Evaluation of the immunochromatographic Binax NOW assay for detection of Streptococcus pneumoniae urinary antigen in a prospective study of community-acquired pneumonia in Spain.

Abstract

We evaluated the Binax NOW rapid immunochromatographic membrane test (ICT) for detection of Streptococcus pneumoniae urinary antigen in a population-based prospective study of adults with community-acquired pneumonia (CAP). ICT was performed with urine samples obtained from 452 (91.7%) of 493 patients enrolled. Pneumococcal antigen was detected in 19 (70.4%) of 27 patients with pneumococcal pneumonia. The test results were more frequently positive for patients who had not received antibiotics before testing (26.6% vs. 12.1%; P=.002). Only 16 (10.3%) of 156 samples obtained from patients with nonpneumococcal pneumonia yielded a positive result. Of the 269 patients who had pneumonia with no pathogen identified, antigen was detected in 69 (25.7%). With conventional microbiological criteria used as the "gold standard," the test had a sensitivity of 70.4% and a specificity of 89.7%. Testing concentrated urine samples with the ICT may be a useful technique for rapid diagnosis of pneumococcal pneumonia in adults with CAP.