Use and interpretation of rheumatologic tests: a guide for clinicians.

In recent years, several new autoantibody tests have been developed and are being used in the field of rheumatology, including the antineutrophil cytoplasmic antibody (ANCA) and myositis-specific antibodies such as anti-Jo1. Positive test results for ANCAs reveal one of two basic staining patterns: cytoplasmic (c-ANCA) or perinuclear (p-ANCA). The Jo1 antibody test is often helpful at the time of diagnosis of a new case of idiopathic inflammatory myopathy. Herein this article reviews the clinical utility of the new tests in conjunction with the established autoantibody tests including antinuclear antibodies and extractable nuclear antibodies. Both the antinuclear antibody and extractable nuclear antibody tests are helpful in diagnosing connective tissue diseases. Before the results of any of these tests can be interpreted, the physician must consider the sensitivity, specificity, and negative and positive predictive values. Positive results must be analyzed in the clinical context and in relationship to other autoantibody test results.