Peanut Allergies Misdiagnosed
False positives common on peanut allergy tests
A recent Swedish study has shown that 2 out of 3 children diagnosed with peanut allergy may not be allergic to peanuts at all. They may in fact have a much less serious allergy to birch pollen, which will come as welcome news to many families living in fear of peanuts.
"There are several different proteins in peanut that can give rise to allergic reactions," says Dr. Magnus Wickman. It turns out that one of these proteins is very similar to an allergy-producing protein in birch pollen. As a result, patients allergic to birch pollen may experience a mild reaction to peanuts as well, but not a life-threatening one. The problem is that standard allergy tests are unable to distinguish between these two allergies, resulting in false positives for peanut allergy.
Today's routine allergy tests use an extract of a potential allergen to test either for an allergic reaction or for the presence of antibodies. If an allergy test is positive, there is no way of knowing what specific proteins in the extract the patient is allergic to. Dr Wickman and his team work in the field of molecular allergy, developing allergy diagnostics that can identify more precisely the cause of allergic reactions.
The BAMSE project is a 10-year study of 4,000 children, jointly conducted by the Karolinska Institutet in Sweden, and Phadia, a manufacturer of allergy tests. Together they have developed new ImmunoCAP allergy tests which can reveal what specific proteins in an allergenic substance a patient is allergic to.
ImmunoCAP Allergen Component tests are widely available in Europe, but they have not yet been approved by the FDA for common use in the United States. In the meantime, allergy specialists in the U.S. may use these new tests as a Laboratory Developed Test only.
April 13, 2010