Evaluation of a rapid immunochromatographic test for detection of Streptococcus pneumoniae antigen in urine samples from adults with community-acquired pneumonia

Streptococcus pneumoniae is the most common cause of community-acquired pne umonia but is undoubtedly underdiagnosed. Isolation of S. pneumoniae from b lood is specific but lacks sensitivity, while isolation of S. pneumoniae fr om sputum may represent colonization. We evaluated a new immunochromatograp hic test (NOW S. pneumoniae urinary antigen test; Binax, Portland, Maine) t hat is simple to perform and that can detect S. pneumoniae antigen in urine within 15 min. Urine samples from 420 adults with community-acquired pneum onia and 169 control patients who did not have pneumonia were tested. Urine from 315 (75%) of the pneumonia patients and all controls was tested both before and after 25-fold concentration, while the remaining 105 samples wer e only tested without concentration. S. pneumoniae urinary antigen tests we re positive for 120 (29%) patients with pneumonia and for none of the contr ols. Of the urine samples tested with and without concentration, 96 were po sitive, of which 6 were positive only after concentration. S. pneumoniae an tigen was detected in the urine from 16 of the 20 (80%) patients with blood cultures positive for S. pneumoniae and from 28 of the 54 (52%) patients w ith sputum cultures positive for S. pneumoniae. The absence of S. pneumonia e antigen in the urine from controls suggests that the specificity is high. Concentration of urine prior to testing resulted in a small increase in yi eld. The NOW S. pneumoniae urinary antigen test should be a useful adjunct to culture for determining the etiology of community-acquired pneumonia in adults.