Immunoglobulin E (IgE), total, serum

The Immunoglobulin E (IgE), total, serum test is used to assess allergic disease, track response to therapy, and serve as a screening marker of atopy when clinically appropriate. Measurement of Total IgE (IgE, total) also aids the differential diagnosis when helminthic infestation is suspected and contributes to evaluation of selected immunopathologic conditions, including consideration of IgE myeloma. In children, higher total IgE can help estimate short‑term risk for development of allergic disease. This measurement does not substitute for allergen‑specific IgE testing when identification of causal allergens is required.

Immunoglobulins are gamma globulins synthesized by B lymphocytes and composed of two heavy and two light chains joined by disulfide bonds. IgE, historically termed reaginic antibody, binds with high affinity to mast cells and basophils in the skin and mucosal tissues. Cross‑linking of surface‑bound IgE by allergen triggers degranulation with release of vasoactive mediators, including histamine, serotonin, and heparin, producing the clinical manifestations of type I hypersensitivity such as asthma, rhinitis, urticaria, and atopic dermatitis. Total IgE is frequently increased in individuals with atopy, and higher levels in children correlate with a greater short‑term likelihood of developing allergic disease. IgE also participates in antiparasitic immunity (eg, to Ascaris, Toxoplasma, nematodes, Echinococcus, Trichinella), and marked elevation may reflect helminthic infection. While total IgE functions as a screening marker, determining the responsible allergen requires measurement of allergen‑specific IgE.