Testing done on pericardial fluid will not usually tell you whether a pericardial effusion is transudative or exudative, because this has little diagnostic value. In this video, you'll find out why that's the case and how to determine the cause of a pericardial effusion so you can take next steps.
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In contrast to investigations of other body fluids, establishing whether a pericardial effusion is transudative or exutative does not have significant diagnostic value. As such, parameters to differentiate between exudative, and transudative effusions such as protein, glucose, and lactate dehydrogenase, are not tested on pericardial fluid.
If the initial history and physical examination do not suggest a specific diagnosis, extensive laboratory testing, seeking an etiology is unlikely to be helpful. Some patients with pericardial effusion have an idiopathic cause. Gram stain, acid-fast bacilli stain and bacterial cultures would need to be done on the pericardial fluid if infection is suspected to be the cause.
If tuberculous pericarditis is suspected, culture should be done along with adenosine deaminase, interferon gamma, and lysozyme testing. PCR studies can be performed for viral infections, for example identifying cytomegalovirus in a transplant patient. However, the yield of PCR remains fairly low in many instances. Cytology is also helpful to rule out malignancies. Further testing can be done on the serum to look for other causes of pericardial effusion. The complete blood count would highlight leukocytosis or lymphocytosis due to an infectious cause.
Leukocytosis would also be seen in inflammatory states, and after myocardial infarction. Chemistry profile and renal function tests would establish renal failure. Thyroid function tests would naturally help to identify hypothyroidism. Chest x-ray would confirm the presence of pericardial fluid, allow us to evaluate the lung for tumors, and check for aortic dissection.
Lastly, a serum antinuclear antibody test should be considered in a young woman with an effusion, and associated acute pericarditis, since rarely this can be the initial presentation of systemic lupus erythematosus.