Rapid diagnosis of Hemophilus influenzae type b infections by latex particle agglutination and counterimmunoelectrophoresis.

Latex particle agglutination and counterimmunoelectrophoresis techniques were compared in a clinical trial to demonstrate their sensitivity, specificity, and usefulness in the rapid diagnosis of invasive Hemophilus influenzae type b disease. LPA, a simplified LPA performed by house officers, and CIE used in this study detected 0.2, 0.5, and 1 to 10 ng/ml of Hib capsular antigen, respectively. One hundred-six illnesses suspected of being caused by Hib were evaluated prospectively by these assays. A total of 39 of these were confirmed by culture or detection of antigen or both. LPA and simplified LPA were more sensitive and specific than CIE in the diagnosis of Hib disease (P less than 0.01), especially in invasive disease other than meningitis. LPA is inexpensive, can be performed quickly, and detects all invasive Hib infections. The results emphasize the usefulness of antigen detection in the rapid diagnosis of Hib infections, demonstrate that LPA is more sensitive and specific than CIE, and can be conveniently performed by physicians.