Comparison of three latex agglutination kits and counterimmunoelectrophoresis for the detection of bacterial antigens in a pediatric population.

Three commercial latex agglutination kits (Bactigen, Wampole Laboratories, Cranbury, NJ; Directigen, Hynson, Westcott & Dunning, Baltimore, MD; Wellcogen, Wellcome Diagnostics, Dartford, England) used for the detection of bacterial polysaccharide antigens (Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis) were compared with counterimmunoelectrophoresis and Gram stain for the identification of systemic bacterial disease in children. Urine and (when available) cerebrospinal fluid specimens were saved for all patients. Positive blood or cerebrospinal fluid culture isolates included 36 with H. influenzae type b, 11 with S. pneumoniae, 3 with N. meningitidis and 6 with other organisms. All latex kits performed similarly for the detection of H. influenzae type b antigen with a sensitivity range of 91 to 100%. The four methods performed poorly for the detection of S. pneumoniae (23 to 50%) and N. meningitidis (0%) antigen. Gram stain of cerebrospinal fluid appeared to be equally sensitive to the antigen detection methods for patients with meningitis. The false positive rates for the latex kits and counterimmunoelectrophoresis ranged from 2.8 to 9.2%, with Wellcogen having the lowest rates. The false negative rates ranged from 6.5% to 12% with Directigen having the lowest rate.