Immunoglobulin E Tests Not Always Reliable for Infants

Physicians are warned not to rely on allergen-specific immunoglobulin E (IgE) tests for pediatric allergies.

The mere detection of sensitization to an allergen on IgE tests is not always equivalent to a clinical diagnosis, cautioned a clinical report from the American Academy of Pediatrics (AAP).

The advisory from two allergists, Robert Wood of the Johns Hopkins Children's Center (Baltimore, MD, USA) and Scott Sicherer of Mt. Sinai Hospital (New York, NY, USA), urges clinicians to use caution when ordering allergy tests and to avoid making a diagnosis based solely on test results.

Most allergies result in the production of IgE antibodies that are specific to that allergen. A report, published in the January 2012 issue of Pediatrics, offers aid to pediatricians in selecting the appropriate allergy tests, and interpreting the results in the context of a patient history and clinical presentation.

The detailed medical history and tests must be interpreted in the presence of a clinical presentation, the authors noted. For instance, a child who eats eggs without any symptoms does not need to undergo testing for an egg allergy. The same holds true for pollen testing when a child is not physically exposed to a certain pollen.

In vitro allergen-specific immunoglobulin E (sIgE) testing is widely available to physicians, but the report sets out several caveats that physicians need to keep in mind when using these tests and before embarking on immunotherapy.

Both serum sIgE tests and skin-prick tests have similar diagnostic properties with specific pros and cons. Skin-prick tests offer immediate results and are low cost, but they require the availability of rash-free skin.

Serologic tests are not affected by antihistamines or extensive dermatitis, but require a blood sample and cost more.

The report also includes guidance on specific allergies: e.g., for asthma the physician is advised to follow national guidelines and test for indoor allergens (dust mites, mold). There is no current evidence that testing for total IgE will identify specific food allergies. In addition IgE tests are not relevant for many drug reactions. The diagnostic value of serum tests is not well characterized for latex allergies. A localized reaction at an insect bite or sting site does not indicate a risk for anaphylaxis; testing is not warranted.

In vitro allergen-specific immunoglobulin E (sIgE) testing is widely available to physicians, but the report sets out several caveats that physicians need to keep in mind when using these tests and before embarking on immunotherapy.

Related Links:
Johns Hopkins Children's Center
Mt. Sinai Hospital