Although the exact prevalence of food allergy in the United States is not known, it is estimated that 10-12 million Americans are affected. To address this growing public health problem, the National Institute of Allergy and Infectious Diseases (NIAID) in conjunction with professional organizations including the American Academy of Allergy, Asthma & Immunology (AAAAI), federal agencies, and patient advocacy groups worked together to develop clinical guidelines for healthcare professionals on the diagnosis and management of food allergy. The Guidelines for the Diagnosis and Management of Food Allergy in the United States were released in December 2010. At the AAAAI 2011 meeting, Medscape taped this discussion between Matthew J. Fenton, PhD, from NIAID, and Hugh A. Sampson, MD, past president of AAAAI, both of whom were involved in the guideline development process.
Dr. Fenton: Hello. My name is Dr. Matthew Fenton. I'm Chief of the Asthma, Allergy, and Inflammation Branch at NIAID. I led the Institute's effort to create clinical guidelines for the diagnosis and management of food allergy.
Here with me today is my colleague Dr. Hugh Sampson, Professor of Pediatrics and Dean for Translational Biomedical Sciences at the Mount Sinai School of Medicine in New York City where he serves as the Director of the Jaffe Food Allergy Institute. Dr. Sampson is past president of AAAAI. Dr. Sampson made the food allergy guidelines one of his presidential initiatives, and he chaired an expert panel writing group and served on the guidelines coordinating committee.
The food allergy guidelines were released in December 2010; with their release how should they now guide clinical practice? That's the topic we're going to discuss today for Medscape Allergy & Clinical Immunology.
Although the exact prevalence of food allergy in the United States is not known, it's estimated that 10-12 million Americans are affected. A number of different diseases with similar symptoms are shared with food allergy, so there is a real potential for overdiagnosis of food allergy. Current increases in the prevalence of food allergy match the increases in prevalence that we see with other allergic diseases such as asthma. Hugh?
Dr. Sampson: Yes. Many food allergies are also outgrown as children get older. Several food allergies such as milk, eggs, wheat, and soy are outgrown in about 80% of the cases, whereas allergies to other foods such as peanuts, tree nuts, fish, and shellfish are typically not outgrown. Only about 20% of children will outgrow allergies to these foods.
Of interest, when individuals develop food allergy as adults those allergies also tend to be very persistent.
Dr. Fenton: Sensitization to food is not the same thing as clinical food allergy. That's a key point that the guidelines bring up. In the case of allergic sensitization, an individual who is sensitized may not go on to proceed to clinical disease. In the case of people with multiple allergen sensitivities, only one of those allergens may be responsible for the symptoms of food allergy, and that's one of the challenges in diagnosis -- to identify the particular allergen in multisensitized patients.
The guidelines provide a consensus definition for food allergy: one of the major goals of the initiative. They also provide best clinical practice recommendations. The key here is to provide recommendations for healthcare professionals across a variety of specialties ranging from allergists to dermatologists and pulmonologists all the way to family practice specialists and rural healthcare providers.
Dr. Sampson: Right. The guidelines were created by a variety of experts, so we really have good opinions from all the different areas.
With respect to how to diagnose food allergy, all of the appropriate methods were carefully reviewed. History and physical exam are believed to be very good for helping direct the evaluation of food allergy, but history alone is not adequate to make the diagnosis. Many allergists will do tests such as the skin prick, which is very good for helping identify potential foods that could be causing the problem, but by themselves these tests are not adequate. There are also in vitro tests such as serum IgE [immunoglobulinE] levels to different foods. Those can be also quite useful in identifying potential sources of the allergy, but by themselves are really not adequate to make the diagnosis.
The writing panel believed that the elimination diet was potentially useful for helping make the diagnosis, especially with some of the non-IgE-mediated type of allergies, but the only direct way to make the diagnosis is with the oral food challenge. The committee believed that the double-blind, placebo-controlled food challenge is the gold standard for making such a diagnosis. However, they also believed that the open food challenge or the single-blind challenge could be diagnostic if the challenge was negative or if the symptoms that were provoked by the challenge looked the same as what was described in the history and were supported by laboratory studies.
The writing group also looked at a number of other tests that are potentially used such as IgG levels, IgG4 levels to foods, and several others and believed that no other tests were really of value.
The group also looked at recommendations for proper treatment of food allergies, and that starts with the appropriate diagnosis. Once the specific food allergy is diagnosed, then avoidance diets are recommended. At this point in time, avoidance is the only effective way to treat a food allergy. There has been a lot of excitement about oral immunotherapy and sublingual immunotherapy, but at this point in time it was believed that that information is inadequate to support these measures as forms of therapy going forward.
They also reviewed potential medications that people might use to try to prevent food allergic reactions and basically came to the conclusion that no medications can be used to prevent either the IgE-mediated or the non-IgE-mediated food allergy.
Finally, they believed that in children it was really necessary to have nutritional evaluations done on a periodic basis as well as weight checks, especially in children who are on very restrictive diets. Going forward, because many food allergies are outgrown (depending on the food) these children should be re-evaluated on a regular basis.
Recommendations were made about trying to prevent food allergy, and there has been a lot of discussion about whether we can actually prevent it. The guidelines assert that there is no reason for mothers to be eliminating foods either during pregnancy or during breast-feeding in an attempt to prevent food allergy. The information out there just does not support that as a potential way to prevent allergy. The committee does recommend breast-feeding for the first 4-6 months of life, but the literature doesn't suggest any reason to avoid any particular foods -- even allergenic foods -- beyond that 4- to 6-month period.
Some people have also tried to avoid allergy by avoiding cross-reacting foods. For example, somebody who is allergic to milk may have a positive skin test for something like beef, but it's very unlikely that beef would also be a cause of food allergy. The idea of trying to avoid foods by association was not recommended.
Several recommendations were made about treatment of anaphylaxis. The main thing was that children or adults with food allergies should be cared for by physicians who are familiar with anaphylactic reactions, types of symptoms, and timing; and that rapid treatment was necessary and the use of intramuscular epinephrine was really the treatment of choice. If the individual has a reaction, it's recommended that the patient be observed for about 4-6 hours afterward because a biphasic reaction can occur even after the patient looks to be well along the way to recovery.
It was believed to be very important to educate patients about recognizing early signs of anaphylaxis, how to avoid the offending foods, and prior to discharge making sure that they have a prescription for some form of injectable epinephrine as well as a follow-up appointment with their physician to get an appropriate evaluation of their food allergies.
Dr. Fenton: The recommendations in the guidelines are evidence based, but the expert clinical opinion by the writing groups was key in making the final wording of the recommendation especially in cases in which the evidence was weak. In preparing the evidence report, more than 12,000 papers were evaluated for inclusion in the evidence report. Each guideline describes the strength of the evidence that was used in making the guideline recommendation in addition to the contribution that was made by expert clinical opinion.
Each chapter of the guidelines concluded with a section on knowledge gaps. That points out future directions for research efforts on the basis of the paucity of knowledge in these particular areas. As the major funding agency for food allergy research in the United States, these knowledge gaps will guide the NIAID in developing new research funding opportunities.
Dr. Sampson: The guidelines don't present radically new information, but they do evaluate, in a very thorough fashion, all the literature that is out there and come up with recommendations as well as point out some common mistakes that are made by physicians.
For example, one thing that was stressed in the section on therapeutics was the tendency to use antihistamines first in treatment of an anaphylactic reaction, and so the guidelines stress that epinephrine given intramuscularly is the treatment of choice for anaphylaxis.
Also, many physicians have a tendency to take the results of skin tests or serum IgE levels and then tell patients that they are allergic to that particular food. As you pointed out when we first started talking, these tests tell us that the patient is sensitized but do not necessarily tell us that the patient is going to have clinical symptoms.
The guidelines also stress the issue of mothers trying to avoid particular allergens while they're pregnant or breast-feeding. As pointed out by the American Academy of Pediatrics guidelines about a year ago, the evidence is insufficient to support that approach as a way to try to prevent their offspring from having particular food allergies.
Dr. Fenton: In addition to the guidelines, the NIAID created multiple resources for healthcare professionals, patients, and families. These resources include a summary version of the guidelines that highlight the guidelines but don't go into all of the details behind the rationale that supports those guidelines.
Also, we've just generated a patient- and family-friendly synopsis of the guidelines that patients and their families can use to educate themselves prior to visiting the physician, and help them better understand how the physician will go about treating and managing the disease.
These resources are freely and publicly available from the NIAID Website.
Thank you for joining us today. This is Dr. Matthew Fenton with Dr. Hugh Sampson for Medscape Allergy & Clinical Immunology.