Food Allergy Testing Methods
An allergy is an inappropriate response by the body's immune system to a substance that is not normally harmful (Balch 2006). Food Allergies occurs when a person's immune system generates an antibody response to the ingested food (Balch 2006). In 2012, 5.6% or 4.1 million children reported food allergies in the past 12 months (Bloom, Cohen & Freeman 2011). In order to see what appropriate treatment is helpful for a person who has food allergies it is important to start using different food allergies testing methods. The different food allergy testing methods are the elimination/challenge, skin prick testing, atopy patch test, radioallergosorbent testing, enzyme-link immunosorbent assay, third generation ELISA Assays microarray chip technology and Energetic Methods (Pizzorno & Murray 2013). There are other testing methods that have been used for food sensitivity testing and treatment but systematic scientific studies have either not been done to verify the clinical relevance of these methods, or have shown the tests to be unreliable and clinically questionable (Pizzorno & Murray 2013).
Elimination/Challenge otherwise called the Oral Food Challenges is used to identify and verify food reactions by eliminating a suspect food for a period of time to see which symptoms subsides (Pizzorno & Murray 2013). When the food is reintroduced to the diet, the clinicians observe which symptoms reappear (Pizzorno & Murray 2013). This is known as the gold standard for diagnosing food allergies. Doing this method can motivate food elimination compliance. It is very adaptable and does assist with a wide range of people. The Elimination/Challenge method is a time consuming and it requires for persons to stay on a particular restrictive diet plan. For persons who have severe food allergies this type of method is not recommended.
Skin prick testing (SPT) is the most common testing performed to detect the presence of allergen-specific IgE to foods, environmental allergens, antibiotics latex and some venoms (Robinson & Smart 2008). It is performed on the skin of either the back or the forearm in older patients. A small drop of commercially prepared allergen is placed on the skin and the person who is allergic to the allergen would have a great swelling reaction than that of the control (Pizzorno & Murray 2013). Some of the advantages of the skin prick testing are that it is more sensitive and specific than the radioallergosorbent testing (RAST) and it is very accurate for identifying environmental allergies. SPT however positive skin test may need to be confirmed by a positive reaction by conducting an elimination/challenge testing method. SPT gives only <50% overall positive predictive accuracy with a suspected food allergy (Robinson & Smart 2008). If the skin prick test result is ambiguous with the clinical history of the client then the test should be repeated with fresh food if possible or with a RAST.
Atopy patch test (APT) is used to identify allergies that take a few days to show up and it is also known as late-phase clinical reactions (Pizzorno & Murray 2013). It is commonly used to distinguish irritant contact dermatitis from allergic contact dermatitis. APT uses adhesive tape to adhere particular potential allergens on the skin like the Skin Prick Testing (Pizzorno & Murray 2013). It offers a way to look at T-cell mediated reactions to foods but doing this testing can be time-consuming and interpretation the results is more challenging. A controlled, elimination/ challenge testing is still necessary to verify symptoms in reactive foods (Pizzorno & Murray 2013).
Radioallergosorbent testing (RAST) detects free antigen IgE in the serum and it can be used to diagnose all types of allergy. RAST testing is performed using human serum to measure the amount of IgE antibodies present (Pizzorno & Murray 2013). This type of testing allows for identification of allergens in the blood rather than using an SPT. RAST specifically looks at only IgE antibodies and is hampered by cross-reactive proteins and low-quality test agents (Pizzorno & Murray 2013). The use of allergen mixtures (eg. food mix) for RAST is not recommended (Robinson & Smart 2008).
Enzyme-link immunosorbent assay (ELISA) is similar to RAST in that an antigen (allergen) is bound to a solid substrate and serum or whole blood is added to allow for antibodies to bind to the allergen being tested (Pizzorno & Murray 2013). ELISA testing is versatile, relatively inexpensive, and readily available, making it a useful tool for food allergies. The problem with this testing is that a person must be eating the food in question for it to come up positive on antibody test. Without exposure to the food, the white blood cells do not get activated and make antibodies (Pizzorno & Murray 2013). ELISA tests for IgG or IgA antibodies are often used by alternative medicine practitioners to identify food allergies that have not been identified with more conventional, but limited, methods examining IgE antibiotics (Pizzorno & Murray 2013).
The third generation ELISA Assays is a similar method to RAST and ELISA testing but it uses an automated machine and different solid substrates to increase sensitivity and specificity. It is more expensive and generally only available for IgE antibodies (Pizzorno & Murray 2013). Third generation ELISA Assays test improved on RAST by developing a dose-response curve of IgE. For identifying specific IgE allergens, those methods are less sensitive than skin testing but more sensitive and specific than ELISA testing. This system is more sensitive and specific for IgE antibody tests than ELISA or RAST (Pizzorno & Murray 2013).
Microarray chip technology is am IgE antibody technology that utilizes serum to identify IgE antibodies. It is being utilized to identify proteins in foods that a person reacts to (Pizzorno & Murray 2013). Microarray tests are not considered as sensitive as the third generation ELISA tests when the same allergens are used (Pizzorno & Murray 2013).
Energetic Methods is food sensitivity testing measure the energetic responses to food or other substances, such as medications, supplements, and hormones. The problem is that the energetic methods testing for diagnosis and treatment of food sensitivities is not reliable and not supported in the literature (Pizzorno & Murray 2013).
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Balch, P. (2006). Allergies. Prescription for Nutritional Healing,, 4th ed. (pp.177-183), New York,: NY: Avery.
Bloom, B., Cohen, R. & Freeman G. (2011) Summary health statistics for U.S. children: National Health Interview Survey, 2010. National Center for Health Statistics. Vital Health Stat 10 (250).
Lieberman, J. & Sicherer, S. (2011) Diagnosis of Food Allergy: Epicutaneous Skin Tests, In Vitro Tests, and Oral Food Challenge, Current Allergy Asthma Rep, 11:58–64, DOI 10.1007/s11882-010-0149-4
Pizzorno, J. & Murray, M. (2013). Food Allergies. Textbook of Natural Medicine, 4th ed. (pp.133-139), St. Louis: MO: Elsevier
Robinson, M. & Smart, J. (Apr 2008). Allergy testing and referral in children. Australian Family Physician. 37 (4) pp. 210-3. http://search.proquest.com/docview/216294518?accountid=158302