An advisory from two leading allergists, Robert Wood of the Johns Hopkins Children's Center and Scott Sicherer of Mt. Sinai Hospital in New York, urges clinicians to use caution when ordering allergy tests and to avoid making a diagnosis based solely on test results.
In an article, published in the January issue of Pediatrics, the researchers warn that blood tests, an increasingly popular diagnostic tool in recent years, and skin-prick testing, an older weapon in the allergist's arsenal, should never be used as standalone diagnostic strategies. These tests, Sicherer and Wood say, should be used only to confirm suspicion and never to look for allergies in an asymptomatic patient.
Test results, they add, 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.
Unlike food challenges, which directly measure an actual allergic reaction, skin tests and blood tests are proxies that detect the presence of IgE antibodies, immune-system chemicals released in response to allergens. Skin testing involves pricking the skin with small amounts of an allergen and observing if and how the skin reacts. A large hive-like wheal at the injection site signals that the patient's immune system has created antibodies to the allergen. Blood tests, on the other hand, measure the levels of specific IgE antibodies circulating in the blood.
These tests 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, the scientists say. Many people who have positive skin tests or measurably elevated IgE antibodies do not have allergies, they caution. For example, p
|Contact: Ekaterina Pesheva|
Johns Hopkins Medical Institutions