Rheumatic disease: How to use the laboratory in the workup

Tests for autoantibodies, particularly antinuclear antibodies (ANAs), are not, of themselves, diagnostic of connective tissue disease. Nevertheless, they may be useful adjuncts to clinical findings in identifying many of these disorders. Although a positive test for ANA is a strong indication of SLE, it may also indicate many other disorders. Thus, it may be helpful to follow up with further testing for more specialized ANAs that are specific for SLE, mixed connective tissue disease, Sjögren's syndrome, and other rheumatic conditions. In many cases, the extent of the antibody titer correlates directly with disease activity.