Hematocrit is a measure that gives the proportion in volume of the blood made of red blood cells. The reading is expressed in form of percentage. Hematocrit test measures the percentage of blood volume, which is made of red blood cells. The measurement is based on the amount or number of red cells in blood and the size of each red cell. This test is part of the complete blood count test.
Hematocrit is measured from a sample of blood using machines that make other measurements and readings at the same time. Most of the machines do not directly measure hematocrit but they calculate it based on the hemoglobin and the average volume of red blood cells. A centrifuge may also manually determine the hematocrit reading.
Hematocrit test
A hematocrit test is done by using a sample of your blood. A medical lab technician takes the sample of your blood and puts it in a device called centrifuge. The sample is spun in a test tube and the spinning motions separate the blood sample into three components, which are the plasma or fluid component, the red blood cells, and the third part made up of other blood cells. After the separation, the technician is able to determine the proportion of cells that consist of red blood cells.
Hematocrit test may be performed if a person has signs of anemia, leukemia, diet deficiency, and other medical conditions, which affect the percentage of red blood cells. The normal ranges for hematocrit may different from young people and the old. Newborns have a range of between 55 and 68 percent. Adult males have a range between 42 and 54 percent while adult females may have hematocrit ranging from 38 to 46 percent. These values may slightly vary from one laboratory to another.
The accuracy of the test results may be affected by various conditions that cause the readings to be misleading and inaccurate. People living in high altitude may show variance in the results. Pregnant women and people who have recently lost blood may also have misleading results.
A patient who has recently had a blood transfusion may not show the exact results of the red blood cells counts. The same case occurs due to dehydration. The doctor will examine any possible complication factors, which may have led to inaccurate results and may interpret those results differently. A repeat test may be ordered in order to rule out the inaccuracies.
Low Hematocrit – Causes
When there is low hematocrit, it may indicate that a person is anemic. This condition may arise due to a number of reasons. If you have loss of blood, as may happen due to surgery, injury, colon cancer or bleeding, then it may lead to anemic situation. Nutritional deficiency characterized by lack of sufficient iron, folate, and vitamin B12 may cause anemia.
A person with bone narrow problems where the marrow is replaced with cancer cells, it may cause one to be anemic. Similarly, if the bone marrow is suppressed by chemotherapy drugs or a person has kidney failure, these problems may lead to low hematocrit levels. Moreover, abnormal hemoglobin caused by sickle cell anemia is also associated with low levels of hematocrit. Overhydration may be another cause of low hematocrit levels.
Lower than normal ranges of hematocrit may indicate a large number of white blood cells, which is initially available in small proportions in your blood. The elevated white blood cells may occur due to an infection, long-term illness, lymphoma, and other health conditions, which trigger the production of white blood cells. These white cells are part of the immune system and they are likely to be produced in large numbers when there is an infection.
Causes of high levels of hematocrit
If a person has higher than normal ranges of hematocrit, this means that there is an increased number of red blood cell counts. People living in high altitude areas seem to have high levels of hematocrit. Chronic smokers also have high levels of red blood cell counts. Dehydration can lead to false reading of high hematocrit, which disappears after the fluid balance is attained.
Moreover, there are less common causes of high red cell counts such as lung disease, and certain tumors. Polycythemia rubra vera, a disorder of the bone marrow may lead to high levels of red blood cells counts. People who abuse the drug erythripoietin or epogen especially athletes who take it for blood doping may witnessed increased percentage of their hematocrit levels.
Other conditions like pulmonary fibrosis and cor pulmonale are associated with elevated red blood cells counts. Disorders like polycythemia vera cause the body to produce large amounts of red blood cells. When conditions like heart and lung disease affect your body, they can lead to low oxygen levels.
If the body senses low levels of oxygen, it responds by making more of the red blood cells in order to step up the amount of oxygen in blood. This leads to higher than normal levels of hematocrit. The proportion of red blood cells when compared with all blood cells may be used as a marker for determining, diagnosing, and monitoring a patient’s response to treatment.