The Test Sample
What is being tested?
Blood is a mixture of cells and plasma. The packed cell volume (PCV) is a measurement of the proportion of blood that is made up of cells. The value is expressed as a percentage or fraction of cells in blood. For example, a PCV of 40% means that there are 40 millilitres of cells in 100 millilitres of blood.
Red blood cells account for nearly all the cells in the blood. The PCV rises when the number of red blood cells increases or when the total blood volume is reduced, as in dehydration. The PCV falls to less than normal, indicating anaemia, when your body decreases its production of red blood cells or increases its destruction of red blood cells.
How is the sample collected for testing?
A sample is obtained by taking blood through a needle placed in a vein in the arm or by a finger-prick (for children and adults) or a heel-prick (for newborns).
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 test preparation is needed.