This test measures the amount of immunoglobulin E (IgE total) in blood (under allergy diagnostics section on lab card).
IgE stands for immunoglobulin of class E. These antibodies are involved in the defense against parasites and in allergic reactions. An increased IgE is therefore seen in an allergic reaction or in an infection with parasites.
Immunoglobulins, or antibodies, are proteins produced by immune cells to clear foreign substances and fight infections (viruses, bacteria or parasites). There are five different types of immunoglobulins: IgG, IgM, IgA, IgD and IgE. IgE helps fight parasites such as worms, among other things. Sometimes the body's defenses kick in and IgE is made not only against invaders, but also against harmless substances, also called allergens, for example grass pollen or cat dander. A person can develop an allergy to such an allergen. There are two different IgE determinations: the total amount of IgE in the blood and the amount of IgE against a specific allergen, for example IgE against grass pollen.
The reference values for IgE are age-related; in adults the IgE level is higher than in children. Furthermore, the reference values depend on the measuring method used. A normal result means that an allergy caused by IgE is unlikely. Sometimes, however, a normal amount of IgE can be measured in someone, but there are allergic symptoms; further investigation is then usually necessary.
If the amount of IgE is increased this can fit in with the complaints of allergy, but it also happens that the complaints do not (at all) fit in with the increased IgE result. Therefore, the diagnosis of allergy can only be made on the basis of the complaints, possibly supplemented by the IgE result(s). A highly elevated result can fit hyper IgE syndrome and (job syndrome) or an IgE producing multiple myeloma (tumor Kahler's disease). In either case, an allergy must first be ruled out.