Evaluation of the rapid immunochromatographic ODK0501 assay for Streptococcus pneumoniae antigen detection with nasopharyngeal swabs: preliminary report

BACKGROUND Early identification and control of pathogenic bacteria are important in the treatment of pneumonia. Currently, two rapid antigen detection kits for pneumococcal pneumonia are available: one uses urine samples and the other, named RAPIRUN® S. pneumoniae, uses sputum samples. RAPIRUN® has shown high sensitivity with nasopharyngeal swab samples from pediatric patients. In this study, we investigated the performance of RAPIRUN® with nasopharyngeal swabs from adult patients. METHODS All adult patients diagnosed with pneumonia from November 2011 to April 2012 in St. Luke's International hospital were included in this cross-sectional study. Single sputum, nasopharyngeal swab, and urine samples obtained from patients were investigated using a rapid antigen detection kit. Sputum and blood cultures were also evaluated. We compared the characteristics of pneumococcal pneumonia patients diagnosed using RAPIRUN with a nasopharyngeal swab to those patients diagnosed using other methods. Sensitivity and specificity were also calculated. RESULTS Seventeen out of 60 patients with pneumonia were diagnosed with pneumococcal pneumonia. In 4 out  of the 17 cases, a positive test result was obtained using RAPIRUN with a nasopharyngeal swab. The sensitivity and specificity were 23.5 and 100 %, respectively. CONCLUSION RAPIRUN performed with nasopharyngeal swabs from adult patients exhibited lower sensitivity for the diagnosis of pneumococcal pneumonia than the other compared methods. The causative pathogen of pneumonia should be identified using not only sputum cultures or rapid antigen detection kits but also clinical features or gram staining of sputum.