An evaluation of the role of laboratory investigations in establishing a diagnosis of central nervous system lupus.

By means of a questionnaire, we have determined the combination of clinical features and laboratory tests which rheumatologists, nephrologists, immunologists, and neurologists in New South Wales consider most helpful in discriminating between central nervous system (CNS) involvement due to systemic lupus erythematosus (SLE) and that due to other causes. There was a uniformity of views amongst the four specialties in terms of the likelihood that a given clinical presentation was due to active CNS lupus. The clinical presentation made little difference to the interpretation of laboratory data. CNS abnormalities (EEG, CT, and CSF), as well as the finding of serum DNA antibody of 95%, influenced decision-making, although the other serological tests had little impact. There was disagreement amongst physicians as to whether a given test abnormality (e.g. focal CT scan abnormality) supported or rejected the diagnosis of active CNS lupus. This study indicates that physicians interpret test results selectively in their assessment of patients with SLE who develop CNS symptoms.