Radioimmunoassay of capsular polysaccharide antigens of groups A and C meningococci and Haemophilus influenzae type b in cerebrospinal fluid.

Sensitive radioimmunoassays capable of measuring 0-5 ng/ml of the Haemophilus influenzae type b polysaccharide and 2 ng/ml of the groups A and C meningococcal polysaccharides were developed and used to detect these substances in cerebrospinal fluid (CSF). Polysaccharide of the causative agent was detected in the CSF of 14 out of 15 patients with Haemophilus influenzae type b meningitis, in 18 out of 23 patients with group A, and in two out of four patients with group C meningococcal meningitis. In some cases the antigen could be detected even after three days of antibacterial treatment. No false positive reactions were seen. The assay procedure could be shortened to approximately three hours. These assays could be useful in routine diagnostic work and epidemiological investigations.