Alternate Names: Eosinophils; Absolute eosinophil count
How Performed: Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
In the laboratory the blood is placed on a microscope slide and stained. Eosinophils will show granules that are an orange-red color. The number of eosinophil cells in a given area per 100 cells is counted. The percentage of eosinophils is multiplied by the WBC count to give the absolute eosinophil count.
How To Prepare: Adults:
No special preparation is necessary.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:
How It Feels: When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Risks:
- excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Why Performed: Little is known about the function of eosinophils. However, an eosinophil count may be ordered if the blood differential is abnormal, particularly if there is an increased eosinophil level.
The eosinophil count may also be ordered to:
- detect allergic reaction and assess the severity
- detect parasitic infection
- confirm Hodgkin’s disease
- assess for sensitivity to drugs (particularly some anticoagulants)
- confirm acute hypereosinophilic syndrome (rare but usually fatal leukemia-like condition)
Normal Values: Less than 350 cells/mcl
Note: cells/mcl = cells per microliter
Abnormal Results: Increased levels of eosinophils (eosinophilia) are most often associated with allergic diseases and with parasites (such as worms).
Disorders include:
Medications that may cause an increase in eosinophils include:- amphetamines (diet suppressants)
- tranquilizers
- bulk-type laxatives containing psyllium
- certain antibiotics
decreased eosinophils may be associated with:
Cost:
Special Considerations: The eosinophil count is nonspecific (it does not tell, for example, if an increase is caused by allergy or parasite infection). It is most often used to confirm a diagnosis.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
