Comparison of counter-current immunoelectrophoresis, latex agglutination, and radioimmunoassay in detection of soluble capsular polysaccharide antigens of Haemophilus influenzae type b and Neisseria meningitidis of groups A or C.

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Abstract
Three serological methods, radioimmunoassay (RIA), latex agglutination (LX) and counter-current immunoelectrophoresis (CIEP), for sensitivity in the detection of the capsular polysaccharide antigen [Ag] of H. influenzae type b or N. meningitidis groups A and C were compared. RIA was consistently the most sensitive, LX the next and CIEP the least sensitive. When RIA and LX were used to test CSF samples of patients with meningitis, they gave very similar results. In 2 of 47 samples, in which RIA detected 1 of the 3 Ag, the amount of the specific polysaccharide was too low to be detected by LX. By the serological methods evidence of specific pathogen was detected in 49 samples, including 9 from patients who had received intensive anti-microbial treatment for up to 3 days and from whom specimens yielded no bacteria on culture. The reactions were specific in all cases except 2 out of 47 tests positive by LX. From these 2 CSF samples N. meningitidis group B could be cultivated, whereas the LX was recorded positive for N. meningitidis of group A in 1 case, and of group C in the other. The nonspecific reactions could be due to antibodies to bacterial components other than the capsular polysaccharide.