Cerebrospinal fluid (CSF) and joint fluid from 81 patients were studied for the presence of endotoxin using the limulus assay. All fluids that grew Gram-negative organisms had a positive limulus test. However, one sample of CSF and one of joint fluid, both very purulent, that contained Gram-positive organisms also gave positive limulus assays. All culturally negative fluids had a negative limulus assay. Thus, a positive limulus assay with CSF or joint fluid is indicative of bacterial infection probably caused by Gram-negative organisms and can be an extremely useful diagnostic adjunct.
(Arch Intern Med 137:55-56, 1977)