[Usefulness of Streptococcus pneumoniae urinary antigen detection kit and the duration and intensity of reactivity with urinary antigen in patients with pneumonia].

We evaluated a rapid urinary antigen detection kit, Binax Now Streptococcus pneumoniae (Binax Inc., USA), which detects S. pneumoniae antigen in urine by immunochromatographic membrane assay, in 379 patients with presumptive pneumonia (total: 454 urine samples). S. pneumoniae antigen was detected in 64 (34%) of 188 patients. In all 64, pneumonia was diagnosed clinically, and there were 11 intense reactivity cases, 27 intermediate cases, and 26 weak cases. We found only two patients with positive sputum cultures for S. pneumoniae among 26 patients with weak reactivity to urinary antigen. The weak urinary antigen reactivity seems to include a false-positive result for S. pneumoniae pneumonia. There were five patients with negative results in whom S. pneumoniae was isolated (false-negative). We took intense and intermediate reactivity to be positive in order to diagnose pneumococcal pneumonia, and the kit showed a sensitivity of 72% and a specificity of 94% in 379 patients. The urinary antigen kit allowed us to diagnose 80% more patients with pneumococcal pneumonia than the use of conventional bacteriological diagnosis alone. There was no significant difference in the initial clinical characteristics, or in the severity of pneumonia among the three groups, according to the color intensity reached using the kit--weak, intermediate, and intense for the reactivity of urinary antigen. The duration of reactivity with S. pneumoniae urinary antigen did not correlate with the clinical characteristics or the severity of pneumonia. We concluded that S. pneumoniae urinary antigen detection kit is a useful adjunct to culturing for determining the etiology of pneumonia.