Which lab studies are indicated in the workup of pediatric allergic rhinitis?

Updated: Jun 04, 2021
  • Author: Jack M Becker, MD; Chief Editor: Harumi Jyonouchi, MD  more...
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No studies are needed in allergic rhinitis (AR) if the patient has a straightforward history. When the history is confusing, various studies are helpful, including the following:

  • Skin-prick testing: This test is highly sensitive and specific for aeroallergens. However, a false positive reaction can occur without corresponding clinical features, especially when skin mast cells are easily activated by pressure or other physical stimuli.

  • Serum allergen-specific IgE testing: The main limitations are that patients may be sensitive on a molecular level before IgE response is clinically seen on standard skin testing. This may lead to positive results on laboratory tests that are not triggering clinical symptoms. A future advantage is that this may be a first step toward better customization of immunotherapy in the future. [7]

  • Nasal smear: Eosinophils usually indicate allergy. Neutrophils are more indicative of an infectious process, such as sinusitis. This is not used often anymore because of the difficulty in having the test performed. It was used commonly when office laboratories were common.

  • CBC count with differential: A CBC count may reveal an increased number of eosinophils. An eosinophil count within the reference range does not exclude AR; however, an elevated eosinophil count is suggestive of the diagnosis.

  • Immunoglobulin E (IgE): Serum IgE values are not routinely recommended to evaluate atopy. An IgE value within the reference range does not exclude AR; however, an elevated IgE value is suggestive of the diagnosis. Allergen-specific IgE testing, also known as radioallergosorbent test (RAST), which is a blood test that is no longer much in use, can be helpful if a specific allergen is suspected. Screening of a large number of allergens can cause confusion because of the possibility of false positives. This is especially true for IgE food allergy testing. The results of one explorative study found that low levels of serum IgE can be detected from age 6 months. The study suggests that detectable levels of IgE sensitization are associated with present symptoms of eczema, rhinitis, asthma, and food and inhalant allergens, and may also be predictive of future allergic symptoms. [8]

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