Detection of soluble Pseudomonas aeruginosa antigens in bronchial secretions by a coagglutination test.

The coagglutination test was used for the detection of soluble Pseudomonas aeruginosa antigens in 165 bronchial secretions collected from critically ill patients with pulmonary infection. Of 57 cultures positive for Pseudomonas aeruginosa, 41 were positive by the coagglutination test. The test had a specificity of 97%, a sensitivity of 72%, a positive predictive value of 93% and a negative predictive value of 87% when compared with agar culturing. Quantitation of bacterial growth indicated that some Pseudomonas aeruginosa isolates were probably strains colonizing the bronchial tree of intubated patients rather than the etiologic agent of infection. When these specimens were excluded, the sensitivity and negative predictive value were 87% and 94.6%, respectively. The coagglutination test cannot replace isolation methods, but it is a rapid and useful procedure to screen patients suspect for pulmonary infection caused by Pseudomonas aeruginosa, providing a presumptive diagnosis when the result is positive.