Clinical utility of serum diagnostic tests for rheumatic diseases

Establishing a diagnosis of systemic rheumatic disease requires an integration of a patient's symptoms, radiological findings, and the result of biological tests. Clinicians often try to rely heavily on objective measures such as the presence of an autoantibody. Few tests are highly sensitive, though the antinuclear antibodies in systemic lupus erythematosus (SLE) and the erythrocyte sedimentation rate in polymyalgia rheumatica. Some tests are highly specific: anti-PR3 and anti-MPO among patients with Wegener granulomatosis (and related vasculitides), anti-ds DNA among patients with SLE and anti-CCP in rheumatoid arthritis. Medical literature may overestimate the diagnostic utility of many commonly ordered tests for rheumatic diseases. Serum rheumatologic tests are generally most usefull for confirming a clinically suspected diagnosis.