title: Pneumococcal antigen detection in bronchoalveolar lavage fluid from patients with pneumonia.
abstract: BACKGROUND
  Pneumococcal pneumonia can be diagnosed by the detection of capsular antigen in sputum, serum, pleural fluid, or urine using countercurrent immunoelectrophoresis and latex agglutination. In addition, quantitative cultures of bronchoalveolar lavage (BAL) fluid are also reliable for establishing the aetiology of pneumonia. This study investigated 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 agglutination. Patients were grouped according to BAL quantitative culture results 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 countercurrent immunoelectrophoresis in 50% and by latex agglutination in 54% of cases. In patients with pneumonia of unknown aetiology pneumococcal antigen was detected by latex agglutination in 53% of cases. Antigen was not detected in patients with pneumonia of other known aetiology or in control patients, yielding a specificity of 100%.
  
  
  CONCLUSIONS
  In patients with pneumococcal pneumonia requiring fibreoptic bronchoscopy detection of pneumococcal antigen in BAL fluid may rapidly and accurately confirm the aetiology. Furthermore, in nearly half the cases of pneumonia of unknown aetiology antigen can be detected, suggesting that Streptococcus pneumoniae is a major causative agent in such patients.
authors.affiliation: Unidad de Enfermedades Respiratorias, Facultad de Medicina, Universidad Austral de Chile.
authors.forename: P
authors.initials: P
authors.lastname: Jiménez
authors.forename: M
authors.initials: M
authors.lastname: Meneses
authors.forename: F
authors.initials: F
authors.lastname: Saldías
authors.forename: M
authors.initials: M
authors.lastname: Velásquez
mesh_terms: D000942:Antigens, Bacterial / Q000032:analysis*; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology*; D001999:Bronchoscopy; D003378:Counterimmunoelectrophoresis; D006801:Humans; D007841:Latex Fixation Tests; D011014:Pneumonia / Q000276:immunology* / Q000382:microbiology; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial