndromes, Sjögren's syndrome, and scleroderma variants. Women with unexplained recurrent fetal loss and patients with unexplained thrombotic episodes should be screened for the presence of the anticardiolipin antibody. Glycoproteins (C-reactive protein, alpha-1-glycoprotein, fibronectin) may prove useful as indicators of rheumatic disease activity and the efficacy of therapeutic intervention.