An IgA test measures the blood level of immunoglobulin A, one of the most common antibodies in the body. Antibodies are proteins made by the immune system to fight bacteria, viruses, and toxins.
IgA is found in high concentrations in the body's mucous membranes, particularly the respiratory passages and gastrointestinal tract, as well as in saliva and tears.
IgA also plays a role in allergic reactions. IgA levels also may be high in autoimmune conditions, disorders in which the body mistakenly makes antibodies against healthy tissues.
Why It's Done
An IgA test can help doctors diagnose problems with the immune system, intestines, and kidneys. It may be done in kids who have recurrent infections. It's also used to evaluate autoimmune conditions, such as rheumatoid arthritis, lupus, and celiac disease. Kids born with low levels of IgA — or none at all — are at increased risk of developing an autoimmune condition, infections, asthma, and allergies.
Your doctor will tell you if any special preparations are required before this test. On the day of the test, having your child wear a T-shirt or short-sleeved shirt can make things easier for your child and the technician who will be drawing the blood.
A health professional will usually draw the blood from a vein. For an infant, the blood may be obtained by puncturing the heel with a small needle (lancet). If the blood is being drawn from a vein, the skin surface is cleaned with antiseptic, and an elastic band (tourniquet) is placed around the upper arm to apply pressure and cause the veins to swell with blood. A needle is inserted into a vein (usually in the arm inside of the elbow or on the back of the hand) and blood is withdrawn and collected in a vial or syringe.
After the procedure, the elastic band is removed. Once the blood has been collected, the needle is removed and the area is covered with cotton or a bandage to stop the bleeding. Collecting blood for this test will only take a few minutes.
Either method (heel or vein withdrawal) of collecting a sample of blood is only temporarily uncomfortable and can feel like a quick pinprick. Afterward, there may be some mild bruising, which should go away in a few days.
Getting the Results
The blood sample will be processed by a machine. The results are commonly available within a day or two. If results suggest an abnormality, the doctor may perform further tests.
This test is considered a safe procedure. However, as with many medical tests, some problems can occur with having blood drawn, like:
fainting or feeling lightheaded
hematoma (blood accumulating under the skin causing a lump or bruise)
pain associated with multiple punctures to locate a vein
Helping Your Child
Having a blood test is relatively painless. Still, many children are afraid of needles. Explaining the test in terms your child might understand can help ease some of the fear.
Allow your child to ask the technician any questions he or she might have. Tell your child to try to relax during the procedure, as tense muscles can make it harder and more painful to draw blood. It also may help for your child to look away when the needle is being inserted into the skin.
If You Have Questions
If you have questions about the IgA test, speak with your doctor.