George Farmer and the Hematocrit
The hematocrit test measures the volume percentage of red blood cells in the blood. It is abbreviated as HCT, and is also known as the packed cell volume (PCV). This test is a major part of a person’s blood count results, along with hemoglobin concentration, WBC count, and platelet count. Normal levels vary from 40.7-50.3% for men and 36.1-44.3% for women.
To calculate the hematocrit level, centrifuge the blood in a microhematocrit (capillary) tube at 10,000 rpm for about 5 minutes, separating the blood into layers. Find the PCV by calculating the volume of red blood cells divided by the total volume of the sample; you can also measure the lengths of the layers if using the tube. Calculating the hematocrit using an automated analyzer by multiplying the red cell count by the mean cell volume is more accurate because the PCV may also include plasma surrounding the red blood cells. The hematocrit can be estimated by tripling the hemoglobin concentration and changing the units to percentage.
However, there are cases where the hematocrit will not be accurate. If red cells are being supplied, the hematocrit will be artificially high because the sample will contain a large amount of red cells. There are several diseases and disorders associated with high hematocrit levels, including dengue shock syndrome, polycythemia vera, capillary leak syndrome, chronic obstructive pulmonary disease, and other conditions associated with hypoxia. Also, the use of anabolic androgenic steroid can increase the amount of RBCs in the blood and increase the hematocrit. Dehydration is also a cause for a high hematocrit. If saline or other fluids are being supplied, they will dilute the sample and cause the hematocrit to be artificially low. Some conditions that may lead to a low hematocrit include destruction of RBCs, leukemia, malnutrition, iron/folate/B12/B6 deficiencies, and overhydration.
This test is important because it indicates whether you have...