Meningitis antigen detection: interpretation of agglutination by ultrasound-enhanced latex immunoassay

Detailed instructions for performance and interpretation of ultrasound-enhanced latex agglutination tests for the rapid identification of bacteria causing meningitis are described. This recently developed technique, which enhances the sensitivity of most latex immunoagglutination assays, has been studied mainly in the context of detection of antigens of meningitis-causing bacteria. The test concentrates on the Wellcogen bacterial antigen kit (Murex Diagnostics Ltd) that contains five latex suspensions specific for Haemophilus influenzae type b, Neisseria meningitidis ACYW135, N. meningitidis B/Escherichia coli K1, Streptococcus group B and Streptococcus pneumoniae. Light photomicrographs of positive agglutination are shown. Particular attention is paid to the appearance of the latex in negative control samples following exposure to ultrasound. Guidance is given on interpretation and assessment in clinical samples.