Blood cultures from 140 patients with chest infections were examined for the presence of pneumococcal antigen by both latex particle agglutination and counterimmunoelectrophoresis. Twenty-three samples (15 patients) were positive for pneumococcal antigen by counterimmunoelectrophoresis, of which 21 samples (13 patients) yielded Streptococcus pneumoniae in culture. Thirty-three samples (20 patients) were positive by latex particle agglutination, of which 24 samples (15 patients) were culture positive. The sensitivities and specificities were calculated and it was concluded that latex particle agglutination was the better test for the determination of the presence of pneumococcal capsular polysaccharide.
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