Appropriate laboratory testing in rheumatic diseases.

The diagnosis and management of systemic rheumatic disease is predominantly based on clinical parameters. Nevertheless, specific laboratory diagnostic tests may often be critically helpful, for example, in ruling out septic and crystal-induced arthritis in the differential diagnosis of acute monoarthritis. In the evaluation of patients with polyarticular rheumatic disease syndromes, autoimmune testing may be helpful to corroborate the clinical diagnosis of such diverse illnesses as rheumatoid arthritis, systemic lupus erythematosus, Lyme disease, and anticardiolipin syndrome.