Long‐term prognostic value of component‐resolved diagnosis in infants and toddlers with peanut allergy

To the Editor, The interest in component-resolved diagnosis has been growing significantly in the last decade. In peanut allergy, storage proteins Ara h1 (7S-vicilin), Ara h 2 (2S-albumin), and Ara h 3 (11S-globulin) have been designated as primary sensitizers to peanut in susceptible individuals (1–3). Among available peanut molecular components, Ara h 2 is clinically the most important one (2, 3). Ara h 9 is a non-specific lipid transfer protein (nsLTP) and has been shown to be a dominant allergen, both in terms of prevalence and severity, in south European populations (2, 4). Ara h 8 (peanut PR-10 protein), Ara h 5 (profilin), and CCD are cross-reactive components associated mainly with subclinical sensitization or oral allergy syndromes (2, 5). While component-resolved diagnosis has been shown to improve specificity of peanut allergy diagnosis by differentiating between dominant and cross-reactive allergens, its long-term prognostic value has never been examined. Although in most cases peanut allergy tends to persist, previous studies have demonstrated that around 20% of children may resolve their allergy over time and resolution correlates with initial peanut IgE levels (6, 7). In the present study, we aimed to determine whether early component-resolved diagnosis at time of peanut allergy diagnosis in infants and toddlers would provide information in addition to standard specific IgE levels to better predict future evolution of the disease. We took the opportunity of a wellcharacterized cohort of peanut allergic subject from a previous study, in which 110 subjects had serum drawn at diagnosis (median age, 14 months) and stored at 80°C for future analyses (6). At the time of diagnosis, all subjects reported unequivocal clinical reaction within the past 6 months and a SPT greater than 4 mm which carries a 95% PPV in this age group (8). Subjects were followed every 2 yr for a median of 12 yr and offered DBPCFC past age 5 yr to confirm resolution if PN-IgE were below 15 kU/l (Siemens, Muenchen, Germany). Over the study period, three patients were lost to follow-up. Of the 107 remaining, 22 (21%; 95 CI = 13–34%) underwent spontaneous resolution of their peanut allergy. Initial clinical characteristics of remitters and non-remitters are shown in Table 1. Frozen sera from initial visit were then thawed and assayed simultaneously for IgE to peanut recombinant Ara h 2 and Ara h 8 (ImmunoCAP 250 and allergen components, Phadia, Saint-Quentin-en-Yvelines, France). One-hundred and four (104) sera were further analyzed for Ara h 9 and plant cross-reactive carbohydrate MUXF3 (CCD); 94 for Ara h 1; and 91 for Ara h 3 and recombinant Pru p 4 IgE levels, depending on the available quantity. As structure of plant profilins is highly conserved, peach Pru p 4 was used as a marker of profilin IgE reactivity (5). The measuring range of specific IgE to molecular components was between 0.10 and 100 kU/l. Both prevalence and levels of Ara h 8-, Ara h 9-, CCD-, and Pru p4-specific IgE were low in the cohort at diagnosis (Table 2). In contrast, specific IgE against Ara h 1, Ara h 2, and Ara h 3 was detected in 63%, 95%, and 43% of patients, respectively. This skewing in favor of dominant allergens is not surprising considering that subjects were selected based on previous clinical reactions to peanut (1, 3). Nevertheless, Ara h 2 IgE prevalence was higher in our cohort (91%) than in peanut-reactant subjects from the Swedish cohort BAMSE (73%) (2). This could be a reflection of the different age group. While BAMSE looked at children 8-yr old, children in our cohort were all younger than 18 months and thus may have been much less likely to have been sensitized to cross-reactive allergens. The sensitization profile did not vary when considering only subjects with initial PN-SPT greater or equal to 8 mm (n = 82), which carries a 95% PPV regardless of previous history of reaction (9). Ara h 9-specific IgEprevalence and levels were universally low inour population, confirming previous findingswithCentral and