Detection of penumococcal antigens in the sputum in pneumococcal pneumonia

Forty-seven patients with bacterial pneumonia were grouped by use of clinical criteria according to the relative certainty of a diagnosis of pneumococcal pneumonia. Sputums were tested for pneumococcal antigens by counterimmunoelectrophoresis with polyvalent pneumococcal antiserum. Antigens were detected in the sputum of 29 of 39 patients with evidence of pneumococcal pneumonia, and there was good correlation between the detection of antigens and the degree of certainty of the clinical diagnosis. Antigens persisted briefly in the sputum during therapy with antimicrobial drugs and could be detected during the first 48 hours of therapy in most cases of pneumococcal pneumonia. Pneumococci were isolated from the sputum in only 18 of 39 cases of pneumococcal pneumonia, and sputum cultures did not correlate as well as counterimmunoelectrophoresis with clinical diagnoses. In studies of 27 patients with chronic bronchitis without pneumonia, pneumococci were isolated from sputum in 10 cases, whereas counterimmunoelectrophoresis was positive in 5 cases. Counterimmunoelectrophoresis provides a simple and rapid method for detecting pneumococcal antigens in sputum, and it appears to be more reliable than sputum cultures in establishing a presumptive diagnosis in pneumococcal pneumonia.