Antigen detection in oropharyngeal secretions for rapid diagnosis of pneumococcal pneumonia

To determine the value of detection of antigen in the oropharynx in the diagnosis of pneumococcal pneumonia, oropharyngeal secretions were cultured for the presence of Streptococcus pneumoniae and tested for the presence of pneumococcal antigen. Sputum (if available) collected on the same day was also investigated for the presence of antigen. Detection of pneumococcal antigen was found to be directly related to the severity of pneumococcal carriership or infection (p <0.0001) and was not related to culture results. Patients with pneumococcal pneumonia had the highest antigen detection rate (38 %), followed by patients with pneumonia of unknown etiology (32 %) and patients with an acute lower respiratory tract infection due to Streptococcus pneumoniae (20 %). Pneumococcal carriers had a detection rate of only 9 %. Antigen could be detected in only one patient of the control groups. Although antigen detection in sputum was superior to that in oropharyngeal secretions, concordant results were obtained in 8 (40 %) and 6 (36 %) patients with pneumococcal pneumonia and pneumonia of unknown etiology respectively. The results strongly suggest that pneumococcal carriage seldom leads to a detectable level of antigen, and that antigen detection in the oropharynx appears to be of additive value in the diagnosis of pneumococcal pneumonia.