Specific Inhalant Allergy Tests
Posted by Health articles on June 3rd, 2009
Laboratory confirmation of the presence of IgE antibodies to specific allergens such as dust mites, pollens, or animals is very helpful in establishing a specific allergic diagnosis, especially if the history of exposure to a specific allergen is not clear-cut. It may be necessary to test for specific allergens to convince the family and patient of an allergic diagnosis and to reinforce the importance of environmental control.
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Although skin testing might be performed in any child at any age, children less than 1 year of age may not mount a positive reaction. Often, the child who has seasonal respiratory allergy will not manifest a positive test until after two seasons of exposure. Clinicians should use allergens for skin testing selectively and employ only common allergens of potential clinical importance. The most useful allergens for which to test in the child who has perennial inhalant allergy are house dust mites (Dermatophygoides), animal danders, and fungi (molds) (Table 2). Allergens important in the diagnosis of seasonal allergic rhinitis are weeds, grasses, and tree pollens. These allergens vary not only by season of year but by geographic distribution. Therefore, allergens used for skin testing must be individualized and should be selected on the basis of prevalence in the local area and the home and school environment.
IgE antibody can be tested via two methods: in vivo skin testing and in vitro serum testing (Table 3). Their advantages and disadvantages are outlined in Table 4. For most patients, skin tests that are performed properly offer the best available method for detecting the presence of allergen-specific IgE. The prick, also called the puncture or epicutaneous skin test, is preferred; scratch testing has been abandoned as too traumatic. If prick tests are negative and allergy is highly suspect, then intradermal testing, which is more sensitive, may be employed. Skin tests are both 10% to 20% more sensitive and less expensive on a per test basis than are in vitro serum tests.
Tags: allergic diseases, Allergies, allergy, allergy tests, IgE antibody