Validation of urinary antigen test for Streptococcus pneumoniae in patients with pneumococcal pneumonia

The study was undertaken to prospectively evaluate a Streptococcus pneumoniae urinary antigen test for diagnosis of pneumococcal pneumonia among patient and control groups between 2004 and 2006. Microbiological analysis for these patients included Gram staining for sputum, sputum and blood culture. Nonconcentrated urine samples were tested using an immunochromatographic assay, the NOW S.pneumoniae antigen test. The urinary antigen test was positive in 9 (15.3%) of 59 patients enrolled in the study and in 8 (73%) of 11 patients with pneumococcal pneumonia confirmed by conventional methods. The test revealed a sensitivity of 72.7% and a specificity of 97.6% with conventional microbiological criteria used as the reference standard. The positive predictive value was 88.9% and the negative predictive value was 93%. We concluded that the urinary antigen test can supplement conventional microbiological tests in the diagnosis of pneumococcal pneumonia.