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Sunday, July 23, 2006

Study May Lead to Better Food Allergy Test

Here's major news for those who might be suffering from dairy allergies.

Allergy testing today is difficult and invasive. Some tests don't work very well, leading to false positives – those who are told they have an allergy when they don't – and false negatives – those who are told they don't have an allergy when they do. And skin pricks and food challenges are uncomfortable at best.

Amazingly, a test that involves no more than identifying a protein from stool samples may be possible, according to a paper that was published in the July 2006 issue of the medical journal Gastroenterology.

The paper was published under the ungainly title of "Transcytosis of IgE–Antigen Complexes by CD23a in Human Intestinal Epithelial Cells and Its Role in Food Allergy," by Hongxing Li, Anna Nowak–Wegrzyn, Zachary Charlop–Powers, Wayne Shreffler, Mirna Chehade, Sunil Thomas, Giulia Roda, Stephanie Dahan, Kirk Sperber, and M. Cecilia Berin.

A translation for the jargon-challenged can be found at MedicalNewsToday.com.

Food allergies often present a unique problem for allergy testing since not every patient has detectable levels of immunoglobulin E (IgE) in their serum, especially patients with delayed allergies. A number of reliable testing methods exist for food and other allergies, including skin tests and serum IgE tests, however, they may not accurately diagnose food allergies. The oral food challenge is considered the most accurate test for food allergies but is expensive to administer and has to be done in a controlled environment. Immunoglobulin (antibody) E is a protein produced by plasma cells (or B-Cells , a type of lymphocyte ), which is designed to control the immune response in extracellular fluids by binding to substances in the body that are recognized as foreign.

The study, conducted at the Mount Sinai School of Medicine, New York, showed for the first time that CD23, a protein normally expressed in a person's intestinal tract, acts as a receptor for IgE, a protein associated with allergic reactions, and enables it to participate in food-allergic reactions.

"We believe that the presence of CD23 may provide a surrogate method of looking at the gut without invasive tests like biopsies," according to M. Cecilia Berin, PhD, assistant professor, pediatrics/allergy and immunology, Mount Sinai and lead author of the study….

Researchers collected stool samples from nine pediatric patients (age range three to 17 years) who underwent an oral food challenge, during which they were administered either egg or milk in a controlled environment. All patients had a history of allergies to these foods and had reacted positively through other testing methods. Their symptoms, which occurred less than two hours after the food challenge, included skin reactions, breathing problems and gastrointestinal problems or a combination. They were matched to five pediatric controls with no food allergies.


It was a small scale study of just a few young patients, so the results are extremely preliminary, but they are promising.

Better tests have been needed for years, but allergies are so tricky and manifest in so many different ways that a general test has always been out of reach. Whether that's truly changed or whether this is an unfortunately blind alley will take several more years of testing. If it does work, however, it'll be the best news in the allergy field for some time.

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