Latex agglutination test for screening of Haemophilus influenzae type b carriers.

Latex agglutination (LA) for the demonstration of Haemophilus influenzae type b capsular antigen in nasopharyngeal swabs was applied to the screening of H. influenzae type b carriers and compared with culturing by the antiserum agar method on Levinthal-bacitracin plates. Altogether, 51 (33%) of the 154 nasopharyngeal specimens collected from the close contacts of patients with invasive H. influenzae type b disease were positive in LA or the antiserum agar method or both. All 40 culture-positive samples were also positive in LA, and in 11 (9.6%) culture-negative samples, H. influenzae type b antigen was demonstrated by LA. LA as used in the present study is cheap, rapid, and easy to perform and is thus an ideal tool for the screening of H. influenzae type b carriers.