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The Test Sample
What is being tested?
The pericardium is a two-layered, sac-like membrane that surrounds the heart. Pericardial membranes produce pericardial fluid, a liquid that sits between the pericardium's membranes. The fluid acts as a lubricant for the movement of the heart, reducing friction as the heart pumps blood.
A variety of conditions and diseases can cause inflammation of the pericardium (pericarditis) and/or excessive accumulation of pericardial fluid (pericardial effusion). Pericardial fluid analysis is a group of tests that evaluate this liquid to help diagnose the cause of the increased fluid.
The two main reasons for fluid accumulation in the pericardial space are:
- An imbalance between the pressure within blood vessels—which drives fluid out of blood vessels—and the amount of protein in blood—which keeps fluid in blood vessels. The fluid that accumulates in this case is called a transudate. Transudates are most often caused by congestive heart failure or cirrhosis.
- An injury or inflammation of the pericardium, in which case the fluid that accumulates is called an exudate. Conditions such as infections, malignancies (metastatic cancer, lymphoma, mesothelioma), or autoimmune disease may cause the accumulation of exudate.
Determining if the increased fluid is transudate or exudate is important because it helps narrow down the possible causes of pericardial fluid buildup. Healthcare practitioners and laboratorians use an initial set of tests, including cell count, protein or albumin level, and appearance of the fluid, to distinguish between transudates and exudates. Once the fluid is determined to be one or the other, additional tests may be performed to further pinpoint the disease or condition causing pericarditis and/or pericardial effusion.
How is the sample collected for testing?
A healthcare practitioner uses a syringe and needle to collect a fluid sample from the pericardial sac in a procedure called pericardiocentesis.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No special preparation is usually needed.