Use of a latex agglutination test in rapid diagnosis of acute meningitis.

Capsular antigens of Neisseria meningitidis groups A, B, C, Y and W135, Streptococcus pneumoniae and Haemophilus influenzae were searched in CSF specimens of 66 patients with acute meningitis, using a latex agglutination test. Simultaneously CSF samples were processed for Gram stain and culture. Blood cultures were also performed in all patients. The test was positive in 43 (82.7%) samples: N. meningitidis-19, S. pneumoniae-18 and H. influenzae-6. In 32 samples the result of the test was concordant with CSF or blood culture. In 11 cases the test was positive but CSF or blood cultures were negative. Gram stain was diagnostic in 13 (25%) samples in which the latex agglutination test was also positive, and were negative in the remaining cases. There were six false negative tests. In 17 cases the test, culture and Gram stain were simultaneously negative: 14 cases corresponded to viral meningitis, and the three other were unidentified purulent meningitis. Concluding, the test was useful in early aetiologic diagnosis of acute meningitis, but the occurrence of false negative results requires a complete bacteriological study.