Detection of meningitis antigens in buffer and body fluids by ultrasound-enhanced particle agglutination.

The standard test card agglutination of antibody-coated latex by Neisseria meningitidis. Streptococcus group B, Haemophilus influenzae type b and Streptococcus pneumoniae antigens has been compared with a technique involving local concentration of the coated latex in an ultrasonic standing wave. The detection of positive control antigen was enhanced, compared with the test-card procedure, over a 16 to 64 fold range on exposure to ultrasound. Sample filtration eliminated non-specific agglutination on ultrasonic exposure of latex in control serum, urine or concentrated urine. Tests of meningitis patient body fluids showed increased detection of antigen with ultrasound for CSF (11/14 > 7/14) serum (8/13 > 3/13) and concentrated urine (8/17 > 2/17) compared to test card assays. The ultrasound detection of antigen in serum or concentrated urine was comparable to that achieved with CSF on test cards. Serum dilution experiments showed that ultrasound could detect antigen in serum over a 1000 fold concentration range.