The usefulness of diagnostic tests on pericardial fluid

Study objectives: To determine the physical, chemical, and cellular characteristics of pericardial fluid in various disease states and to assess their diagnostic accuracies. Setting: A metropolitan university hospital. Design: Consecutive case series. Patients: One hundred seventy-five hospital patients, aged. 1 month to 87 years, who had undergone pericardiocentesis (n=165) or control subjects who had undergone open heart surgery (n=10) between 1984 and 1996. Measurements: The appearance of pericardial fluid and results of chemistry tests, cell counts, cytologic studies, Gram's stain, and microbial cultures were obtained by chart review, The etiology of each pericardial fluid sample was determined using prospective diagnostic criteria. Results: Exudates differed from transudates by higher leukocyte counts and ratios of fluid to serum lactate dehydrogenase levels. Fluid glucose levels were significantly less in exudates. Sensitivity for detecting exudates was high for specific gravity >1.015 (90%), fluid total protein >3.0 g/dL (97%), fluid to serum protein ratio >0.5 (96%), fluid lactate dehydrogenase ratio >0.6 (94%), and fluid to serum glucose ratio <1.0 (85%). None of these indicators were specific, Fluid total protein and specific gravity were moderately correlated (r=0.56). Fluid cytologic study had a sensitivity of 92% and specificity of 100% for malignant effusion. No other test was diagnostic for a specific etiology. Among infection-associated effusions, culture-positive fluid had more neutrophils, higher lactate dehydrogenase levels, and lower ratios of fluid to serum glucose than culture-negative (parainfective) fluid. Conclusions: Evaluation of pericardial fluid might be limited to cell count, glucose, protein, and lactate dehydrogenase determinations plus bacterial culture and cytology, While not used routinely, other tests that may be highly specific for particular diseases should be ordered only to confirm a high clinical suspicion.