Blood Test for Eosinophils: What the EOS Results Mean
written by: R. Elizabeth C. Kitchen•edited by: Emma Lloyd•updated: 7/21/2010
The EOS blood test determines the number of eosinophils in a blood sample. This information can help physicians determine the cause of some symptoms.
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Eosinophils are a type of white blood cell that becomes active when certain infections, allergic diseases, or medical conditions are present. An EOS blood test is done to measure how many eosinophils are in the body. When there are too many or too little of these white blood cells, it can indicate a disease or condition.
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How is the Test Performed?
The blood that is tested is drawn from a vein, most often a vein in the hand or arm. The puncture site will be cleaned with an antiseptic and a tourniquet applied just above the puncture site. A needle is then inserted into the chosen vein, where a syringe or airtight vial collects enough blood for the test. The tourniquet is then removed, the healthcare provider ensures the vial or syringe has enough blood, then the needle is removed from the vein. The puncture site is then covered and pressure is applied to stop any bleeding.
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How to Prepare for the Test
Adults will not have to do anything to prepare. However, they must tell their doctor about any medications they take regularly before this blood test. Certain medications can increase the amount of eosinophils a patient has, including:
Certain laxatives including psyllium
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What to Expect During this Blood Test
Most patients will do fine with this test and any discomfort will be very minor. What patients feel vary and some describe what they feel as moderate pain, some describe it as a prick, and some state they feel some stinging. After the blood is drawn and the needle is removed, there may be some throbbing and bruising.
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Why is an EOS Blood Test Performed?
If the results of another blood test called a blood differential are abnormal, this blood test may be ordered. If a specific disease is suspected, this test may also be ordered. This test may assist in diagnosing: