Blood tests no ‘magic bullet’ for diagnosing allergies

Blood tests no ‘magic bullet’ for diagnosing allergiesWashington, Dec 26 : Blood tests and skin-prick testing should not be used as the only diagnostic strategies in allergy, a new study has suggested.

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 only on test results.

According to Sicherer and Wood say, these tests should be used only to confirm suspicion and never to look for allergies in an asymptomatic patient.

They added that 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.

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.

"Allergy tests can help a clinician in making a diagnosis but tests by themselves are not diagnostic magic bullets or foolproof predictors of clinical disease," Wood said.

"Many children with positive tests results do not have allergic symptoms and some children with negative test results have allergies," Wood added.

The study has been published in Pediatrics. (ANI)