Laboratory investigation of systemic lupus erythematosus.

Diagnosis of systemic lupus erythematosus (SLE) requires documentation of multisystem involvement and the presence of antinuclear antibodies. In almost all cases of SLE, these autoantibodies are detected at significant titer with a sensitive screening test such as the fluorescent antinuclear antibody test. After other diagnostic possibilities, such as rheumatoid arthritis, have been excluded, several laboratory tests (hematocrit determination, complement tests, anti-native DNA assays) are available to monitor the response to therapy.