Image Caption : Blood Smear Showing Reduced Red Blood Cell Count : Anemia is caused when there are too few RBCs circulating in the bloodstream. That can happen when they are lost through bleeding, destroyed too quickly or produced too slowly. When a person is anemic, the blood is less effective at transporting inhaled oxygen to cells and retrieving carbon dioxide from the tissues and carrying it back to the lungs to be exhaled.
The volume of packed RED BLOOD CELLS in a blood specimen. The volume is measured by centrifugation in a tube with graduated markings, or with automated blood cell counters. It is an indicator of erythrocyte status in disease. For example, ANEMIA shows a low value; POLYCYTHEMIA, a high value.
National Center for Biotechnology Information, U.S. National Library of Medicine
The hematocrit is another way to look at the function of your red blood cells. Your blood is composed of several different components, the main ones being red and white blood cells and the liquid portion know as blood serum. The proportions of these components is critical; the hematocrit measures the percentage of blood that is made up of red blood cells, and this, in turn, depends on the number and size of red blood cells.
Why test for hematocrit:
The hematocrit is not a molecule or some other component of blood; it is instead a simple mathematical calculation. Specifically, it is the percentage of your total blood volume (whole blood) that is made up of red blood cells. If there are 45 milliliters of red blood cells in a 100 milliliter sample of whole blood, the hematocrit is 45%.
Anemia (of all types) affects 2 billion people worldwide, or about 30% of the world's population. Most common causes are iron deficiency, malnutrition and blood loss from parasites. In the U.S. about 8% of the population suffers from anemia, with rates in children more than twice that.
Complete Blood Count
Often, the first test used to diagnose anemia is a complete blood count (CBC). The CBC measures many parts of your blood.
The test checks your hemoglobin and hematocrit (hee-MAT-oh-crit) levels. Hemoglobin is the iron-rich protein in red blood cells that carries oxygen to the body. Hematocrit is a measure of how much space red blood cells take up in your blood. A low level of hemoglobin or hematocrit is a sign of anemia.
The normal range of these levels might be lower in certain racial and ethnic populations. Your doctor can explain your test results to you.
The CBC also checks the number of red blood cells, white blood cells, and platelets in your blood. Abnormal results might be a sign of anemia, another blood disorder, an infection, or another condition.
Finally, the CBC looks at mean corpuscular (kor-PUS-kyu-lar) volume (MCV). MCV is a measure of the average size of your red blood cells and a clue as to the cause of your anemia. In iron-deficiency anemia, for example, red blood cells usually are smaller than normal.
National Heart, Lung, and Blood Institute / NIH
The hematocrit (Ht or HCT, from the Greek "αιματοκρίτης" which means 'blood judge'), also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally 45% for men and 40% for women. It is considered an integral part of a person's complete blood count results, along with hemoglobin concentration, white blood cell count, and platelet count. Because the purpose of red blood cells is to transfer oxygen from the lungs to body tissues, a blood sample's hematocrit—the red blood cell volume percentage—can become a point of reference of its capability of delivering oxygen. Additionally, the measure of a subject's blood sample's hematocrit levels may expose possible diseases in the subject. Anemia refers to an abnormally low hematocrit, as opposed to polycythemia, which refers to an abnormally high hematocrit. For a condition such as anemia that goes unnoticed, one way it can be diagnosed is by measuring the hematocrit levels in the blood. Both are potentially life-threatening disorders.
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