Pericardial fluid analysis is used to help diagnose the cause of inflammation of the pericardium (pericarditis) and/or fluid accumulation around the heart (pericardial effusion). An initial set of tests (protein or albumin, cell count and appearance) is used to differentiate between the two types of fluid that may be produced (transudate and exudate). Additional tests on the fluid itself may be used to help distinguish possible conditions causing an exudate:
Infectious diseases - caused by viruses, bacteria, or fungi. Infections may originate in the pericardium or spread there from other places in the body. For example, pericarditis may follow a respiratory infection.
Pericardial fluid analysis may be requested when a doctor suspects that a patient has a condition or disease that is causing pericarditis and/or pericardial effusion. It may be used when a patient has some combination of the following signs and symptoms:
Chest pain, sharp or sometimes dull, that may be relieved by bending forward
Exudates can be caused by a variety of conditions and diseases and usually require further testing to aid diagnosis. Exudates may be caused by, for example, infections, trauma, various cancers, or pancreatitis. The following is a list of additional tests that the doctor may order depending on the suspected cause:
Physical characteristics – the normal appearance of a sample of pericardial fluid is straw coloured and clear. Abnormal results may give clues to the conditions or diseases present:
Milky appearance—may point to lymphatic system involvement
Reddish pericardial fluid may indicate the presence of blood
Cloudy thick pericardial fluid may indicate the presence of microorganisms and/or white blood cells
Chemical tests –in addition to protein or albumin, a glucose test may be performed. Glucose in pericardial fluid samples is typically about the same as blood glucose levels. It may be lower with infection.
Microscopic examination – Normal pericardial fluid has small numbers of white blood cells (WBCs) but no red blood cells (RBCs) or microorganisms. Laboratories may examine drops of the pericardial fluid and/or use a special centrifuge (cytocentrifuge) to concentrate the fluid’s cells at the bottom of a test tube. Samples are placed on a slide, treated with special stain, and an evaluation of the different kinds of cells present is performed.
Total cell counts—quantity of WBCs and RBCs in the sample. Increased WBCs may be seen with infections and other causes of pericarditis.
WBC differential—determination of percentages of different types of WBCs. An increased number of neutrophils may be seen with bacterial infections.
Cytology – a cytocentrifuged sample is treated with a special stain and examined under a microscope for abnormal cells. This may be done when a mesothelioma or metastatic cancer is suspected. The presence of certain abnormal cells, such as tumour cells or immature blood cells, can indicate what type of cancer is involved.
Infectious disease tests – routine tests may be performed to look for microorganisms if infection is suspected:
Gram stain - for direct observation of bacteria or fungi under a microscope. There should be no organisms present in pericardial fluid.
Bacterial culture and susceptibility testing - used to detect any microorganisms, which will grow in the culture. If bacteria are present, susceptibility testing can be performed to guide antimicrobial therapy. If there are no microorganisms present, it does not rule out an infection; they may be present in small numbers or their growth may be inhibited because of prior antibiotic therapy.
Increased amounts of pericardial fluid also can restrict the movement of the heart. Cardiac tamponade is when pericardial fluid builds up to the point that pressure on the heart prevents it from filling normally. Rapid fluid build-up can be a medical emergency, causing heart failure and death. When fluid accumulates slowly, the pericardial sac stretches and symptoms gradually worsen.
This article was last reviewed on 7 December 2012. | This article was last modified on 28 March 2013.
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