Detection of pneumococcal polysaccharide in the sputum of patients with pneumococcal pneumonia by counterimmunoelectrophoresis.

Each of 41 patients with bacterial pneumonia was placed into 1 of 4 categories based on the relative clinical certainty of the diagnosis of pneumococcal pneumonia. The frequency of pneumococcal polysaccharide in the sputum by counterimmunoelectrophoresis (CIE) was then noted for each diagnostic category of patients. Detection of pneumococcal polysaccharide in sputum correlated with the diagnostic certainty of pneumococcal pneumonia, while results of culture of sputum were less indicative of pneumococcal infection. Saliva of 83 normal individuals failed to give positive tests for pneumococcal polysaccharide despite the presence of alpha-hemolytic streptococci on culture. Furthermore, the mere presence of pneumococci in cultures did not predict a positive test for polysaccharide by CIE nor did the absence of pneumococci mean that polysaccharide would not be detected. This study suggests that detection of pneumococcal polysaccharide appears more rapid, more sensitive, and more specific than sputum cultures in diagnosing pneumococcal infection of the lung.