The Value of Specific IgE to Peanut and Its Component Ara h 2 in the Diagnosis of Peanut Allergy

Abstract

BACKGROUND: To avoid unnecessary oral food challenges, which are time consuming, stressful, and risky, improved in vitro diagnostic methods for food allergy such as component resolved diagnostics are still under investigation.OBJECTIVE: To investigate the role of whole peanut-and peanut-component (Ara h 1, Ara h 2, Ara h 3, Ara h 6 and Ara h 8)-specific IgE levels in the diagnostic procedure of peanut allergy as well as the diagnostic properties of peanut-specific IgG and IgG(4).METHODS: Sixty-one children underwent oral peanut challenge tests for diagnostic purposes irrespective of their peanut-specific IgE levels. Peanut-specific serum IgE, IgG, and IgG(4) levels were determined by ImmunoCAP FEIA and specific IgE against individual peanut proteins by Immuno Solid-phase Allergen Chip.RESULTS: Thirty-four of 61 patients (56%) had a peanut allergy. No significant difference was observed for peanut-specific IgG or peanut-specific IgG(4) levels between patients who were allergic and tolerant patients, whereas peanut-specific IgE was significant higher in patients who were allergic than in tolerant patients (P < .005). Twenty-five of 61 children had peanut-specific IgE above a previously proposed cutoff level of 15 kU(A)/L; however, 7 of these 25 children (28%) were clinically tolerant. Ara h 2-specific IgE was significantly lower in tolerant than in patients with allergies (P < .0001). Interestingly, 94% of the patients with peanut allergies showed IgE-binding to Ara h 2. Unfortunately, 26% of the sensitized but tolerant patients have shown IgE-binding to Ara h 2 too.CONCLUSIONS: Neither the level of specific IgE to peanut nor to Ara h 2 was able to clearly distinguish patients with clinical relevant peanut allergy from those who were clinical tolerant in our population. As expected, peanut-specific IgG and IgG(4) did not improve the diagnostic procedure. (C) 2013 American Academy of Allergy, Asthma & Immunology