Diagnostic accuracy of specific IgE to components in diagnosing peanut allergy: a systematic review

Prediction of pediatric peanut oral food challenge outcomes using machine learning

Background

Clinical testing, including food-specific skin and serum IgE level tests, provides limited accuracy to predict food allergy. Confirmatory oral food challenges (OFCs) are often required, but the associated risks, cost, and logistic difficulties comprise a barrier to proper diagnosis.

Objective

We sought to utilize advanced machine learning methodologies to integrate clinical variables associated with peanut allergy to create a predictive model for OFCs to improve predictive performance over that of purely statistical methods.

Methods

Machine learning was applied to the Learning Early about Peanut Allergy (LEAP) study of 463 peanut OFCs and associated clinical variables. Patient-wise cross-validation was used to create ensemble models that were evaluated on holdout test sets. These models were further evaluated by using 2 additional peanut allergy OFC cohorts: the IMPACT study cohort and a local University of Michigan cohort.

Results

In the LEAP data set, the ensemble models achieved a maximum mean area under the curve of 0.997, with a sensitivity and specificity of 0.994 and 1.00, respectively. In the combined validation data sets, the top ensemble model achieved a maximum area under the curve of 0.871, with a sensitivity and specificity of 0.763 and 0.980, respectively.

Conclusions

Machine learning models for predicting peanut OFC results have the potential to accurately predict OFC outcomes, potentially minimizing the need for OFCs while increasing confidence in food allergy diagnoses.

Indirect Basophil Activation Test for Peanut Allergy Diagnosis Using Human Donor Basophils

The basophil activation test (BAT) is a promising test for the replacement of the expensive, time-consuming, and patient-unfriendly oral food challenge (OFC). However, the BAT requires a fresh blood sample which has to be analyzed within 1 day, which can be a logistical constraint. The indirect or passive basophil activation test (iBAT) with human donor basophils and patient serum that can be stored for a long time (1) enables laboratories to perform the assay at any time, (2) gives the possibility to analyze different allergens in the course of time without the need of a new blood sample, and (3) does not suffer from inconclusive results due to nonresponder basophils. The advantage of this iBAT with human donor basophils over the use of basophil or mast cell lines is that this iBAT can be executed without the need of laboratory facilities for cell culture.

A comparison of healthcare utilization and outcomes following skin vs. serum-specific IgE allergy testing

OBJECTIVE

To compare the cost, healthcare utilization, and outcomes between skin and serum-specific IgE (sIgE) allergy testing.

METHODS

This retrospective cohort study used IBM® MarketScan claims data, from which commercially insured individuals who initiated allergy testing between January 1 and December 31, 2018 with at least 12 months of enrollment data before and after index testing date were included. Cost of allergy testing per patient was estimated by testing pattern: skin only, sIgE only, or both. Multivariable linear regression was used to compare healthcare utilization and outcomes, including office visits, allergy and asthma-related prescriptions, and emergency department (ED) and urgent care (UC) visits between skin and sIgE testing at 1-year post testing (α = 0.05).

RESULTS

The cohort included 168,862 patients, with a mean (SD) age of 30.8 (19.5) years; 100,666 (59.7%) were female. Over half of patients (56.4%, n = 95,179) had skin only testing, followed by 57,291 patients with sIgE only testing and 16,212 patients with both testing. The average cost of allergy testing per person in the first year was $430 (95% CI $426-433) in patients with skin only testing, $187 (95% CI $183-190) in patients with sIgE only testing, and $532 (95% CI $522-542) in patients with both testing. At 1-year follow-up post testing, there were slight increases in allergy and asthma-related prescriptions, and notable decreases in ED visits by 17.0-17.4% and in UC visits by 10.9-12.6% for all groups (all p < 0.01). Patients with sIgE-only testing had 3.2 fewer allergist/immunologist visits than patients with skin-only testing at 1-year follow-up (p < 0.001). Their healthcare utilization and outcomes were otherwise comparable.

CONCLUSIONS

Allergy testing, regardless of the testing method used, is associated with decreases in ED and UC visits at 1-year follow-up. sIgE allergy testing is associated with lower testing cost and fewer allergist/immunologist visits, compared to skin testing.

Peanut Allergy and Component-Resolved Diagnostics Possibilities-What Are the Benefits?

Peanut allergy is a widespread and potentially life-threatening condition that affects both children and adults, with a growing incidence worldwide. It is estimated to affect around 1-2% of the population in several developed countries. Component-resolved diagnostics is a modern approach to allergy diagnosis that focuses on identifying specific allergenic proteins to provide precise diagnoses and personalized treatment plans. It is a technique that enables the analysis of specific IgE antibodies against tightly defined molecules (components) that constitute the allergen. Component-resolved diagnostics is particularly valuable in peanut allergy diagnosis, helping to determine allergen components associated with severe reactions. It also aids in predicting the course of the allergy and enables the development of personalized immunotherapy plans; however, the full application of it for these purposes still requires more precise studies. In this paper, we present the current knowledge about peanut allergy and component-resolved diagnostics possibilities. We discuss the possibilities of using molecular diagnostics in the diagnosis of peanut allergy. We focus on examining and predicting the development of peanut allergy, including the risk of anaphylaxis, and describe the latest data related to desensitization to peanuts.

Developing a Prediction Model for Determination of Peanut Allergy Status in the Learning Early About Peanut Allergy (LEAP) Studies

BACKGROUND

The Learning Early About Peanut Allergy (LEAP) study team developed a protocol-specific algorithm using dietary history, peanut-specific IgE, and skin prick test (SPT) to determine peanut allergy status if the oral food challenge (OFC) could not be administered or did not provide a determinant result.

OBJECTIVE

To investigate how well the algorithm determined allergy status in LEAP; to develop a new prediction model to determine peanut allergy status when OFC results are not available in LEAP Trio, a follow-up study of LEAP participants and their families; and to compare the new prediction model with the algorithm.

METHODS

The algorithm was developed for the LEAP protocol before the analysis of the primary outcome. Subsequently, a prediction model was developed using logistic regression.

RESULTS

Using the protocol-specified algorithm, 73% (453/617) of allergy determinations matched the OFC, 0.6% (4/617) were mismatched, and 26% (160/617) participants were nonevaluable. The prediction model included SPT, peanut-specific IgE, Ara h 1, Ara h 2, and Ara h 3. The model inaccurately predicted 1 of 266 participants as allergic who were not allergic by OFC and 8 of 57 participants as not allergic who were allergic by OFC. The overall error rate was 9 of 323 (2.8%) with an area under the curve of 0.99. The prediction model additionally performed well in an external validation cohort.

CONCLUSION

The prediction model performed with high sensitivity and accuracy, eliminated the problem of nonevaluable outcomes, and can be used to estimate peanut allergy status in the LEAP Trio study when OFC is not available.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Changes in Serum Protein-Peptide Patterns in Atopic Children Allergic to Plant Storage Proteins

Next to cow's milk and eggs, plant foods, i.e., legumes, tree nuts and cereal grains, most often sensitise atopic children. Storage proteins constitutes the most relevant protein fraction of plant foods, causing primary sensitisation. They exhibit strong allergenic properties and immunogenicity. Our goal was to analyse sensitisation to 26 plant storage proteins in a group of 76 children aged 0-5 years with chronic symptoms of atopic dermatitis using Allergy Explorer ALEX2 and to discover changes in serum protein-peptide patterns in allergic patients with the use of MALDI-TOF-MS. We reported that 25% of children were allergic to 2S albumins, 19.7% to 7S globulins, 13.2% to 11S globulins and 1.3% to cereal prolamins. The most common allergenic molecules were Ara h 1 (18.4%), Ara h 2 (17.1%), Ara h 6 (15.8%) and Ara h 3 (11.8%) from peanuts, and the mean serum sIgE concentrations in allergic patients were 10.93 kUA/L, 15.353 kUA/L, 15.359 kUA/L and 9.038 kUA/L, respectively. In children allergic to storage proteins compared to the other patients (both allergic and non-allergic), the cell cycle control protein 50A, testis-expressed sequence 13B, DENN domain-containing protein 5A and SKI family transcriptional corepressor 2 were altered. Our results indicate that the IgE-mediated allergy to storage proteins is a huge problem in a group of young, atopic children, and show the potential of proteomic analysis in the prediction of primary sensitisation to plant foods. It is the next crucial step for understanding the molecular consequences of allergy to storage proteins.

Predicting probability of tolerating discrete amounts of peanut protein in allergic children using epitope-specific IgE antibody profiling

BACKGROUND

IgE-epitope profiling can accurately diagnose clinical peanut allergy.

OBJECTIVE

We sought to determine whether sequential (linear) epitope-specific IgE (ses-IgE) profiling can provide probabilities of tolerating discrete doses of peanut protein in allergic subjects undergoing double-blind, placebo-controlled food challenges utilizing PRACTALL dosing.

METHODS

Sixty four ses-IgE antibodies were quantified in blood samples using a bead-based epitope assay. A pair of ses-IgEs that predicts Cumulative Tolerated Dose (CTD) was determined using regression in 75 subjects from the discovery cohort. This epitope-based predictor was validated on 331 subjects from five independent cohorts (ages 4-25 years). Subjects were grouped based on their predicted values and probabilities of reactions at each CTD threshold were calculated.

RESULTS

In discovery, an algorithm using two ses-IgE antibodies was correlated with CTDs (rho = 0.61, p < .05); this correlation was 0.51 (p < .05) in validation. Using the ses-IgE-based predictor, subjects were assigned into "high," "moderate," or "low" dose-reactivity groups. On average, subjects in the "high" group were four times more likely to tolerate a specific dose, compared with the "low" group. For example, predicted probabilities of tolerating 4, 14, 44, and 144 or 444 mg in the "low" group were 92%, 77%, 53%, 29%, and 10% compared with 98%, 95%, 94%, 88%, and 73% in the "high" group.

CONCLUSIONS

Accurate predictions of food challenge thresholds are complex due to factors including limited responder sample sizes at each dose and variations in study-specific challenge protocols. Despite these limitations, an epitope-based predictor was able to accurately identify CTDs and may provide a useful surrogate for peanut challenges.

BSACI guideline for the diagnosis and management of pollen food syndrome in the UK

Pollen food syndrome (PFS) is a highly prevalent food allergy affecting pollen-sensitized children and adults. Sufferers experience allergic symptoms when consuming raw plant foods, due to the homology between the pollen allergens and unstable proteins in these foods. The triggers involved can vary depending on the pollen sensitization, which in turn is affected by geographical location. The British Society of Allergy and Clinical Immunology (BSACI) Standards of Care Committee (SOCC) identified a need to develop a guideline for the diagnosis and management of PFS in the United Kingdom (UK). Guidelines produced by the BSACI use either the GRADE or SIGN methodology; due to a lack of high-quality evidence these recommendations were formulated using the SIGN guidelines, which is acknowledged to be less robust than the GRADE approach. The correct diagnosis of PFS ensures the avoidance of a misdiagnosis of a primary peanut or tree nut allergy or confusion with another plant food allergy to non-specific lipid transfer proteins. The characteristic foods involved, and rapid-onset oropharyngeal symptoms, mean PFS can often be diagnosed from the clinical history alone. However, reactions involving tree nuts, peanuts and soya milk or severe/atypical reactions to fruits and vegetables may require additional diagnostic tests. Management is through the exclusion of known trigger foods, which may appear to be simple, but is highly problematic if coupled with a pre-existing food allergy or for individuals following a vegetarian/vegan diet. Immunotherapy to pollens is not an effective treatment for PFS, and although oral or sublingual immunotherapy to foods seems more promising, large, controlled studies are needed. The typically mild symptoms of PFS can lead to an erroneous perception that this condition is always easily managed, but severe reactions can occur, and anxiety about the onset of symptoms to new foods can have a profound effect on quality of life.

Current insights: a systemic review of therapeutic options for peanut allergy

PURPOSE OF REVIEW

With increasing prevalence of peanut allergy (PA) globally and the greater risk of potential reactions occurring due to the leading role of nuts in food products, PA has become a significant public health concern over the past decade, affecting up to 5 million of the US adult population. This review details updates and advances in prevalence, diagnosis, and immunotherapies that have occurred over the past year.

RECENT FINDINGS

Therapeutic and diagnostic advances remain at the forefront of research and have continued to push the food allergy (FA) field forward to provide a promising role in the detection and treatment of PA. The FA field has researched significant advances in peanut immunotherapy, biomarker diagnosis, and quality of life (QoL) improvement.

SUMMARY

Given the burden and consequences for individuals with PA, these advances delivered in clinical practice can significantly improve the QoL of individuals with PA and their caregivers. Ongoing studies will continue to investigate long-term outcome measures of desensitisation and effective management plans tailored to the families' needs.

The Indirect Basophil Activation Test Is a Safe, Reliable, and Accessible Tool to Diagnose a Peanut Allergy in Children

BACKGROUND

The gold standard for the diagnosis of a peanut allergy is an oral food challenge (OFC), but it is a time-consuming, patient-unfriendly, and expensive test. The in vitro direct basophil activation test (BAT) for peanuts was shown to be a promising diagnostic tool for replacing the OFC.

OBJECTIVE

To determine the diagnostic accuracy of the indirect (passive) BAT. Compared with the direct BAT, the timing of the indirect BAT is more flexible, and the problem of nonresponding basophils (unresponsive to IgE receptor-mediated signaling) is circumvented.

METHODS

In 74 children, suspected of peanut allergy and eligible for an OFC, indirect BAT results for peanut extract, Ara h2, and Ara h6 were compared with the results of a double-blind placebo-controlled food challenge. The reactivity and sensitivity of the basophils in the BAT were correlated to both the allergy status and the threshold dose in the OFC.

RESULTS

The combined basophil reactivity for Ara h2 and Ara h6 showed the highest accuracy (94%) for the diagnosis of a peanut allergy, with positive and negative predictive values of 96% and 89%, respectively. The sensitivity of the basophils for Ara h2 significantly discriminates between patients who tolerated up to 0.4 g of peanut protein in the OFC and those who did not.

CONCLUSIONS

Because the indirect BAT showed a high diagnostic accuracy for peanut allergy, it is a promising alternative to the classical direct BAT and could lead to a reduction in OFC use.

Real world use of peanut component testing among children in the Chicago metropolitan area

Background: Peanut component tests (PCT) have become important in the evaluation of peanut allergy. There remains a paucity of research across the United States in investigating the utility of PCT in clinical practice in conjunction with current standards of care. Objective: The primary aims were to evaluate the performance and sensitization patterns of PCT in clinical practice when first available at our institution. Methods: We performed a retrospective chart review of 184 children with PCT and oral food challenge (OFC) results between 2012 and 2017. Simple logistic regression models assessed the associations between PCT and OFC outcomes. Receiver operator characteristic curves were constructed, and a predicted probability curve was derived for Ara h2. Results: The median (interquartile range [IQR]) age at OFC was 4 years (2-7 years), and 111 patients (60%) were boys. Ara h 2 was the most commonly sensitized PCT. Sixty-one patients (33%) reacted at OFC. Ara h 2 specific immunoglobulin E (sIgE) ≥ 0.35 kU_A/L was associated with increased odds of reacting at OFC (odds ratio 5.91 95% confidence interval, 2.93-11.89; p < 0.001); however, 19 patients (37%) positive for Ara h 2 did not react. Ara h 2 sIgE of 0.49 kU_A/L and 4.58 kU_A/L were associated with 50% and 90% probability, respectively, of reacting at OFC. Among those sensitized only to Ara h 8 or 9 (n = 21), 86% had no reaction. There was no statistically significant association with polysensitization to Ara h 1, 2, and 3, and peanut OFC outcome. Conclusion: Although the Ara h 2 sIgE value was associated with clinical reactivity, a significant proportion of the patients sensitized to Ara h 2 tolerated peanut. OFC remains an important tool in the evaluation of peanut allergy.

Protocol for a systematic review of the diagnostic test accuracy of tests for IgE-mediated food allergy

BACKGROUND

The European Academy of Allergy and Clinical Immunology (EAACI) is in the process of updating the guidelines on the diagnosis and management of food allergy. The existing guidelines are based on a systematic review of the literature until 30 September 2012. Therefore, a new systematic review must be undertaken to inform the new guidelines. This systematic review aims to assess the accuracy of index tests to support the diagnosis of IgE-mediated food allergy.

METHODS

The databases Cochrane CENTRAL (Trials), MEDLINE (OVID) and Embase (OVID) will be searched for diagnostic test accuracy studies from 1 October 2012 to 30 June 2021. Inclusion and exclusion criteria will be used to select appropriate studies. Data from these studies will be extracted and tabulated, and then reviewed for risk of bias and applicability using the QUADAS-2 tool. All evaluations will be done in duplicate. Studies with a high risk of bias and low applicability will be excluded. Meta-analysis will be performed if there are three or more studies of the same index test and food.

RESULTS

A protocol for the systematic review and meta-analyses is presented and was registered using Prospero prior to commencing the literature search.

DISCUSSION

Oral food challenges are the reference standard for diagnosis but involve considerable risks and resources. This protocol for systematic review aims to assess the accuracy of various tests to diagnose food allergy, which can be useful in both clinical and research settings.

Bringing the Next Generation of Food Allergy Diagnostics into the Clinic

Food allergy diagnosis has a massive impact on the lives of patients and their families. Despite recent developments with specific IgE to component allergens, a significant proportion of patients assessed for possible food allergy require oral food challenge to ensure an accurate diagnosis. More precise diagnostic methods are required to reduce the need for oral food challenges. Bead-based epitope assays and cellular tests, such as basophil activation and mast cell tests are the most novel and promising tests on the horizon. There is a pathway to pursue to enable their incorporation in clinical practice, including standardization, technical validation, clinical validation, external validation, overcoming practical and logistical issues, and regulatory approval. Valuable clinical application of these tests goes beyond diagnosis and includes risk assessment to identify allergic patients who are most sensitive and at risk for severe allergic reactions, and to define prognosis and assess clinical response to immunomodulatory treatments.

Peanut components measured by ISAC: comparison with ImmunoCap and clinical relevance in peanut allergic children

Background

Specific IgE (sIgE) against the peanut component Arachis hypogaea (Ara h) 2 has been shown to be the most important allergen to discriminate between peanut allergy and peanut tolerance. Several studies determined sIgE cut off values for Ara h 2, determined by singleplex measurements. However, cut off values for Ara h 2 from multiplex arrays are less well defined. The aim of this study was to evaluate the correlation between Ara h 2 sIgE determined by singleplex versus multiplex measurements and to assess the diagnostic value of the different peanut components included in Immuno Solid-phase Allergen Chip (ISAC) multiplex analysis in children with a suspected peanut allergy.

Methods

In this retrospective study we analyzed Ara h 2 sIgE values with singleplex Fluorescence Enzyme Immunoassay (FEIA, ImmunoCap) and multiplex microarray (ISAC) measurements in 117 children with a suspected peanut allergy. Also, other peanut components measured by ISAC were analyzed. Double blinded placebo controlled oral food challenges were used as golden standard.

Results

Among all studied peanut components FEIA Ara h 2 sIgE showed the highest area under the curve (AUC, 0.922), followed by ISAC Ara h 6 and Ara h 2 sIgE with AUCs of respectively 0.906 and 0.902. Best cut off values to diagnose peanut allergy were 4.40 kU/l for FEIA Ara h 2 sIgE and, 7.43 ISU and 8.13 ISU for respectively Ara h 2 and Ara h 6 sIgE in ISAC microarray. Ara h 2 sIgE determined in FEIA and ISAC showed a good correlation (r = 0.88; p < 0.01).

Conclusion

Ara h 6 and Ara h 2 sIgE in multiplex ISAC are both good predictors of clinical peanut allergy in Dutch children, and their performance is comparable to the use of Ara h 2 in singleplex FEIA. The simultaneous measurement of different peanut components using ISAC is an advantage and clinically useful to detect peanut allergic children that are Ara h 2 negative but sensitized to other peanut proteins such as Ara h 6.

Basophil activation test shows high accuracy in the diagnosis of peanut and tree nut allergy: The Markers of Nut Allergy Study

BACKGROUND

Peanut and tree nut allergies are the most important causes of anaphylaxis. Co-reactivity to more than one nut is frequent, and co-sensitization in the absence of clinical data is often obtained. Confirmatory oral food challenges (OFCs) are inconsistently performed.

OBJECTIVE

To investigate the utility of the basophil activation test (BAT) in diagnosing peanut and tree nut allergies.

METHODS

The Markers Of Nut Allergy Study (MONAS) prospectively enrolled patients aged 0.5-17 years with confirmed peanut and/or tree nut (almond, cashew, hazelnut, pistachio, walnut) allergy or sensitization from Canadian (n = 150) and Austrian (n = 50) tertiary pediatric centers. BAT using %CD63⁺ basophils (SSClow/CCR3pos) as outcome was performed with whole blood samples stimulated with allergen extracts of each nut (0.001-1000 ng/mL protein). BAT results were assessed against confirmed allergic status in a blinded fashion to develop a generalizable statistical model for comparison to extract and marker allergen-specific IgE.

RESULTS

A mixed effect model integrating BAT results for 10 and 100 ng/mL of peanut and individual tree nut extracts was optimal. The area under the ROC curve (AUROC) was 0.98 for peanut, 0.97 for cashew, 0.92 for hazelnut, 0.95 for pistachio, and 0.97 for walnut. The BAT outperformed sIgE testing for peanut or hazelnut and was comparable for walnut (AUROC 0.95, 0.94, 0.92) in a sub-analysis in sensitized patients undergoing OFC.

CONCLUSIONS

Basophil activation test can predict allergic clinical status to peanut and tree nuts in multi-nut-sensitized children and may reduce the need for high-risk OFCs in patients.

New Insights in Therapy for Food Allergy

Food allergy is an increasing problem worldwide, with strict avoidance being classically the only available reliable treatment. The main objective of this review is to cover the latest information about the tools available for the diagnosis and treatment of food allergies. In recent years, many efforts have been made to better understand the humoral and cellular mechanisms involved in food allergy and to improve the strategies for diagnosis and treatment. This review illustrates IgE-mediated food hypersensitivity and provides a current description of the diagnostic strategies and advances in different treatments. Specific immunotherapy, including different routes of administration and new therapeutic approaches, such as hypoallergens and nanoparticles, are discussed in detail. Other treatments, such as biologics and microbiota, are also described. Therefore, we conclude that although important efforts have been made in improving therapies for food allergies, including innovative approaches mainly focusing on efficacy and safety, there is an urgent need to develop a set of basic and clinical results to help in the diagnosis and treatment of food allergies.

Update on food allergy

Food allergy is a major public health issue with growing prevalence in the urbanized world and significant impact on the lives of allergic patients and their families. Research into the risk factors that have contributed to this increase and their underlying immune mechanisms could lead us to definitive ways for treatment and prevention of food allergy. For the time being, introduction of peanut and other allergenic foods in the diet at the time of weaning seems to be an effective way to prevent the development of food allergy. Improved diagnosis and appropriate management and support of food allergic patients are central to patient care with food immunotherapy and biologics making the transition to clinical practice. With the new available treatments, it is becoming increasingly important to include patients' and family preferences to provide a management plan tailored to their needs.

Peanut diversity and specific activity are the dominant IgE characteristics for effector cell activation in children

Background

IgE mediates allergic reactions to peanut; however, peanut-specific IgE (sIgE) levels do not always equate to clinical peanut allergy. Qualitative differences between sIgE of peanut-sensitized but tolerant (PS) and peanut-allergic (PA) individuals may be important.

Objective

We sought to assess the influence of IgE characteristics on effector cell activation in peanut allergy.

Methods

A cohort of 100 children was studied. The levels of IgE to peanut and peanut components were measured. Specific activity (SA) was estimated as the ratio of allergen-sIgE to total IgE. Avidity was measured by ImmunoCAP with sodium thiocyanate. IgE diversity was calculated on the basis of ImmunoCAP-Immuno Solid-phase Allergen Chip assays for 112 allergens or for 6 peanut allergens. Whole-blood basophils and mast cell line Laboratory of Allergic Diseases 2 sensitized with patients’ plasma were stimulated with peanut or controls and assessed by flow cytometry.

Results

SA to peanut (P < .001), Ara h 1 (P = .004), Ara h 2 (P < .001), Ara h 3 (P = .02), and Ara h 6 (P < .001) and the avidity of peanut-sIgE (P < .001) were higher in PA than in PS individuals. Diversity for peanut allergens was greater in PA individuals (P < .001). All IgE characteristics were correlated with basophil and mast cell activation. Peanut SA (R = 0.447) and peanut diversity (R = 0.440) had the highest standardized β-coefficients in combined multivariable regression models (0.447 and 0.440, respectively).

Conclusions

IgE specificity, SA, avidity, and peanut diversity were greater in PA than in PS individuals. IgE peanut SA and peanut diversity had the greatest influence on effector cell activation and could be used clinically.

Recent advances in the management of nut allergy

Peanut/tree nut allergy is common and has been associated with particularly severe reactions. Epidemiological data have shown that the prevalence ranges between 0.05% and 4.9% for tree nut and between 0.5% and 3% for peanut. These large variations can be explained by differences in the age of included patients and the geographical region. In addition, the food consumption modality (ie, raw versus roasted) plays a major role, as heat treatment has the capacity to modify the allergenicity of nuts and legumes. Nut allergies tend to persist into adulthood and consequently have a high impact on quality of life.

Recently, it has been demonstrated that a significant proportion of nut allergic patients are able to tolerate other nuts. As opposed to the avoidance of all nuts, this approach is currently proposed in several tertiary allergy centers. However, diagnosis of nut allergy is particularly difficult due to co-sensitization leading to high rate of false positive skin prick tests and/or specific IgE to whole allergen extracts. The use of component resolved diagnosis leads to major improvement of diagnosis, particularly to distinguish between primary and secondary nut allergies. The basophil activation test has been suggested to be useful but is still used mainly as a research tool. Thus, diagnosis remains mainly based on the oral food challenge, which is considered as the gold standard.

Regarding treatment, avoidance remains the cornerstone of management of nut allergy. Oral immunotherapy is increasingly proposed as an alternative management strategy.

Peanut allergy diagnosis: A 2020 practice parameter update, systematic review, and GRADE analysis

Given the burden of disease and the consequences of a diagnosis of peanut allergy, it is important that peanut allergy be accurately diagnosed so that an appropriate treatment plan can be developed. However, a test that indicates there is peanut sensitization present (eg, a "positive" test) is not always associated with clinical reactivity. This practice parameter addresses the diagnosis of IgE-mediated peanut allergy, both in children and adults, as pertaining to 3 fundamental questions, and based on the systematic reviews and meta-analyses, makes recommendations for the clinician who is evaluating a patient for peanut allergy. These questions relate to when diagnostic tests should be completed, which diagnostic tests to utilize, and the utility (or lack thereof) of diagnostic testing to predict the severity of a future allergic reaction to peanut.

Mapping and IgE-binding capacity analysis of heat/digested stable epitopes of mud crab allergens

Mud crab (Scylla paramamosain) is widely consumed after thermal processing. It is necessary to comprehensively evaluate of the allergenic potential and epitopes of allergens in high temperature-pressure (HTP) treated S. paramamosain. Tropomyosin and arginine kinase presented higher prevalence (30.77% and 42.13%) than the other three important crab allergens by component-resolved diagnosis. The surface expression of basophils CD63 and CD203c were decreased in HTP treated crab, an effect that was even more evident after digestion and absorption by the intestinal Caco-2 cell model. Of the 35 stable epitope, six were for the first time identified in shellfish. Seven heat/digested stable peptides of tropomyosin retained IgE-binding capacity and were shown to interact with MHC-II. Five epitopes (amino acids 19-29, 99-109, 153-162, 170-188 and 211-221) were the first identified in crab. The study provides insight into prevention and therapy of crab allergy, as well as helps to reduce crab allergenicity during thermal processing.

Early epitope-specific IgE antibodies are predictive of childhood peanut allergy

BACKGROUND

Peanut allergy is characterized by the development of IgE against peanut antigen.

OBJECTIVE

We sought to evaluate the evolution of epitope-specific (es)IgE and esIgG4 in a prospective cohort of high-risk infants to determine whether antibody profiles can predict peanut allergy after age 4 years.

METHODS

The end point was allergy status at age 4+ years; samples from 293 children were collected at age 3 to 15 months and 2 to 3 and 4+ years. Levels of specific (s)IgE and sIgG4 to peanut and component proteins, and 50 esIgE and esIgG4 were quantified. Changes were analyzed with mixed-effects models. Machine learning algorithms were developed to identify a combination of antigen- and epitope-specific antibodies that using 3- to 15-month or 2- to 3-year samples can predict allergy status at age 4+ years.

RESULTS

At age 4+ years, 38% of children were Tolerant or 14% had Possible, 8% Convincing, 24% Serologic, and 16% Confirmed allergy. At age 3 to 15 months, esIgE profiles were similar among groups, whereas marked increases were evident at age 2 and 4+ years only in Confirmed and Serologic groups. In contrast, peanut sIgE level was significantly lower in the Tolerant group at age 3 to 15 months, increased in Confirmed and Serologic groups but decreased in Convincing and Possibly Allergic groups over time. An algorithm combining esIgEs with peanut sIgE outperformed different clinically relevant IgE cutoffs, predicting allergy status on an "unseen" set of patients with area under the curves of 0.84 at age 3 to 15 months and 0.87 at age 2 to 3 years.

CONCLUSIONS

Early epitope-specific plus peanut-specific IgE is predictive of allergy status at age 4+ years.

Added Diagnostic Value of Peanut Component Testing: A Cross-Sectional Study in Australian Children

BACKGROUND

Peanut components are widely used in clinical practice; however, their utility to predict challenge outcome in the Australian children, outside of infants, is not well studied.

OBJECTIVE

Can peanut component testing predict outcome of challenge in peanut-allergic children.

METHODS

All children attending peanut challenges, regardless of previous allergic reactions to peanut or sensitization (skin prick test or peanut IgE) alone, were recruited. Serum collected before the challenge was analyzed for peanut IgE and Ara h 1, 2, 3, 6, 8, and 9 (ImmunoCap).

RESULTS

Of the 222 children recruited, 89 (40%) were allergic on oral food challenge. Ara h 2 and 6 performed similarly to peanut IgE and skin prick test in predicting challenge outcome (area under the curve, 0.84-0.87). No baseline clinical characteristics, including past history, predicted challenge outcome. By logistic regression, degree of polysensitization to Ara h 1, 2, or 3 increased the odds of allergic reaction at oral food challenge at 0.35 and 1.0 kU_A/L cutoff levels (P < .001 for both). All 11 children sensitized (>0.35 kU_A/L) to Ara h 1, 2, and 3 reacted to peanut challenge. Degree of polysensitization at more than 1.0 kU_A/L was associated with a lower cumulative eliciting dose (P = .016) and with severity of allergic reaction on challenge (P = .007).

CONCLUSIONS

In our cohort, sensitization to the combination of Ara h 1, 2, and 3 was highly predictive of peanut allergy. Overall, only Ara h 2 as individual component most correlated with severity of reaction at challenge and adrenaline use. Ara h 8 and 9 were not useful in predicting challenge outcome.

Immunoglobulin E-Binding Pattern of Canadian Peanut Allergic Children and Cross-Reactivity with Almond, Hazelnut and Pistachio

Peanut allergic individuals can be both co-sensitized and co-allergic to peanut and tree nuts. At the moment, standard diagnostic approaches do not always allow differentiation between clinically relevant sensitization and nonsignificant cross-reactions, and the responsibility of each allergen remains unclear. The objective of this study was therefore to determine a peanut sensitization profile in a cohort of Canadian peanut allergic children and assess the immunoglobulin E (IgE) molecular cross-reactivity between peanut, almond, hazelnut and pistachio. The specific IgE (sIgE) levels of each patient serum were determined by ImmunoCAP, indirect ELISA and immunoblot to examine their sIgE-binding levels and profiles to peanut proteins. Reciprocal inhibition ELISA and immunoblotting were used to study sIgE cross-reactions between peanut and the selected tree nuts using an adjusted and representative serum pool of the nine allergic patients. The results showed that the prepared peanut and tree nut protein extracts allowed for the detection of the majority of peanut and selected tree nut known allergens. The reciprocal inhibition ELISA experiments showed limited sIgE cross-reactivities between peanut and the studied tree nuts, with peanut being most likely the sensitizing allergen and tree nuts the cross-reactive ones. In the case of hazelnut and pistachio, a coexisting primary sensitization to hazelnut and pistachio was also demonstrated in the serum pool. Reciprocal inhibition immunoblotting further revealed that storage proteins (2S albumin, 7S vicilin and 11S legumin) could possibly account for the observed IgE-cross-reactions between peanut and the studied tree nuts in this cohort of allergic individuals. It also demonstrated the importance of conformational epitopes in the exhibited cross-reactions.

Change in exhaled nitric oxide during peanut challenge is related to severity of reaction

BACKGROUND

Peanut allergy affects 3% of Australian children and has a higher risk of anaphylaxis than most food allergies. Predicting who is likely to develop anaphylaxis is still an inexact science. The fraction of exhaled nitric oxide (FeNO) shows promise as a biomarker involved in peanut allergy, as nitric oxide plays a role in inhibiting mast cell degranulation which is relevant in anaphylaxis, where mast cell degranulation plays a mediator role. The aim of this study was to assess the change in FeNO in children during peanut challenge.

METHODS

Thirty-six children aged from 5 to 17 years were recruited for open-labelled peanut challenge. Participants had skin prick test to peanut performed, and serum collected for Ara h2 specific IgE and peanut specific IgE. FeNO was measured by portable device (NIOX VERO) prior to and throughout the peanut challenge.

RESULTS

When grouped according to reaction type at peanut challenge (anaphylaxis, clinical allergy not anaphylaxis and tolerant), there were significant differences in the mean change in FeNO measurement between the anaphylaxis group and the clinical allergy, not anaphylaxis group (p = 0.005), and between the anaphylaxis group and tolerant group (p < 0.0001).

CONCLUSIONS

FeNO decreased more significantly in those who subsequently developed anaphylaxis than in those with clinical allergy, not anaphylaxis or negative peanut challenge (tolerance). As a bedside test that can be used in children, it has potential for further research into mechanisms of anaphylaxis in food allergy and potentially assists in predicting an imminent anaphylactic reaction in some patients.Trial registration ClinicalTrials.gov: PEAnut Anaphylaxis Predictors (PEAAP) NCT02424136.

Current perspectives on peanut allergy

Peanut allergy is increasingly prevalent and for most patients is a life-long condition, with the potential to cause life-threatening reactions. Accurate diagnosis and appropriate management are essential to minimise risks due to accidental peanut exposure. Current management strategies focus on strict allergen avoidance and access to emergency medicines to treat potential reactions; however, active approaches are an area of intense research. Promising new methods of food allergen immunotherapy are set to change the approach to managing peanut allergic patients in the near future.

Diagnosis of peanut allergy using continuous likelihood ratios

BACKGROUND

Peanut allergy (PA) is associated with an economic and psychological burden on patients and families. Its diagnosis includes tests for peanut specific immunoglobulin E (sIgE), the values of which usually are categorized as positive or negative using a predefined cutoff (usually 0.35 kU/L). With the use of Bayes' theorem, this categorization can be replaced with a continuous interpretation of sIgE, which accounts for the prevalence of PA and history of ingestion.

OBJECTIVE

To evaluate a method for estimating the likelihood ratio (LR) for each value of sIgE by performing a pilot investigation with the results of oral food challenges. The LR could be used to estimate the probability of PA.

METHODS

The outcomes of oral food challenges and serum IgE values from 117 children seen in an allergy clinic between January 2017 and November 2019 were obtained. Polynomial regression of the receiver operation characteristics curve was used to determine an LR for each value of sIgE. Linear regression was used to estimate an LR for each value of sIgE.

RESULTS

sIgE ranged from less than 0.1 kU/L to 35 kU/L. Bayes' theorem and a receiver operation characteristics curve were used to estimate LRs for each value of peanut sIgE. The value of IgE associated with an LR of 1 was 0.22 kU/L, which is comparable to other studies that used a value of 0.35 kU/L to separate positive from negative results.

CONCLUSION

When combined with estimates of pretest probability, this method should permit the development of computerized decision-making algorithms to estimate the probability that a patient has PA.

Peanut allergy diagnosis: Moving from basic to more elegant testing

Peanut allergy (PNA) is an IgE-mediated immune disorder, which merits particular attention due to its impact on the health and quality of life of millions of patients worldwide. PNA tends to develop in early life and resolves in only 20% of peanut-allergic children. It accounts for the majority of severe food-related allergic reactions. An accurate diagnosis of PNA is vital. In this review, we present the approach to the diagnosis of peanut allergy, starting from the history and proceeding to measures of overall sensitization and then to component-resolved diagnostics and oral food challenges as indicated. Additional testing in development includes basophil activation testing and determination of epitopes for peanut-allergic responses. Based on the literature, stepwise approaches and predictive models for diagnosing PNA are also presented.

Peanut Allergy: New Advances and Ongoing Controversies

Peanut allergy is one of the most common food allergies in children, with increasing prevalence over time. The dual-allergen exposure hypothesis now supports transcutaneous sensitization to peanut as a likely pathophysiologic mechanism for peanut allergy development. As a result, there is emerging evidence that early peanut introduction has a role in peanut allergy prevention. Current first-line diagnostic tests for peanut allergy have limited specificity, which may be enhanced with emerging tools such as component-resolved diagnostics. Although management of peanut allergy includes avoidance and carrying an epinephrine autoinjector, risk of fatal anaphylaxis is extremely low, and there is minimal risk related to cutaneous or inhalational exposure. Quality of life in children with peanut allergy requires significant focus. Moving forward, oral and epicutaneous immunotherapy are emerging and exciting tools that may have a role to play in desensitization to peanut.

Accuracy of component-resolved diagnostics in peanut allergy: Systematic literature review and meta-analysis

BACKGROUND

Peanut allergy diagnosis relies on clinical reactivity to peanut supported by detection of specific IgE (sIgE) antibodies. Extract-based sIgE tests have low specificity, so component-resolved diagnostics may complement whole-extract testing.

METHODS

We systematically collected peanut allergen component data in seven databases and studied the diagnostic accuracy of peanut storage proteins (Arah1, 2, 3) and cross-reactive peanut proteins (Arah8 PR-10 and Arah9 lipid transfer protein) through meta-analyses. The systematic literature review included studies employing peanut components and oral food challenge (OFC) as reference standard in patients suspected of peanut allergy. Data for component sIgE at pre-defined detection thresholds were extracted and combined in random-effects bivariate meta-analyses. Risk of bias was assessed as recommended by Cochrane, with two additional quality items of importance for this review.

RESULTS

Nineteen eligible studies presented data suitable for meta-analysis. In cross-sectional pediatric studies, the pooled sensitivity of Arah2-sIgE at 0.35 kU_A /L cutoff was 83.3% [95% CI 75.6, 88.9] and specificity in diagnosing objective peanut allergy was 83.6% [95% CI 77.4, 88.4]. Compared with 0.1 and 1.0 kU_A /L, this threshold provided the best diagnostic accuracy. At 0.35 kU_A /L, Arah1 and Arah3 had comparable specificity (86.0% and 88.0%, respectively) but significantly lower sensitivity compared with Arah2 (37.0% and 39.1%, respectively; P < .05).

CONCLUSION

sIgE to Arah2 can enhance the certainty of diagnosis and reduce the number of OFC necessary to rule out clinical peanut allergy in unclear cases.

Allergen components in diagnosing childhood hazelnut allergy: Systematic literature review and meta-analysis

BACKGROUND

Hazelnut-specific IgE antibodies (sIgEs) in serum support the diagnosis of hazelnut allergy, but extract-based tests have low diagnostic specificity, commonly leading to over-diagnosis. Measuring sensitization to individual allergen components may enhance the diagnosis of hazelnut allergy. We systematically examined data on diagnostic accuracy of sIgE to commercially available hazelnut components to compare their individual contributions in diagnosing hazelnut allergy.

METHODS

Seven databases were searched for diagnostic studies on patients suspected of having hazelnut allergy. Studies employing component-specific IgE testing on patients whose final diagnosis was determined by oral food challenges were included in the meta-analysis. Study quality was assessed as recommended by Cochrane.

RESULTS

Seven cross-sectional studies and one case-control study were identified, seven presenting data on children (N = 635), and one on a mixed age population. Overall, the diagnostic accuracies of sIgE to both Cor a 9 and Cor a 14 were significantly higher than for Cor a 1-sIgE (P < .05). In children, the specificity of Cor a 14-sIgE at 0.35 kU_A /L cutoff was 81.7% (95% CI 77.1, 85.6), and 67.3% (60.3, 73.6) for Cor a 9-sIgE. The specificities for Cor a 1-sIgE and hazelnut-sIgE were 22.5% (7.4, 51.2) and 10.8% (3.4, 29.8), respectively. The sensitivity of Cor a 1-sIgE (60.2% [46.9, 72.2]) was lower than for hazelnut extract-sIgE (95.7% [88.7, 98.5]), while their specificities did not differ significantly.

CONCLUSION

sIgE to Cor a 14 and Cor a 9 hazelnut storage proteins increases diagnostic specificity in assessing hazelnut allergy in children. The combined use of hazelnut extract and hazelnut storage proteins may improve diagnostic value.

Current Controversies and Future Prospects for Peanut Allergy Prevention, Diagnosis and Therapies

Peanut allergy has increased substantially in the past few decades, both in developed and developing countries. Peanut allergy has become a major public health concern, affecting up to 1 in 50 children, with repercussions for school and airline policies. Recent research findings have shown that, contrary to the long-standing teaching of "delayed" introduction of allergens, early introduction of peanut protein is of benefit as an allergy prevention strategy, especially in high-risk cases. Ideal dose, frequency and duration of "proactive" peanut therapy for maximum protection remain to be determined in order for it to become acceptable and practical on a large scale. Logistics around widespread screening of high-risk patients remain complex. The correct diagnosis of peanut allergy is crucial and diagnostic tests have been fine-tuned in the past 2 decades in order to help differentiate true allergy from false-positive sensitization through cross-reactivity. Component-resolved diagnostics have become routinely available, and the use of basophil activation tests has increased, although standardization and availability remain issues. Future tests, including epitope testing and histamine-release assays, promise to be even more specific in ruling out false positives and reducing the need for incremental food challenges. Stringent peanut avoidance and prompt treatment of reactions remain the cornerstone of treatment. The concept of exposing the allergic body to small amounts of peanut protein in a cautious, orderly, escalating fashion in the form of desensitization has been widely applied in the past 10-15 years, mainly in the research domain, but of late spilling over into every-day practice. However, desensitization does not equate to a cure, and has significant safety concerns and practical ramifications; probably requiring lifelong-controlled peanut ingestion for ongoing protection. Further strategies to enhance the safety and efficacy of immunotherapy are under exploration, many with a non-specific immune-modifying effect. Despite recent advances in peanut allergy, we still need to go back to basics with accurate diagnosis, nutritional counselling, well-organized allergy action plans and accessible emergency kits.

Food Allergy: A Review

Food allergy is an important public health problem that affects children and adults, and it has been increasing in prevalence in the last 2 to 3 decades. The symptoms can vary from mild to severe, and in extreme cases food allergy can lead to anaphylaxis, which is a life-threatening allergic reaction. Currently, there is no cure for food allergy. Management of food allergy includes allergen avoidance or emergency treatment. The eight most common food allergens are eggs, milk, peanuts, tree nuts, soy, wheat, crustacean shellfish, and fish, all of which are frequently consumed in the US. Thus, patients and their families must remain constantly vigilant, which can often be stressful. Moreover, nonallergic food reactions, such as food intolerance, are commonly mistaken as food allergies. This article highlights risk factors, natural history, diagnosis, and management of food allergy. [Pediatr Ann. 2020;49(1):e50-e58.].

Determining Levers of Cost-effectiveness for Screening Infants at High Risk for Peanut Sensitization Before Early Peanut Introduction

IMPORTANCE

Early peanut introduction reduces the risk of developing peanut allergy, especially in high-risk infants. Current US recommendations endorse screening but are not cost-effective relative to other international strategies.

OBJECTIVE

To identify scenarios in which current early peanut introduction guidelines would be cost-effective.

DESIGN, SETTING, AND PARTICIPANTS

This simulation/cohort economic evaluation used microsimulations and cohort analyses in a Markov model to evaluate the cost-effectiveness of early peanut introduction with and without peanut skin prick test (SPT) screening in high-risk infants during an 80-year horizon from a societal perspective. Data were analyzed from April to May 2019.

EXPOSURES

High-risk infants with early-onset eczema and/or egg allergy underwent early peanut introduction with and without peanut SPT screening (100 000 infants per treatment strategy) using a dichotomous 8-mm SPT cutoff value (stipulated in the current US guideline).

MAIN OUTCOMES AND MEASURES

Cost, quality-adjusted life-years (QALYs), net monetary benefit, peanut allergic reactions, severe allergic reactions, and deaths due to peanut allergy.

RESULTS

In the simulated cohort of 200 000 infants and using the base case during the model horizon, a no-screening approach had lower mean (SD) costs ($13 449 [$38 163] vs $15 279 [$38 995]) and higher mean (SD) gain in QALYs (29.25 [3.28] vs 29.23 [3.30]) vs screening but resulted in more allergic reactions (mean [SD], 1.07 [3.15] vs 1.01 [3.02]), severe allergic reactions (mean [SD], 0.53 [1.66] vs 0.52 [1.62]), and anaphylaxis involving cardiorespiratory compromise (mean [SD], 0.50 [1.59] vs 0.49 [1.47]) per individual. In deterministic SPT sensitivity analyses at base-case sensitivity and specificity rates, screening could be cost-effective at a high disutility rate (the negative effect of a food allergic reaction) (76-148 days of life traded) for an at-home vs in-clinic reaction in combination with high baseline peanut allergy prevalence among infants at high risk for peanut allergy and not yet exposed to peanuts. If an equivalent rate and disutility of accidental and index anaphylaxis was assumed and the 8-mm SPT cutoff had 0.85 sensitivity and 0.98 specificity, screening was cost-effective at a peanut allergy prevalence of 36%.

CONCLUSIONS AND RELEVANCE

The results of this study suggest that the current screening approach to early peanut introduction could be cost-effective at a particular health utility for an in-clinic reaction, SPT sensitivity and specificity, and high baseline peanut allergy prevalence among high-risk infants. However, such conditions are unlikely to be plausible to realistically achieve. Further research is needed to define the health state utility associated with reaction location.

How to diagnose food allergy

PURPOSE OF REVIEW

To assess the recent studies that focus on specific immunoglobulin E (sIgE) testing and basophil activation test (BAT) for diagnosing IgE-mediated food allergies.

RECENT FINDINGS

The sIgE to allergen extract or component can predict reactivity to food. The cutoff value based on the positive predictive value (PPV) of sIgE can be considered whenever deciding whether oral food challenge (OFC) is required to diagnose hen's egg, cow's milk, wheat, peanut, and cashew nut allergy. However, PPV varies depending on the patients' background, OFC methodology, challenge foods, and assay methodology. Component-resolved diagnostics (CRD) has been used for food allergy diagnosis. Ovomucoid and omega-5 gliadin are good diagnostic markers for heated egg and wheat allergy. More recently, CRD of peanut, tree nuts, and seed have been investigated. Ara h 2 showed the best diagnostic accuracy for peanut allergy; other storage proteins, such as Jug r 1 for walnut, Ana o 3 for cashew nut, Ses i 1 for sesame, and Fag e 3 for buckwheat, are also better markers than allergen extracts. Some studies suggested that BAT has superior specificity than skin prick test and sIgE testing.

SUMMARY

The sIgE testing and BAT can improve diagnostic accuracy. CRD provides additional information that can help determine whether OFCs should be performed to diagnose food allergy.

IgE testing can predict food allergy status in patients with moderate to severe atopic dermatitis

BACKGROUND

Diagnosing food allergy in patients with atopic dermatitis (AD) is complicated by their high rate of asymptomatic sensitization to foods, which can lead to misdiagnosis and unnecessary food avoidance.

OBJECTIVE

We sought to determine whether food-specific (sIgE) or component immunoglobulin (Ig) E levels could predict allergic status in patients with moderate to severe AD and elevated total IgE.

METHODS

Seventy-eight children (median age, 10.7 years) with moderate to severe AD were assessed for a history of clinical reactivity to milk, egg, peanut, wheat, and soy. The IgE levels for each food and its components were determined by ImmunoCAP. The level and pattern of IgE reactivity to each food and its components, and their ratio to total IgE, were compared between subjects who were allergic and tolerant to each food.

RESULTS

Ninety-one percent of subjects were sensitized, and 51% reported allergic reactivity to at least 1 of the 5 most common food allergens. Allergy to milk, egg, and peanut were most common, and IgE levels to each of these foods were significantly higher in the allergic group. Component IgEs most associated with milk, egg, and peanut allergy were Bos d8, Gal d1, and Ara h2, respectively. The ratio of sIgE to total IgE offered no advantage to sIgE alone in predicting allergy.

CONCLUSION

Specific IgE levels and the pattern of IgE reactivity to food components can distinguish AD subjects allergic vs tolerant to the major food allergens and may therefore be helpful in guiding the clinical management of these patients.

Food Sensitivities: Fact Versus Fiction

Food allergies are on the rise, for reasons that are not fully understood. However, there is a tendency to overestimate their frequency, mostly based on parents' reports or on the assumption that a positive skin or blood IgE test implies the existence of clinically relevant allergy. It is imperative to base food allergy diagnosis on well-defined criteria, avoiding "alternative" tests that are available to the general public. Non-celiac gluten sensitivity is a misnomer and should be abandoned in favor of non-celiac wheat intolerance, an entity suffering from lack of biomarkers and still not convincingly described in children.

Can alternative epitope mapping approaches increase the impact of B-cell epitopes in food allergy diagnostics?

In vitro allergy diagnostics are currently based on the detection of specific IgE binding on intact allergens or a mixture thereof. This approach has drawbacks as it may yield false‐negative and/or false‐positive results. Thus, we reviewed the impact of known B‐cell epitopes of food allergens to predict transience or persistence, tolerance or allergy and the severity of an allergic reaction and to examine new epitope mapping strategies meant to improve serum‐based allergy diagnostics. Recent epitope mapping approaches have been worthwhile in epitope identification and may increase the specificity of allergy diagnostics by using epitopes predominately recognized by allergic patients in some cases. However, these approaches did not lead to discrimination between clinically relevant and irrelevant epitopes so far, since the polyclonal serum IgE‐binding epitope spectrum seems to be too individual, independent of the disease status of the patients. New epitope mapping strategies are necessary to overcome these obstacles. The use of patient‐derived monoclonal antibodies instead of patient sera for functional characterization of clinically relevant and irrelevant epitope combinations, distinguished by their ability to induce degranulation, might be a promising approach to gain more insight into the allergic reaction and to improve serum‐based allergy diagnostics.