The Test Sample
What is being tested?
Pericardial fluid is a liquid that acts as a lubricant for the movement of the heart. It is found in small quantities between the two layers of the pericardium. Pericardial fluid is produced by mesothelial cells in the membranes and acts to reduce 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 make a diagnosis as to 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. This type of fluid may be the result of conditions such as infection, malignancies (metastatic cancer, lymphoma, mesothelioma), or autoimmune disease.
Differentiation between the types of fluid is important because it helps diagnose the specific disease or condition. Doctors and laboratorians use an initial set of tests (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 sample of fluid is collected from the pericardial sac by a doctor with a syringe and needle using a procedure called a 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.