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Types of Body Fluid Testing

Laboratory testing can be performed on many types of fluids from the body other than blood. Often, these fluids are tested instead of blood because they can give more direct answers to what may be going on in a particular part of the body.

Some body fluids that may be tested include:

Additionally, saliva testing is becoming more common for some laboratory testing, such as HIV testing, drugs abuse testing and genetic tests.

Samples are usually obtained through collection of the fluid in a container (e.g., urine, semen) or by inserting a needle into the body cavity and aspirating with a syringe a portion of the fluid (e.g., CSF, pericardial fluid). For additional general information on how various samples are collected, see Collecting Samples for Testing.

Once a sample is obtained, a variety of tests may be performed, including chemistry tests, microscopic examinations, genetic tests, and infectious disease tests.

For certain body fluids, including pleural, pericardial, and peritoneal fluids, it is important to determine through testing whether the fluid is a transudate or an exudate because it can help diagnose the disease or condition present.

Transudate

  • Caused by an imbalance between the pressure within blood vessels (which drives fluid out) and the amount of protein in blood (which keeps fluid in)
  • It is a clear fluid with a low protein concentration and a limited number of white blood cells.
  • Seen in conditions such as congestive heart failure and cirrhosis

Exudate

  • Caused by injury and/or inflammation
  • It has a higher than normal protein content and may be cloudy due to increased numbers of cells.
  • Seen in conditions such as infections, malignancies (metastatic cancer, lymphoma, mesothelioma) or autoimmune diseases

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View Source

Block, D and Florkowski, C., Body Fluids. In: Rifai N, ed. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. St Louis, MO: Elsevier; 2018: Chap 43.

 

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