PNEUMOCOCCAL ANTIGEN-DETECTION IN BRONCHOALVEOLAR LAVAGE FLUID FROM PATIENTS WITH PNEUMONIA

Background - Pneumococcal pneumonia can be diagnosed by the detection of capsular antigen in sputum, serum, pleural fluid, or urine using co untercurrent immunoelectrophoresis and latex agglutination. In additio n, quantitative cultures of bronchoalveolar lavage (BAL) fluid are als o reliable for establishing the aetiology of pneumonia. This study inv estigated the value of rapid detection of pneumococcal antigen in BAL fluid from patients with pneumonia. Methods - Pneumococcal antigen was detected by countercurrent immunoelectrophoresis and latex agglutinat ion. Patients were grouped according to BAL quantitative culture resul ts into pneumococcal pneumonia (n = 24), other known aetiology (n = 18 ), and unknown aetiology (n = 17). Thirteen patients with interstitial lung disease and without pneumonia served as a control group. Results - In patients with pneumococcal pneumonia, antigen was detected by co untercurrent immunoelectrophoresis in 50% and by latex agglutination i n 54% of cases. In patients with pneumonia of unknown aetiology pneumo coccal antigen was detected by latex agglutination in 53% of cases. An tigen was not detected in patients with pneumonia of other known aetio logy or in control patients, yielding a specificity of 100%. Conclusio ns - In patients with pneumococcal pneumonia requiring fibreoptic bron choscopy detection of pneumococcal antigen in BAL fluid may rapidly an d accurately confirm the aetiology. Furthermore, in nearly half the ca ses of pneumonia of unknown aetiology antigen can be detected, suggest ing that Streptococcus pneumoniae is a major causative agent in such p atients.