Detection of bacterial antigen in pleural fluid by counterimmunoelectrophoresis

Pleural fluid specimens from 87 patients were studied using counterimmunoelectrophoresis with pneumococcal, staphylococcal, and Hemophilus influenza b antisera. This method compared favorably with traditional bacteriologic methods and in addition provided a presumptive etiologic diagnosis in more than half of the specimens with negative bacterial cultures. One cross-reaction between H. influenza b antiserum and a pleural fluid specimen with an Escherichia coli isolate was observed.