Utility of a Sputum Antigen Detection Test in Pneumococcal Pneumonia and Lower Respiratory Infectious Disease in Adults

Objective To compare the utility of Gram staining, a urinary antigen detection kit and a sputum antigen detection kit were examined for the rapid and early detection of pneumococcal pneumonia and lower respiratory infectious diseases. Methods A newly developed sputum pneumococcal antigen detection kit (RAPIRUN), Gram staining, and urinary antigen detection kit (BinaxNOW) were comparatively evaluated for their ability to detect Streptococcus pneumoniae in patients with pneumonia or lower respiratory tract infection. Sputum culture results were used as a standard for comparison. Furthermore, the pneumococcus-positive rates in culture and rapid tests were compared using polymerase chain reaction (PCR) as a reference. Results Of the 169 patients studied, 54 (32.0%) tested positive for S. pneumoniae in culture. S. pneumoniae detection sensitivities for Gram staining, RAPIRUN, and BinaxNOW were 75.9%, 90.7%, and 53.7%, respectively; thus, RAPIRUN had a significantly higher sensitivity than BinaxNOW (p < 0.001). For patients with >= 105 copies/mu g of pneumococcal surface protein A DNA PCR analysis, the detection rates of culture, Gram staining, and RAPIRUN were 85.2%, 72.1%, and 82.0%, respectively, however, the detection rate of BinaxNOW was only 47.5%. Comparisons among 45 patients with culture-positive pneumococcal pneumonia revealed that RAPIRUN had a significantly higher detection rate than BinaxNOW in the mild cases (p < 0.006), regardless of the number of days from onset (p < 0.03). Conclusion RAPIRUN is a rapid testing kit that detects S. pneumoniae in sputum with a high sensitivity and specificity. It is a particularly more useful detection kit than BinaxNOW for early and mild community-acquired pneumonia in pre-treatment patients whose sputum specimens can be obtained.