Pneumococcal pericarditis. Diagnostic usefulness of counterimmunoelectrophoresis and computed tomographic scanning.

Although counterimmunoelectrophoresis (CIE) analysis of cerebrospinal fluid has proved useful in the diagnosis of meningitis, there has been little experience with its use in analyzing pericardial fluid. We describe two patients with pneumococcal pneumonia whose hospital course was complicated by purulent pericarditis. In one patient, results of a computed tomographic scan were important in suggesting the diagnosis. Results of a Gram's stain and culture of pericardial fluid failed to yield any organisms, presumably because both patients had received nine days of beta-lactam antibiotic therapy. However, the results from CIE analysis of pericardial fluid in both cases were positive for Streptococcus pneumoniae. In one patient, for whom capsular typing of the organism was performed, the pneumococcus type isolated from pericardial fluid matched the type isolated previously from a blood sample. The results of CIE can allow focused antibiotic therapy by establishing the correct diagnosis.