Limulus assay for bacterial endotoxin in synovial fluid.

The limulus assay for the detection of bacterial endotoxin has been applied to the study of synovial fluid. Three of 5 patients (60%) with culture-positive gonococcal arthritis had positive SF limulus assay results; as did 2 of 11 (18%) with presumptive evidence of gonococcal arthritis, 3 of 6 (50%) with nongonococcal infectious arthritis, and none of 47 patients with noninfectious arthritis. Endotoxin levels ranged from 0.25 to 128.0 ng/ml. As at present applied to synovial fluid the commercial limulus assay appears to be specific for the infectious process but apparently lacks sensitivity.