[Evaluation of the usefulness of a rapid immunochromatographic membrane test to detect Streptococcus pneumoniae antigen in the early diagnosis of pneumococcal respiratory tract infections and the relationship to the severity of pneumonia].

ABSTRACT

We evaluated the usefulness of a rapid immunochromatographic membrane test (Binax NOW Streptococcus pneumoniae kit; ICT) to detect Streptococcus pneumoniae antigen in early diagnosis of pneumococcal respiratory tract infections and the relationship to the severity of pneumonia. We diagnosed 155 of 592 samples, which were performed by ICT, as S. pneumoniae respiratory tract infections. Sixty-three samples (40.6%) exhibited mixed infection. We evaluated the severity of infection using the A-DROP system and compared positive rates. Pneumococcal antigen was detected in patients with severe or most severe pneumococcal infections as frequently as in those with mild or moderate infections. Meanwhile sputum gram staining yielded a lower detection rate in patients with severe or most severe infections than those with mild or moderate infections (P = 0.0046). Serum C-reactive protein levels increased in patients with severe penumococcal infection, but decreased in those with the most severe pneumococcal infection (P<0.0001). The test revealed a sensitivity of 67.7% and a specificity of 98.8%, and the diagnostic yield of pneumococcal pneumonia increased by 7.7% using ICT combined with conventional methods. In conclusion, ICT is a useful test for the early diagnosis of pneumococcal respiratory infections especially in adult patients with severe or most severe infections for whom demonstrative results of a sputum Gram stain is unavailable, even after commencement of antibiotic treatment.