Immunoglobulin E (IgE)

Definition

• IgE mediates allergic and hypersensitivity reactions. There is a significant overlap in total IgE between allergic and nonallergic individuals. Measurement of total IgE is not very useful as a standalone screen for allergy disease.
• Normal values: see Table 16.42.

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TABLE 16 " “42Normal Values for IgE by AgeView LargeTABLE 16 " “42Normal Values for IgE by Age Age (y) Value (kU/L) 0 " “2 <53 2 <93 3 <120 4 <160 5 <192 6 <224 7 <248 8 <260 9 <304 10 <328 18 <127

Use

• For allergy testing; IgE antibodies and skin tests are essentially interchangeable.
• Indicates various parasitic diseases.
• Diagnosis of E-myeloma.
• Diagnosis of bronchopulmonary aspergillosis; a normal serum IgE level excludes the diagnosis.

Interpretation

Increased In

• Atopic diseases Exogenous asthma in approximately 60% of patients Hay fever in approximately 30% of patients Atopic eczema
• Influenced by type of allergen, duration of stimulation, presence of symptoms, and hyposensitization treatment
• Parasitic diseases (e.g., ascariasis, visceral larva migrans, hookworm disease, schistosomiasis, Echinococcus infestation)
• Monoclonal IgE myeloma

Decreased In

• Hereditary deficiencies
• Acquired immunodeficiency
• Ataxia " “telangiectasia
• Non-IgE myeloma

Normal In

Limitations

• A normal level of IgE in serum does not eliminate the possibility of allergic disease.