Friday, May 14, 2010

Are Food Allergies Over-Diagnosed?

Q&A with Wayne Shreffler, MD, PhD

A recent article in the New York Times (“Doubt is cast on many reports of food allergies”) brings important attention to a recently published study in the Journal of the American Medical Association on the way food allergies are currently diagnosed and treated.

The article, “Diagnosing and Managing Common Food Allergies,” is an analysis of the existing medical literature addressing the prevalence, diagnosis, and management or prevention of the most common food allergies (milk, egg, peanut, tree nuts, fish and shellfish). The authors’ primary conclusion is that the evidence for the prevalence and effective management of food allergy is undermined by a lack of uniform diagnostic criteria.

Wayne Shreffler, MD, PhD, is a pediatric allergist at MassGeneral Hospital for Children and director of the Food Allergy Center at Massachusetts General Hospital, whose research focuses on food allergy and asthma.

Q: Are food allergies over-diagnosed?

A: There is a well-known discrepancy between the percentage of people who believe they have a food allergy (as high as 30% in some surveys) and those who actually do (around 4%). Part of that discrepancy comes from people’s confusion about what is a food allergy versus other kinds of food intolerance. The second important point in the Times article, however, is that many people have evidence of an allergic kind of immune response – the presence of detectable allergic (IgE) antibodies – but are not clinically allergic. This often leads to misdiagnosis, confusion and unnecessary food eliminations.

Q: Should parents of children with food allergies or suspected food allergies do anything differently in light of this study?

A: I would not advise people to make any change to their child’s diet in light of this study – there is no new information presented in this study, it is a summary analysis of existing data that highlights areas in need of ongoing research. It is true that the presence of detectable IgE by itself is a poor predictor of food allergy, and because of this some people are needlessly avoiding foods on that basis alone; however, because some of these individuals are at risk for potentially severe reactions, testing should be interpreted, along with the history, by a physician who knows the field and can help determine the appropriate timing and setting of introducing foods like this.

Q: Should doctors change the way they treat food allergies?

A: While there are many questions that remain unanswered about the causes and best treatments of food allergies, the situation is not quite as bleak as is implied by the study authors’ statement that “food allergy has no universally accepted definition.” Universal agreement is rare in medicine generally, but with the combination of history taking, testing and food challenges – sometimes involving both an allergist and a gastroenterologist – a definitive diagnosis can almost always be made and the most effective, evidence-based treatment strategy pursued. Research is definitely needed to expand that evidence base and the treatments that we have to offer, and hopefully the kind of attention brought by the article, as well as ongoing support from the NIH and private groups, will help to spur that effort.

Q: Is there anything else we should know about the study?

A: One subtly of the JAMA report, not taken up in the Times piece, is the additional confusion among patients and generalists that comes from the fact that some types of food allergies are not consistently associated with detectable IgE (e.g., Eosinophilic Esophagitis and other gastrointestinal allergic diseases). Evaluation of patients for these conditions is more complicated by this fact and contributes to the lack of uniform diagnostic criteria. Better diagnostic methods and treatments for these diseases is an area of active research by many groups, including our own.

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