Immunoglobulin E (IgE): indications, normal values ​​and results

Immunoglobulin E (IgE): indications, normal values ​​and results

Immunoglobulin E are antibodies produced by white blood cells in the event of an allergic reaction. The IgE dosage is prescribed to look for a general allergic background or a specific allergy. Explanations with Dr François Blanchecotte, medical biologist, President of the Union of Biologists.

What is immunoglobulin E (IgE) and what is its role?

Immunoglobulins are blood proteins produced by white blood cells to protect the body against bacteria, viruses and other toxins. Immunoglobulin E (IgE) are antibodies produced by B lymphocytes (a type of white blood cell) in response to an allergen. “IgE is synthesized in the body by cells (B lymphocytes) which will defend us against the allergen. They will form a conglomerate with the allergen, which will cause an immune response and trigger hormonal and other responses Cascade. It is a system that is triggered in the event of hypersensitivity to an allergen.. This hypersensitivity reaction is most often instantaneous, more rarely it can be delayed over time. comments François Blanchecotte, medical biologist.

Total IgE and specific IgE: what are the differences?

There are two types of serum IgE: total IgE which indicates a general allergic background and specific IgE which is sought in cases of atopic diseases or parasitic infections.

High IgE level: what is hyper IgE syndrome?

Hyper-IgE syndrome is a rare congenital immune deficiency characterized by the appearance of recurrent abscesses, severe skin rash, and sinus and lung infections.

Why measure IgE?

“Total and specific IgE are essentially requested in the event of suspected allergies since they will be developed in the event of an allergy, particularly in children, informs the medical biologist. As soon as we come into contact with an allergen (for example pollen, dust, mites, animals, flowers, trees), we develop IGE. This dosage makes it possible to assess the overall allergic rate of an individual but has no diagnostic value, it is less and less in demand.

IgE dosage: why is the rate increasing? What rate indicates an allergy?

To be considered normal, the level of total IgE in the blood must be less than 150 IU/ml (International Units per milliliter). Beyond this value, an allergy is suspected. The determination of total IgE is often carried out as first line, in subjects who have levels greater than 1000 international units per liter of serum. “We think the person has a strong allergy but we don’t know what, so this test only gives an indication of the body’s overall reaction.” nuances the specialist.

Immunoglobulin E: how is the examination carried out?

The IgE assay is carried out by examining a blood sample. The blood test is taken at the elbow crease and does not require fasting.

What results can we expect from an IgE analysis?

The IgE assay has no major diagnostic value. It is essentially a sorting test to confirm a general allergic background or a specific allergy (pollen, mites, dust, etc.).

The prick test, the examination of choice to assess an allergy

“From now on, the preferred test when a subject presents symptoms of allergy is the prick test. This skin test makes it possible to assess hypersensitivity to certain allergens”, says François Blanchecotte. The allergist injects the different allergens subcutaneously in order to penetrate the allergen into the epidermis. In case of allergy, swelling, redness and itching appear within a few minutes.

How to manage IgE-related allergies?

IgE-related allergies cause classic allergy symptoms, namely: sneezing, runny nose, watery eyes, coughing, etc. Symptoms of a food allergy generally appear within two hours of ingesting the allergenic food. . In addition to the symptoms mentioned above, skin reactions (eczema, hives) and digestive problems (nausea, vomiting) can be added. In the most severe cases, angioedema (sudden swelling of the skin and mucous membranes of the head and neck) may occur.

The management of IgE-related allergies is based on three pillars:

  • Avoidance of the allergen: By avoiding coming into contact with the allergen, allergy symptoms are relieved. They can even disappear;
  • Symptomatic drug treatment: it is essentially based on the prescription of antihistamines. Local treatment such as eye drops or nasal spray may also be offered. In the event of anaphylactic shock, an intramuscular injection of adrenaline is necessary;
  • Desensitization: this is considered in the event of failure of eviction and symptomatic treatment. Desensitization consists of administering a small quantity of allergen to the body on a regular basis in order to gradually accustom it to it.