Detection of Streptococcus pneumoniae and Haemophilus influenzae type b antigens in acute nonbacteremic pneumonia.

Commercially available latex agglutination and coagglutination reagents were evaluated for their ability to detect bacterial antigens in the sera of 165 patients to determine their suitability for rapid diagnosis of pneumonia. These reagents were used to detect the polysaccharide capsular antigens of Haemophilus influenzae type b and Streptococcus pneumoniae in nonbacteremic patients known to be respiratory culture positive for these organisms. The reagents were unable to detect the polysaccharide antigens in sera from nonbacteremic patients. Patients with a clinical diagnosis of pneumonia who had respiratory or extrarespiratory infections with a variety of organisms were also tested. No evidence of cross-reactivity or of false-positive reactions was observed with either reagent. Because a negative agglutination test may occur during the course of a nonbacteremic infection, these reagents should not be used alone, and if used, they should be used only in conjunction with standard bacteriological tests.