Rapid diagnosis of community-acquired bacterial pneumonia

Rapid identification of pathogens in patients with bacterial pneumonia is important for optimal antimicrobial therapy. Coagglutination was compared with counterimmunoelectrophoresis (CIE) for sensitivity and specificity in the detection of Streptococcus pneumoniae, Hemophilus influenzae, Klebsiella pneumoniae, and Pseudomonas aeruginosa antigens in sputum specimens of 101 patients with community-acquired pneumonia. Coagglutination detected the appropriate bacterial antigen in 16 of 17 (94%) definite etiology patients and CIE detected 11 (64%). In 17 probable etiology patients, bacterial antigens were detected by coagglutination in 15 (88%) and by CIE in 7 (41%). Only 1 pathogen was falsely identified in the 19 culture-negative control patients, indicating a high degree of specificity for both tests. Coagglutination was more sensitive than CIE (p less than 0.05) or sputum stained with Gram's stain (p less than 0.05) in correctly identifying the putative pathogen in sputum. Our results strongly suggest that coagglutination is a useful diagnostic technique for establishing a rapid etiologic diagnosis in community-acquired pneumonia.