Component-resolved diagnosis

Component resolved diagnosis (CRD), also known as molecular allergy tests, involves testing to individual allergens in foods. This can be done either to individual allergens or to a large number of allergens on a microarray chip. This technology enables patterns of sensitisation to be seen, with the ability to test separately for both the heat labile and heat stable allergens in a food. For example, in an individual reporting reaction to peanuts, sensitisaiton to the major allergen Ara h 2 denotes a likely peanut allergy whereas sensitisation only to the PR10 allergen Ara h 8 indicates pollen-related food allergy. These tests are also very useful in those who are avoiding all nuts due to a suspected reaction to one nut, especially in pollen-sensitised individuals. Similarly, they may also be useful to assess for wheat allergy, by testing for the major allergen omega 5 gliadin in someone with positive tests to grass pollen. Also testing to ascertain whether someone with a positive test to house dust mite and shrimp is also positive to the major shrimp allergen tropomyosin Pen a 1. Resolving egg and milk allergy in older children and adults may also be indicated by negative tests to the major allergens Gal d 1 (egg) and Bos d 8 (milk). Microarray testing can be useful in problematic cases where the allergen is unknown, but due to often prolific sensitisation in older children and adults, testing for multiple allergens can make it difficult to interpret the results. The NICE evaluation of the test did not find sufficient evidence to recommend its routine use, but did consider it to be useful for difficult to evaluate cases.


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