Evaluation of a rapid immunochromatographic ODK0501 assay for detecting Streptococcus pneumoniae antigen in sputum samples from patients with lower respiratory tract infection.

A novel, rapid, and noninvasive test (ODK0501) to detect Streptococcus pneumoniae antigen was evaluated in a Japanese multicenter study. ODK0501 uses polyclonal antibodies to detect C polysaccharide of S. pneumoniae from sputum samples by an immunochromatographic assay. The utility of ODK0501 was evaluated for 161 adult patients with lower respiratory tract infection between March 2006 and March 2007. Bacterial culture and identification, real-time PCR, and ODK0501 assays were performed on sputum samples, and the Binax Now Streptococcus pneumoniae antigen test was performed using urine samples obtained from the same patients. The performances of all tests were compared based on the results of bacterial culture and identification. The sensitivity and specificity of ODK0501 were 89.1% (49/55 samples) and 95.3% (101/106 samples), respectively. We then compared the Binax Now Streptococcus pneumoniae antigen test with ODK0501 using samples from 142 patients. The sensitivities of ODK0501 and the Binax Now S. pneumoniae antigen test were 90.0% (45/50 samples) and 62.0% (31/50 samples), respectively (P = 0.002). The relative quantity of S. pneumoniae in expectorated sputum was calculated using real-time PCR and indicated that the possibility of false-positive results for ODK0501 due to indigenous S. pneumoniae was low. The positive and negative concordance rates of ODK0501 and Binax Now were 96.8% (30/31 samples) and 21.1% (4/19 samples), respectively. Binax Now was less capable of detecting S. pneumoniae antigen among patients with underlying chronic obstructive pulmonary disease. In conclusion, ODK0501 is noninvasive, rapid, and an accurate tool for diagnosing respiratory infection caused by S. pneumoniae.