Editor's Note: In December 2010, the National Institute of Allergy and Infectious Diseases (NIAID) released the comprehensive, up-to-date, evidence-based Guidelines for the Diagnosis and Management of Food Allergy in the United States. A coordinating committee composed of representatives from professional organizations, advocacy groups, and federal agencies presided over the development of the guidelines. Dr. Steven J. Czinn, Professor and Chair, Department of Pediatrics, University of Maryland School of Medicine in Baltimore, Maryland, represented the American College of Gastroenterology on this committee. Medscape spoke with Dr. Czinn about the practice implications of the food allergy guidelines when patients present with gastrointestinal signs and symptoms of possible food allergy.
Medscape: What aspects of the new NIAID allergy guidelines[1] are especially relevant to gastroenterology practice? What do they offer the gastroenterologist?
Dr. Czinn: The value of the new guidelines is that they provide an algorithm for the diagnosis and treatment of food allergy. The guidelines give us a working document that is clear, concise, and logical, and which can result in making a diagnosis or ruling out a diagnosis of food allergy. This document clarifies the landscape of food allergy, compartmentalizes the potential diagnosis, and puts forth a clear approach to the diagnosis and management of food allergy.
Medscape: Which allergic conditions manifest primarily with gastrointestinal symptoms? Which patients end up in a gastroenterologist's office?
Dr. Czinn: There is a significant amount of overlap between what we would see in a gastroenterologist's office vs an internist's or a pediatrician's office. We probably do see more in the way of food allergy coming to a pediatric gastroenterologist's office primarily because the kids or teenagers often present with symptoms of abdominal pain, difficulty swallowing, and even diarrhea.
Food allergies may present with a severe, life-threatening anaphylaxis -- gastrointestinal anaphylaxis -- or they can have a milder gastrointestinal component. We obtain the patient's medical history and perform a physical examination to try to determine the cause of the symptoms, and food allergy is definitely one diagnosis on the differential.
Medscape: What other tests would typically be done to rule out food allergy?
Dr. Czinn: If, after a thorough history and physical examination, food allergy was a serious consideration, a series of blood tests is available that can be very helpful. We would also measure immunoglobulin levels (serum IgE, specific for the food), particularly if there is a history of symptoms that occur consistently after eating a specific food. We would also work in conjunction with the allergist, so if we had real concerns about food allergy, we might consider referring the patient to an allergist for skin testing. The allergist, rather than the gastroenterologist, would more routinely conduct skin testing in these patients.
Medscape: What is the role of strategies such as elimination diets or open food challenges?
Dr. Czinn: Food challenges and elimination diets each have a place, particularly in the younger patient with a good history of symptoms associated with certain foods and positive blood tests (positive serum IgE test for the specific food). If proceeding with an elimination diet, we would recommend removing one food at a time from the child's diet to see whether that makes a difference in symptoms.
Food challenge is another useful strategy to rule out food allergy. If you have a strong suspicion but no definitive data, you might consider performing a food challenge. That strategy can be risky, however, because if the patient truly does have an allergic reaction, it could be severe, so food challenge should be conducted in an appropriate medical setting. Generally a food challenge can be used to confirm the diagnosis after we have made an initial diagnosis of food allergy. In addition, if we had some indication that perhaps the child or teenager had outgrown the food allergy, a food challenge would determine whether we can introduce small amounts of that food back into the patient's diet.
Medscape: How many patients complaining of adverse reactions to food have true food allergy?
Dr. Czinn: It's a difficult question to answer. It depends on how good the history is. If there is a very good history of symptoms that occur after eating a specific food, the likelihood is high that the patient has a true food allergy. A condition called eosinophilic esophagitis (EoE) falls into this category. Complaints such as dysphagia, food "getting stuck," or difficulty swallowing increase the likelihood of making the diagnosis. EoE is being diagnosed fairly frequently these days. If the history is good, it is more likely that EoE is the correct diagnosis.
Medscape: Is the prevalence of non-IgE-mediated food-induced allergic disorders such as EoE increasing?
Dr. Czinn: EoE is probably just being diagnosed more because it is now recognized as a cause of certain symptoms. However, to make a definitive diagnosis of EoE, the esophagus must be biopsied. The esophagus can be normal, visually, but you must take a biopsy sample and look specifically at the lining of the esophagus under the microscope for a type of blood cell called an eosinophil. Biopsy of the esophagus wasn't routine a few years ago. Most likely, our index of suspicion is higher, so we are doing more biopsies and diagnosing EoE more frequently.
This is an evolving field. Eosinophils can be found in other areas of the gastrointestinal tract, indicating other conditions that have slightly different names, such as eosinophilic gastroenteritis. Large numbers of eosinophils found anywhere in the gastrointestinal tract are probably an indication of some sort of allergy, primarily food allergy.
Medscape: Are these disorders all distinct or are they part of a single syndrome?
Dr. Czinn: These disorders may be part of a continuum, but the treatments are somewhat different, and the conditions are found in different populations. For instance, allergic colitis is primarily a diagnosis in infants and children, characterized by an allergy or intolerance to formula, resulting in bloody diarrhea. So that condition is seen primarily in the younger patient. These conditions are all related to some extent, perhaps on the same continuum, but are slightly different conditions occurring with different frequencies in different age groups.
The first step in managing any of these conditions is to try to identify a dietary antigen that can be removed from the diet. If that's not successful, other treatments can be initiated.
Medscape: Where does celiac disease fit in?
Dr. Czinn: Celiac disease is a related condition but it is not immune mediated in the same manner as food allergy. Celiac disease is mediated by the immune system but it is not an allergy in the true sense of the word. It is intolerance to gluten, a component of wheat. Although the treatment is the same (removing gluten), it is not an IgE-mediated allergic response. It is actually a toxic response rather than an allergic response.
Medscape: Under what circumstances is endoscopy indicated to diagnose food allergy or other conditions? How do these findings influence the diagnosis?
Dr. Czinn: Endoscopy has a role in the diagnosis of the constellation of signs and symptoms that may be the result of a food allergy. The symptoms of food allergy have tremendous overlap with the symptoms of celiac disease, Crohn disease, and gastritis. A diagnostic endoscopy sometimes is very useful to pin down the diagnosis. If large numbers of eosinophils are seen in the esophagus, the diagnosis would be EoE. If ulcers are seen in the stomach, the diagnosis is gastritis or ulcers. You might see histologic signs of Crohn disease. Celiac disease requires an endoscopy as well for the diagnosis. In celiac disease, you would see blunting of the villi in the small intestine. So endoscopy plays a major role in allowing us to make the diagnosis in patients who have the signs and symptoms that might ultimately be food allergy.
Medscape Allergy & Immunology © 2011 WebMD, LLC
Cite this: Laura A. Stokowski. Food Allergy: The Gastroenterologist's Perspective - Medscape - Apr 20, 2011.
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