Role of biochemical tests in the diagnosis of large pericardial effusions.

STUDY OBJECTIVES: To determine the biochemical characteristics of large pericardial effusions in various disease states, and to assess their utility as diagnostic tools. SETTING: An academic university hospital in the Western Cape, South Africa. DESIGN: Consecutive, prospective case series. PATIENTS: One hundred ten hospital patients > 12 years old, who presented to the echocardiography department with large pericardial effusions, and 12 control subjects who underwent open-heart surgery (coronary artery bypass graft or aortic valve replacement). MEASUREMENTS: Fluid was sent for examination of biochemistry, adenosine deaminase, microbiology, hematology, and cytology. The etiology of each pericardial fluid sample was established using predetermined criteria. RESULTS: The biochemistry of pericardial exudates differed significantly from pericardial transudates. Light' s criteria (whereby an exudate is defined as having one or more of the following: pleural fluid/serum protein ratio > 0.5; pleural fluid/serum lactate dehydrogenase [LDH] ratio > 0.6; and/or pleural fluid LDH level > 200 U/L) were applied to pericardial fluids and demonstrated to be the most reliable diagnostic tool for identifying pericardial exudates. The corresponding sensitivity was 98%. CONCLUSION: Although laboratory tests are a useful guideline when assessing the etiology and pathophysiology of pericardial effusions, the majority of large, clinically significant pericardial effusions result from exudative causes.