Contribution of a pleural antigen assay (Binax NOW) to the diagnosis of pneumococcal pneumonia.
OBJECTIVE
To determine whether the detection of pneumococcal antigen in pleural fluid augments conventional microbiological methods used for the etiologic diagnosis of pneumonia.


METHODS
In this retrospective study, a rapid immunochromatographic test (ICT) [NOW Streptococcus pneumoniae assay; Binax; Scarborough, ME] was performed on pleural fluid samples from 34 patients with pneumonia due to S pneumoniae, 89 patients with effusions of nonpneumococcal origin, and 17 patients with pneumonia of unknown etiology. Data on blood cultures, pleural fluid cultures, and urinary antigen tests were recorded.


RESULTS
The ICT test result was positive in 24 of 34 patients (70.6%) with pneumococcal pneumonia and negative in 83 of 89 patients (93.3%) without pneumococcal pneumonia. The sensitivity of the pleural ICT test was higher than that obtained for blood (37.5%) and pleural fluid cultures (32.3%), but lower than the detection of pneumococcal antigen in urine samples (82.1%). However, three patients with pneumococcal pneumonia and a negative ICT urine test result had a positive pleural fluid antigen detection result test. Previous antibiotic exposure did not influence pneumococcal antigen detection in either pleural fluid or urine specimens. Six additional patients with empyema due to anaerobes (three patients), Streptococcus viridans (two patients), and Enterococcus faecalis (one patient) had false-positive pleural ICT test results. Finally, the ICT assay finding was also positive in 5 of 17 patients (29.4%) with pneumonia without a definite microbiological cause.


CONCLUSIONS
The ICT test performed on pleural fluid samples augments the standard diagnostic methods of blood and pleural fluid cultures, even in the case of prior antibiotic therapy, and enhances the ICT urinary antigen assay.
Porcel
José M
JM
Department of Internal Medicine, Pleural Diseases Unit, Arnau de Vilanova University Hospital, Avda Alcalde Rovira Roure 80, 25198 Lleida, Spain. jporcelp@yahoo.es
Ruiz-González
Agustín
A
Falguera
Miquel
M
Nogués
Antoni
A
Galindo
Carles
C
Carratalá
Jordi
J
Esquerda
Aureli
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000942:Antigens, Bacterial / Q000032:analysis*; D002845:Chromatography; D017714:Community-Acquired Infections / Q000175:diagnosis / Q000276:immunology; D005260:Female; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000276:immunology*; D011018:Pneumonia, Pneumococcal / Q000175:diagnosis* / Q000276:immunology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013296:Streptococcus pneumoniae / Q000276:immunology
D000942:Antigens, Bacterial