Detection of IgM antibodies to Neisseria meningitidis group A polysaccharide in meningitis patients by direct and antibody capture enzyme-linked immunosorbent assays.

Serum specimens obtained from culture-positive group A meningococcal meningitis patients in Cairo, Egypt were tested for immunoglobulin M (IgM) antibodies to Neisseria meningitidis group A polysaccharide by direct and IgM capture enzyme-linked immunosorbent assays (ELISAs). Sera from patients with meningitis caused by other bacteria were used as negative control specimens. The IgM antibodies to this antigen were detected by direct ELISA in 93% of 58 specimens obtained from patients with group A meningococcal disease three or more days after hospital admission, and by IgM capture ELISA in 83% of 60 such specimens. Sixteen percent of 25 specimens obtained three or more days after admission from negative control patients were positive by direct ELISA, and 4% were positive by IgM capture ELISA. The correlation coefficient of the results with the two assays was 0.85.