IgE test – Immunoglobulin E

What is an IgE test?

The immune system is our body’s primary defense mechanism against external infections. Allergies are caused when the immune system treats certain harmless substances, which may be from food items or pollen from a flower, as a threat. Substances that induce an allergic reaction are called allergens and the reaction can vary from mild sneezing to a more severe condition called anaphylactic shock.

As a defensive reaction to this perceived threat, the body produces antibodies called immunoglobulin E (IgE) which are a form of protein. The antibody binds itself to specialized mast cells in the tissues and a type of white blood cell, known as a basophil, in the bloodstream. An IgE blood test measures the amount of IgE antibodies present in the blood at any point.

The test can be specifically designed for a particular allergen or for a group of them which can be chosen from a list. The most common allergens that are found worldwide include pollen, dust mites, molds, animal dander, cockroach, insect venom, and certain foods. The test is also classified in various other ways and is termed as Quantitative IgE, Immunoglobulin E, Total IgE, or Specific IgE test at times. The measurement of IgE levels is necessary for patients who need to undergo the omalizumab (anti-IgE) therapy and determine the correct dosage.

Why do I need to test my IgE levels?

Your doctor can order you to undergo an IgE test in case you have a severe allergic reaction to any substance or some food component. There can be various symptoms for an allergic reaction, some of which are listed below.

– A running nose with sneezing.
– Watery and itchy eyes.
– Development of rashes or dermatitis on the body.
– Diarrhea and vomiting.
– Shortness of breath or whizzing.
– Unexplained weight loss or fevers that have no other reasons.

The test can also be suggested in order to monitor specific illnesses like AIDS or cancer.

How many people in India suffer from food allergies?

In India, roughly 1-2% of the general population is reported to have some form of food allergy. However, the degree to which people experience food allergy symptoms may vary greatly. Many people suffer from something known as “food hypersensitivity” where even minuscule ingestion of a particular kind of food can trigger a series of immunological reactions. It could range from moderate to severe and even turn into anaphylaxis with fatal consequences.

How is the IgE test performed?

A serum IgE test is performed by drawing a blood sample from a vein by inserting a needle which takes a few minutes. The method is safe and fast and you might feel a slight prick while the needle is being inserted. The blood sample is then tested for specific levels of IgE. The blood collection method includes the following steps.

– The skin around the vein from which blood is collected is cleaned.

– An elastic band is tied around the area to make the veins swell up with blood. The point chosen is generally around the elbow or at the back of the palm.

– A needle is inserted in the vein to draw the blood into a connected syringe.

– The elastic band is taken off and the needle is pulled out from the skin.

– In the case of some individuals, it can be difficult to find a vein so the healthcare professional may have to try more than once. For babies, blood is often drawn from the heel area through a tiny needle and the method is often termed as “heel stick collection.”

In some special cases, the test is also done through a collection of the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. In these cases, an anesthetic shot is administered to prevent any discomfort during the collection. A hollow needle is inserted in the space between two vertebrae in the lower spine to remove a small amount of the fluid.

What are the types of immunoglobulin antibodies that are found in the body?

In general, there are three major immunoglobulin antibodies found in the body.

– Immunoglobulin A:  These antibodies are found in the blood, saliva and the tears. They are also located in the mucous membranes of the lungs, sinuses, stomach, and intestines.

– Immunoglobulin G: This is the most common form of antibody that fight against the germs and prevents another repeat attack.

-Immunoglobulin M: These are the first line of defense when the body is exposed to a new germ before the Immunoglobulin G takes charge.

-Immunoglobulin E: These antibodies are generated as a reaction to allergens like pollen or certain foods and are tested when an allergy occurs.

What is the price of the IgE test in India?

The cost of the test varies depending on the number of allergens being tested and the center for testing. In general, the full range of allergen testing can cost around Rs. 4000 to 5000 while the test for a single allergen can cost around Rs. 300.

When will I get the test results?

The blood samples are processed by a machine and it may take a day or more to deliver the results, depending on the center.

What is the normal range for IgE?

The test results are generally reported in kilounits of antibody per liter (kU/L) or nanograms per milliliter (ng/mL). The upper limits of IgE in the blood vary from person to person and in general blood tests are usually considered positive if the allergen-specific IgE level is greater than 0.35 kU/L. But for certain airborne allergens, sensitivity can be indicated by values as low as 0.12 kU/L.

A positive or negative result needs to be interpreted by a doctor considering the patient’s condition, history, and risk factors.The chart indicates the normal IgE levels at various ages (Here IU/ml indicates International Units per Millilitre (IU/mL)):

What do the results mean?

IgE levels can be high when the body is fighting off an infection or in case there are some issues with the immune system. It can also be a result of any one of the ailments mentioned below.

– Allergies or chronic infections.
– Autoimmune disorders like rheumatoid arthritis, lupus, or celiac disease, resulting in an overactive immune system.
– Liver disease
– Inflammatory bowel disease.
– Malignancies or cancer, such as multiple myeloma, lymphoma, or leukemia.

The low levels of the protein indicate that the immune system is not functioning as it should in ideal conditions. This can be due to any of the following conditions.

– Effect of certain medicines, like steroids, on the immune system.
– Complications related to diabetes.
– Kidney related problems.
– An in-born weakened immune system or it being made weak by a condition like an HIV infection.

A high or low reading does not necessarily mean that you have one of these conditions. It is up to your doctor to accurately interpret the test results and suggest the next course of action.

Do I need to fast for the IgE test?

There is no fasting required for this test and a blood sample can be taken at any time during the day. For the best results, the sample should be collected several hours after a meal.

What else do I need to know before I test my IgE test

In some cases, the doctor may suggest other tests like full blood count (FBC) and white blood cell differential for an indirect diagnosis. There are also skin prick tests, patch tests and oral food challenges that can be suggested. At times, the doctor might alter your food by eliminating and reintroducing certain components, in order to locate the right allergen.

Is the IgE test safe during pregnancy?

There are no restrictions on pregnant women from undergoing an IgE test. Many pregnant women suffer from allergies like rhinitis, asthma, conjunctivitis, acute urticaria, anaphylaxis, food allergy, and drug allergy. The correct monitoring of these conditions is necessary for the health of the mother and the baby.

Is the IgE test safe for new-born babies?

A simple blood test or a skin prick testing in babies is a common and safe procedure for determining allergies.