Peanut Allergy Diagnosis in the Context of Grass Pollen Sensitization for 125 Patients: Roles of Peanut and Cross-Reactive Carbohydrate Determinants Specific IgE

Abstract

Background: In vitro testing for food allergy may yield clinically irrelevant results due to cross-reactive carbohydrate determinants (CCD) specific immunoglobulin E (sIgE) induced by pollen exposure. The performances of 2 in vitro methods were evaluated for peanut sIgE measurement in patients allergic to grass pollen with or without subsequent allergy to peanuts. The correlation between clinically irrelevant peanut sIgE and the presence of CCD sIgE was investigated. Methods: In vitro measurement of peanut sIgE was performed using the Pharmacia ImmunoCap™ system Radio Immuno Assay (RIA) and the Immulite ® 2000 3gAllergy™ system. Discrepancies between in vitro results and peanut allergy diagnosis were evaluated by measurement of CCD sIgE using bromelain and ascorbic acid oxydase (AAO). Results: The sensitivity was 100% with both systems for the diagnosis of allergy to peanut (58 patients), nevertheless the specificity obtained with Immulite (73%) was better than that obtained using ImmunoCap (46%) in patients who were not allergic to peanuts, but who had a grass pollen allergy (n = 41). In 22 out of 41 patients who presented clinically irrelevant peanut sIgE results using ImmunoCAP, CCD sIgE was detected in 72% of the cases by bromelain and in 86% by AAO. In 11 patients out of 41 who presented irrelevant peanut sIgE results using Immulite, CCD sIgE was detected in 81% of the cases by bromelain and in 100% by AAO. Conclusion: The Immulite 2000 system had better specificity than the ImmunoCap system for accurate diagnosis of peanut allergy in patients allergic to grass pollen. CCD sIgE was identified in most of the false-positive peanut sIgE results.

Minor Interference of Cross-Reactive Carbohydrates with the Diagnosis of Respiratory Allergy in Standard Clinical Conditions

“…Most previous studies of the prevalence of CCD sensitization were performed in areas with a high prevalence of pollen allergy [8] and in selected samples of patients allergic to pollens [9,10], vegetable foods [9,10] or Hymenoptera venoms [11,12,13,14,15]. The largest of these studies included 1,831 adult and pediatric individuals with suspicion of respiratory allergy in Southern Italy [8], and reported a 23% prevalence of CCD sensitization (bromelain-sIgE >0.4 kU A /l) compared with 4.7% in our series (data not shown) from an area of predominantly mite-allergic patients.…”

“…The problem may be higher when only IgE to natural (glycosylated) allergens is used instead of SPTs. The diagnostic interference induced by CCDs may be also more relevant in populations with a higher rate of heavy alcohol consumption [6,7,22,23], a higher rate of pollen sensitization [8,9,10] or a higher rate of Hymenoptera venom allergy [11,12,13,14,15]. Hymenoptera stings, even in individuals not allergic to their venoms, are factors for CCD sensitization that may induce positivity of allergy screening tests.…”

“…In an allergy clinic in Italy, the prevalence of IgE (>0.4 kU A /l) to bromelain reached 23% [8]. Risk factors for CCD sensitization include atopy, particularly pollen sensitization [6,7,8,9,10]. The prevalence of CCD sensitization is highest among patients with a Hymenoptera venom allergy, particularly in patients with double (honeybee and wasp) IgE reactivity [11,12,13,14,15].…”

Immunoglobulin E Sensitization to Cross-Reactive Carbohydrate Determinants: Epidemiological Study of Clinical Relevance and Role of Alcohol Consumption

“…Specific IgE to these glycans, which are commonly known as cross-reactive carbohydrate determinants (CCDs), was found to be present in up to 63% of patients attending an allergy clinic due to hymenoptera venom allergy [4] and in up to 73% of subjects with allergy to 5 or more pollens [5]. In CCD-sensitized patients, in vitro IgE cross-reactivity may cause false-positive specific IgE determinations and therefore represents a diagnostic challenge [1,2,3,6]. The clinical significance of CCD-IgE is a subject of debate.…”

Food allergy: which tests are worth doing and which are not?

“…evidence of cross-reactivity is unusual 52,53 ). Again, patients may show reactivity to grasses and grains where crosssensitization of allergens does not necessarily mean clinical sensitivity to the cross-reactive allergens.…”