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Allergies? You Might Want to Confirm

January 4, 2012


If your child has allergies or you suspect they might, you should consider this insightful article about allergy testing that came out in the January issue of Pediatrics: Robert Wood of the Johns Hopkins Children’s Center and Scott Sicherer of Mt. Sinai Hospital in New York, warn that blood tests and skin-prick testing are not enough to diagnose allergies on their own. Instead, they argue, these diagnostic tests should be used to confirm an allergy. According to an article Johns Hopkins put out last week, Wood says. “Many children with positive tests results do not have allergic symptoms and some children with negative test results have allergies.”

The JH article goes on to say: “Test results….., should be interpreted in the context of a patient’s symptoms and medical history. If a food allergy is suspected, Sicherer and Wood advise, the patient should undergo a food challenge — the gold standard for diagnosis — which involves consuming small doses of the suspected allergen under medical supervision.

Blood tests and skin-prick testing “can tell whether someone is sensitive to a particular substance but cannot reliably predict if a patient will have an actual allergic reaction, nor can they foretell how severe the reaction might be… Many people who have positive skin tests or measurably elevated IgE antibodies do not have allergies, they caution.”

I found this particularly interesting from their research: “Screening panels of food allergens without previous consideration of the history is not recommended, because sensitization without clinical allergy is common. For example, ∼8% have positive test results for peanut, but ∼1% are clinically allergic.16

Another note of caution: Commercial tests vary in sensitivity and labs may interpret tests results differently.

The researchers helpful summary lays out what they found:

  1. Treatment decisions for infants and children with allergy should be made on the basis of history and, when appropriate, identified through directed serum sIgE or SPT testing. Newer in vitro sIgE tests have supplanted radioallergosorbent tests.

  2. Allergy tests for sIgE must be selected and interpreted in the context of a clinical presentation; test relevance may vary according to the patient’s age, allergen exposure, and performance characteristics of the test.

  3. Positive sIgE test results indicate sensitization, but are not equivalent to clinical allergy. Large panels of indiscriminately performed screening tests may, therefore, provide misleading information.

  4. Tests for sIgE may be influenced by cross-reactive proteins that may or may not have clinical relevance to disease.

  5. Increasingly higher levels of sIgE (higher concentrations on serum tests or SPT wheal size) generally correlate with an increased risk of clinical allergy.

  6. sIgE test results typically do not reflect the severity of allergies.

  7. Use of a multiallergen serum test can be helpful for screening for atopic disease if there is a clinical suspicion. If positive, allergen-specific testing may be considered.

  8. Tests for allergen-specific IgG antibodies are not helpful for diagnosing allergies.

  9. Because test limitations often warrant additional evaluation to confirm the role of specific allergens, consultation with a board-certified allergist-immunologist should be considered.

We have a list of allergist in NYC on our Marketplace- check them out here.