A Novel Immunoassay Using Recombinant Allergens Simplifies Peanut Allergy Diagnosis

Abstract

Background: Double-blind placebo-controlled food challenge (DBPCFC) is currently considered the gold standard for peanut allergy diagnosis. However, this procedure that requires the hospitalization of patients, mostly children, in specialized centers for oral exposure to allergens may cause severe reactions requiring emergency measures. Thus, a simpler and safer diagnosis procedure is needed. The aim of this study was to evaluate the diagnostic performance of a new set of in vitro blood tests for peanut allergy. Methods: The levels of IgE directed towards peanut extract and recombinant peanut allergens Ara h 1, Ara h 2, Ara h 3, Ara h 6, Ara h 7, and Ara h 8 were measured in 3 groups of patients enrolled at 2 independent centers: patients with proven peanut allergy (n = 166); pollen-sensitized subjects without peanut allergy (n = 61), and control subjects without allergic disease (n = 10). Results: Seventy-nine percent of the pollen-sensitized patients showed IgE binding to peanut, despite their tolerance to peanut. In contrast, combining the results of specific IgE to peanut extract and to recombinant Ara h 2 and Ara h 6 yielded a peanut allergy diagnosis with a 98% sensitivity and an 85% specificity at a positivity threshold of 0.10 kU/l. Use of a threshold of 0.23 kU/l for recombinant Ara h 2 increased specificity (96%) at the cost of sensitivity (93%). Conclusion: A simple blood test can be used to diagnose peanut allergy with a high level of precision. However, DBPCFC will remain useful for the few cases where immunological and clinical observations yield conflicting results.

Component-Resolved IgE Profiles in Austrian Patients with a Convincing History of Peanut Allergy

“…Our findings are in line with others showing that Ara h 2 is the most important peanut allergen [1,2,3,4,5,6,11,21,22]. Data about the prevalence and diagnostic value of Ara h 6 are rare, but in accordance with our results two studies showed that both peanut 2S albumins are recognized by IgE from the same patients in almost all cases and that the diagnostic accuracy of IgE specific to Ara h 6 in adults is as good as for Ara h 2 [1,7]. The study performed by Klemans et al [7] identified similar IgE levels for those two allergens when performing ImmunoCAP ISAC [1,7].…”

“…Our findings confirm observations from other peanut CRD studies that have demonstrated that this allergen panel enables the majority of peanut-allergic patients to be identified [1,18]. However, although the peanut extract was absolutely discriminative between patients with suspected peanut allergy and nonatopic controls, a positive sIgE result for peanut extract did not reflect the clinical relevance as it was also found in 75% of individuals without an apparent peanut allergy.…”

“…The peanut seed storage proteins Ara h 1, Ara h 2, Ara h 3 and Ara h 6 are largely recognized as the major allergens in patients who are primarily sensitized to peanut. Among them, Ara h 2 has been described as the most important peanut allergen, with a sensitization rate of 42-100% depending on the study population, whereas the sensitization rate to Ara h 1 and Ara h 3 is lower, in the range of 30-80 and 16-61%, respectively [1,2,3,4,5,6]. The diagnostic value of Ara h 6, which has only recently become available on ImmunoCAP ISAC, has been shown to be equivalent to Ara h 2 with a positive predictive value of 95% [7].…”

Which test is best for diagnosing peanut allergy in South African children with atopic dermatitis?

“…Our study concurs with previous studies that Ara h 2 seems to be the most important peanut allergen. [5][6][7][8] Ara h 2 by ImmunoCAP as well as the ISAC test were significantly more frequently positive in peanut-allergic than in asymptomatically sensitised patients. ImmunoCAP Ara h 2 was positive in 92% of peanut-allergic patients, similar to recent studies in China [14] (87% positivity) and Japan [7] (88% Ara h 2-positive).…”

“…Component testing for peanut proteins helps differentiate between nonspecific crossreactive components such as Ara h 5, 8 and 9 and specific peanut components such as Ara h 1, 2, 3 and 6, which are heat-resistant storage proteins. Ara h 2 (2S albumin storage protein) has been shown to be the most important component in prediction of food allergy in several countries, including the UK, [5] France, [6] Japan [7] and the USA, [8] with a positive result (>0.35 kU/L) to Ara h 2 having a high predictive value for peanut allergy. In Medi terranean countries, the lipid transfer factor Ara h 9 is an important peanut allergen.…”