Peanut allergy diagnosis and management: the role of allergen components

Abstract

Peanut and soy are both legumes and therefore phylogenetically related. Both peanut and soy should be addressed in the diagnostic work-up of a suspected allergy to either of these foods because of possible cross-reactivity. Allergic symptoms to both foods can range from mild oral allergy symptoms to severe respiratory or even cardiovascular symptoms. Therefore, it is important that peanut or soy allergy is not missed in the diagnostic procedure and an adequate elimination diet is prescribed. An incorrect diagnosis of food allergy on the other hand significantly impairs the quality of life and increases the risk of impaired growth and inadequate nutrient intake in case of children. Skin prick test (SPT) and IgE reactivity to peanut extract in serum are two methods that are generally used to measure sensitization. Since sensitization is often not related to clinical symptoms, test results can be ‘false-positive’ when used as a diagnostic test for peanut or soy allergy. The reference standard on the other hand, a double-blind, placebo-controlled food challenge, has many disadvantages: it is time-consuming, has high costs, is stressful for the patient, might result in severe clinical reactions and it requires highly dedicated hospital facilities. Therefore, there is strong need for an accurate diagnostic test that is cheap, non-invasive and ideally can discriminate between mild and severe allergy as well. One possibility of improving diagnostics is by combining several predictors into one prediction model. Another possibility is by measuring serum IgE (sIgE) to specific allergenic peanut proteins, also called components. At the moment, 6 peanut components are commercially available and can therefore be used in clinical practice: Ara h 1, Ara h 2, Ara h 3, Ara h 6, Ara h 8, and Ara h 9. Their diagnostic accuracy can be analyzed individually or in combination with each other or other clinical predictors. In Chapter 2 we systematically reviewed current literature for studies addressing the diagnostic accuracy of the current diagnostic tests (SPT and sIgE to peanut extract) or measuring sIgE to one or more peanut components in diagnosing peanut allergy. All eligible studies were scored for risk of bias and concerns regarding applicability. Our results showed that sIgE to Ara h 2 had the best diagnostic accuracy of all diagnostic test methods that were analyzed; it was best in both diagnosing as well as excluding peanut allergy, while SPT and sIgE to peanut extract were primarily useful in excluding peanut allergy.