The Accuracy of Diagnostic Testing in Determining Tree Nut Allergy: A Systematic Review

Exploring Terebinth Cross-Sensitivity in Individuals with Pistachio Sensitivity

INTRODUCTION

Terebinth (Pistacia terebinthus) belongs to the same botanical family as pistachio (Pistacia vera) and cashew (Anacardium occidentale). Although it is known that there is cross-sensitivity between pistachio and cashew, the cross-sensitivity of terebinth with pistachio or cashew has not been investigated. The objective of our study was to evaluate the sensitivity to terebinth in children with pistachio sensitivity.

METHODS

This study was conducted between September 2021 and June 2022 at Adıyaman University Faculty of Medicine Hospital. It analyzed the results of children who underwent skin prick testing (SPT) for food allergy. Of the 712 food skin prick tests reviewed, 27 children were identified with pistachio sensitivity. Prick tests with commercial extract for cashew and prick-to-prick tests for terebinth were applied to these children.

RESULTS

The median age was two, and 78% were male. Of the children with pistachio sensitivity, 96% demonstrated cross-sensitivity to terebinth and 100% to cashew. There was a strong correlation between the size of SPT responses in pistachio, cashew, and terebinth. Only four children had previously consumed terebinth, and two of these children had allergic reactions.

CONCLUSION

Our study demonstrates a high cross-sensitivity between terebinth, pistachio, and cashew. We recommend that individuals with pistachio or cashew allergy/sensitivity avoid terebinth until tests confirm it is safe to consume. Further studies are needed to demonstrate the clinical significance of this cross-sensitivity and identify the major allergen involved.

Poppy Seed Allergy: Molecular Diagnosis and Cross-Reactivity With Tree Nuts

BACKGROUND

Poppy seed (PS) can be a cause of severe allergic reactions, especially in individuals with concurrent allergy to tree nuts and other seeds, but diagnostic criteria and sensitization patterns are lacking.

OBJECTIVE

To assess the role of PS extract and individual allergens in diagnosing PS allergy and their cross-reactivities with tree nuts and buckwheat.

METHODS

Our retrospective study included 36 PS-sensitized patients; 10 with a positive and 26 with a negative oral food challenge (OFC). We identified individual PS allergens and compared the diagnostic performance of specific IgE (sIgE) to PS extract with its allergens. Cross-reactivities between PS and related allergens from other seeds were assessed by a competitive enzyme-linked immunosorbent assay.

RESULTS

We identified 4 novel PS allergens: Pap s 1 (vicilin), Pap s 1 (27-424) (α-hairpinin), Pap s 2 (legumin), and Pap s 3 (small hydrophilic seed protein). A positive OFC correlated with higher PS-sIgE levels and elevated sIgE levels for the PS allergens, except for Pap s 3. PS and α-hairpinin-sIgE effectively differentiated allergic from tolerant patients, with area under the curve values of 0.95 and 0.94. PS-sIgE >10.00 kUA/L exhibited 90% sensitivity and 73% specificity, whereas α-hairpinin-sIgE >2.60 kUA/L showed 100% sensitivity and 77% specificity. PS vicilin and legumin highly cross-reacted with hazelnut and buckwheat homologs, whereas α-hairpinin-sIgE cross-reacted with the related almond allergen.

CONCLUSIONS

This is the most extensive study on PS allergy to date. PS and α-hairpinin-sIgE are highly sensitive indicators of clinical reactivity to PS, whereas vicilin and legumin-sIgE contribute to concurrent sensitization to hazelnut and buckwheat.

Validation of the NUT CRACKER Diagnostic Algorithm and Prediction for Cashew and Pistachio Co-Allergy

BACKGROUND

Because of the high cross-sensitization among tree nuts, the NUT CRACKER (Nut Co-reactivity-Acquiring Knowledge for Elimination Recommendations) study proposed a diagnostic algorithm to minimize the number of required oral food challenges (OFCs).

OBJECTIVE

To validate the algorithm for cashew and pistachio allergy and determine markers for allergic severity.

METHODS

Patients (n = 125) with a median age of 7.8 (interquartile range, 5.9-11.2) years with suspected tree nut allergy were evaluated prospectively with decision tree points on the basis of skin prick test (SPT), basophil activation test (BAT), and knowledge of the coincidence of allergies. Validation of allergic status was determined by OFC. Markers of clinical severity were evaluated using the combined original and prospective cohort (n = 187) in relationship to SPT, BAT, and Ana o 3-sIgE.

RESULTS

Reactivity to cashew in SPT, BAT, and Ana o 3-sIgE and the incidence of abdominal pain on challenge were significantly higher in dual-allergic cashew/pistachio patients (n = 82) versus single cashew allergic patients (n = 18) (P = .001). All 3 diagnostic tests showed significant inverse correlation with log10 reaction doses for positive cashew OFC. The algorithm reduced overall the total number of OFCs by 72.0%, with a positive predictive value and negative predictive value of 93.0% and 99.0%, respectively. Cashew false-positives were observed primarily in hazelnut-allergic patients (P = .026). In this population, Ana o 3-specific IgE could diagnose cashew allergy with a sensitivity of more than 90% and a specificity of more than 95%.

CONCLUSIONS

The NUT CRACKER diagnostic algorithm was validated and reduced the number of diagnostic OFCs required. Markers for severity phenotypes may guide oral immunotherapy protocols, improving the risk/benefit ratio for patients.

Diagnosis and Management of Pollen Food Allergy Syndrome to Nuts

Oral allergy syndrome or pollen food allergy syndrome (PFAS) represents a common clinical conundrum when the reported trigger food is a tree nut (usually almond or hazelnut) or peanut. The PFAS may give rise to uncertainty about the potential severity of the future reactions, indications for prescribing epinephrine, and the extent of the necessary dietary avoidance. As a food allergy, secondary to cross-reactivity with airborne pollen, PFAS usually manifests toward the end of the first decade of life as contact urticaria of the oropharyngeal mucous membranes. Molecular allergology facilitates diagnosis and risk stratification by establishing the profile of sensitization. Exclusive sensitization to pathogenesis-related proteins family 10 (PR10) and profilins indicates that signs and symptoms are due to PFAS, whereas sensitization to seed storage proteins with or without sensitization to PR10 and profilins may indicate a more severe primary nut allergy phenotype. Management relies on avoidance of the specific nut trigger, advice on the likelihood of more severe local or systemic symptoms, and treatment of reactions according to the severity. Future studies are needed to better delineate the risk of systemic reactions in individuals with nut PFAS and to establish the role of food or pollen allergen immunotherapy for the prevention or moderation of this condition.

Jug r 1 sensitization in 0- to 35-month-old children with egg, milk, or wheat sensitization

Background

The incidence of tree nut allergies in children is increasing, with walnut allergy being the most common in the United States and Japan. Allergic reactions, including anaphylaxis, frequently occur at the first intake of tree nuts, suggesting prior sensitization.

Objective

Our aim was to identify which children should be considered for workup for preexisting sensitization.

Methods

Juglans regia (Jug r) 1-specific IgE screening for 0- to 35-month-old children who had a positive specific IgE result for egg white, milk, or wheat and had never ingested walnuts was conducted at a food allergy referral hospital between November 2018 and December 2022. Clinical data regarding age; sex; allergic disease complications; and egg, milk, or wheat allergy were examined retrospectively.

Results

The rate of Jug r 1-specific IgE positivity (level > 0.34 kUA/L) of 205 children (125 of whom were boys) was 9.8%, with a median Jug r 1-specific IgE level of 12.5 kUA/L in patients with a positive test result. Eczema was observed in 119 patients (58%). The rate of Jug r 1-specific IgE positivity was significantly higher in the eczema-positive group (15.1% [18 of 119]) than in the eczema-negative group (2.3% [2 of 86]) (P = .002). In the eczema-positive group, the rates of Jug r 1-specific IgE positivity per sensitized antigen were 13.7% for egg, 17.0% for milk, and 17.1% for wheat. The rate of Jug r 1-specific IgE positivity was significantly higher in the group with severe eczema (26.6% [17 of 64]) than in the group with nonsevere eczema (1.8% [1 of 55]) (P < .001).

Conclusion

Even in children younger than 3 years, 15% of children with eczema and egg, milk, or wheat sensitization were sensitized to Jug r 1.

The Value of Current Laboratory Tests in Diagnosing Food, Venom, and Drug Allergies

An accurate diagnosis of IgE-mediated allergies is necessary to inform risk management for severe allergic reactions including anaphylaxis for food, venom, and drug allergies. The most widely available laboratory test for allergy is serum-specific IgE testing, which is routinely used for food allergy and insect sting allergy. Testing for specific IgE is limited by high sensitivity and low specificity, resulting in concern regarding overdiagnosis. Testing of allergen components has led to improved diagnosis for some food and venom allergens. Additional options for laboratory tests, such as epitope analysis, basophil activation, and mast cell activation, are being investigated for their potential to optimize diagnosis and provide predictors for reaction severity and treatment response. In contrast, laboratory testing for drug allergy is more limited because to date, there are no well-validated commercial assays in the United States. Furthermore, it is important to diagnose delayed reactions to medications, because these also significantly affect decision-making regarding therapeutic options for infectious disorders. Reliable tests for both immediate and delayed drug hypersensitivity are much needed, because drug allergy labels can significantly limit treatment options for patients. Research in this area is emerging.

Natural History of Hazelnut Allergy and Current Approach to Its Diagnosis and Treatment

Hazelnut allergy is the most prevalent type of nut allergy in Europe, with symptoms that can range from mild, such as hives and itching, to severe, such as anaphylaxis, particularly in patients who are sensitized to highly stable allergens, such as storage proteins. Compared to other types of food allergies, allergies to tree nuts, including hazelnuts, tend to persist throughout life. Although symptoms can appear in early childhood, they often continue into adulthood, with a minority of cases improving during adolescence. Currently, there is no curative treatment available for hazelnut allergy, and patients must adhere to a restrictive diet and carry autoinjective epinephrine. However, oral allergen immunotherapy (AIT) is a promising treatment option. Patients can be categorized based on their risk for severe reactions using various clinical, in vivo, and in vitro tests, including component-resolved diagnosis and oral food challenge. This review aims to provide an overview of the current knowledge of the natural history of hazelnut allergy and new approaches for its diagnosis and management.

Tree nut allergy: a systematic review

PURPOSE OF REVIEW

Systematic scoping review, focusing on randomized clinical trials of recent research addressing tree nut allergy.

RECENT FINDINGS

This review addresses published, unpublished, and re-analyzed studies on tree nut allergy definition, epidemiology, etiology, diagnosis, prognosis, and therapy.

SUMMARY

The importance of tree nut allergy spans nations, economies, and cultures. While broad themes in epidemiology, etiology, diagnosis, prognosis, and therapy are emerging, the next major advance in tree nut allergy will require large, robust studies to deliver results important to patients and families.

Macadamia nut-specific IgE levels for predicting anaphylaxis

BACKGROUND

Despite the high risk of anaphylaxis in patients with a macadamia nut allergy (MdA), little is known about the significance of macadamia nut-specific immunoglobulin E (Md-sIgE). Thus, this study aimed to investigate the utility of Md-sIgE for predicting anaphylaxis.

METHODS

Children with suspected MdA who visited our hospital were included. MdA was defined as either failing the 3-g macadamia nut (Md) oral food challenge (OFC) or confirming obvious immediate symptoms following Md ingestion. Non-MdA was defined as passing the 3-g Md OFC.

RESULTS

A total of 41 children (29 [71%] males) with a median age of 7.7 years were included. The median Md-sIgE level was 2.23 kU_A /L. Among the 21 children diagnosed with MdA, eight and 13 children did (An group) and did not (non-An group) develop anaphylaxis. Twenty children were included in the non-MdA group. The Md-sIgE level was significantly higher in the An group relative to the others (7.97 vs. 1.92 kU_A /L, p < .001). Furthermore, the Md-sIgE level was significantly higher in the An group than in the non-An group (7.97 vs. 1.92 kU_A /L, p = .02). However, there was no significant difference in the Md-sIgE between the non-An and non-MdA groups (1.92 vs. 1.90 kU_A /L, p > .99). The area under the curve for predicting anaphylaxis in Md-sIgE was 0.92 (95% CI: 0.83-1.00), and the optimal cut-off value was 3.76 kU_A /L.

CONCLUSION

Md-sIgE levels were useful in predicting anaphylaxis. Above the cut-off value, we emphasize paying careful attention to the risk of anaphylaxis.

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.

Ana o 3 sIgE and diagnostic algorithms reduce cost of cashew allergy diagnosis in children compared with skin prick test: A cost comparison analysis

BACKGROUND

In the absence of a clear clinical history of reaction, diagnosis of cashew allergy using skin prick tests (SPT) or cashew-specific IgE requires a high number of oral food challenges (OFC). By using Ana o 3 sIgE alone, or a two-step diagnostic algorithm using cashew sIgE followed by Ana o 3 sIgE, there is a reduced need for OFC. We aimed to perform a cost comparison for both of these approaches compared with cashew SPT alone.

METHODS

Pooled individual-level data from 6 studies were used to determine diagnostic accuracy and OFC rate. Two studies used cashew SPT (n = 567, 198 allergic), with 95% positive and negative predictive values of ≥12 mm and <3 mm. Four studies were included in the pathways for Ana o 3 sIgE alone or a 2-step algorithm incorporating cashew and Ana o 3 sIgE (n = 271, 156 allergic). Cut-offs used were ≥8.5kUA/L and ≤0.1kUA/L for cashew sIgE and ≥0.35kUA/L and ≤0.1kUA/L for Ana o 3 sIgE. Costs were constructed based on unit prices from hospital inpatient admissions, expenses incurred by families, individual patient data on allergic reaction types and rates, and adrenaline autoinjector carriage, applying a health system perspective.

RESULTS

Modeled data through the Ana o 3 pathway resulted in a 46.43% cost reduction (€307,406/1000 patients) compared with using cashew SPT alone (€573,854/1000 patients). The 2-step algorithm resulted in a 44.94% cost reduction compared with SPT alone (€315,952.82/1000 patients). Both the Ana o 3 pathway and 2-step algorithm resulted in a 79%-80% reduction in OFCs compared with SPT.

CONCLUSIONS

Using Ana o 3 as a standalone test for cashew allergy diagnosis or a 2-step algorithm incorporating cashew sIgE and Ana o 3 sIgE is accurate and results in a large reduction in both OFCs and health system costs compared with cashew SPT alone.

Diversities of allergic pathologies and their modifiers: Report from the second DGAKI-JSA meeting

In October 2021, researchers from the German Society of Allergy and Clinical Immunology (DGAKI) and from the Japanese Society of Allergology (JSA) focused their attention on the pathological conditions and modifiers of various allergic diseases. Topics included 1) the pathophysiology of IgE/mast cell-mediated allergic diseases; 2) the diagnosis and prevention of IgE/mast cell-mediated diseases; 3) the pathophysiology, diagnosis, and treatment of eosinophilic airway diseases; and 4) host-pathogen interaction and allergic diseases. This report summarizes the panel discussions, which highlighted the importance of recognizing the diversity of genetics, immunological mechanisms, and modifying factors underlying allergic diseases.

Molecular diagnosis contribution for personalized medicine

PURPOSE OF REVIEW

The purpose of the current review is to highlight the most recent findings in molecular allergy and its applicability in precision medicine for allergic patients.

RECENT FINDINGS

Molecular allergy provides useful information in areas of respiratory allergy (house dust mites, pet dander and pollen allergy), food allergy (tree nuts, peanuts, fruits and vegetables), hymenoptera venom allergy and others, in order to improve management of patients. Regional differences in sensitization profiles, assay characteristics and interpretation of molecular sensitization in relation to whole extracts and total immunoglobulin E need to be taken into account. Studies of the impact of such strategies are needed.

SUMMARY

Molecular allergy diagnosis represents a major contribution for personalized medicine. It aids in the assesment of risk prediction, disease severity, genuine/cross-reactive sensitization, and finally to apply precise management strategies.

Multiplex component-based allergen macroarray test is useful to predict clinical reactivity to tree nuts in children

BACKGROUND

In tree nut (TN) allergy, singleplex tests showed the diagnostic utility of rAna o 3, rCor a 14/nCor a 9, and nJug r 1/nJug r 4 for cashew/pistachio, hazelnut, and walnut allergies, respectively. However, disadvantages of the tests include high costs and excessive blood sampling in multi-sensitized patients, and a limited number of components. We investigated the utility of a multiplex macroarray (i.e., the ALEX² test) in TN allergy.

METHODS

In 169 children, skin prick test, the component- and extract-specific IgEs of TNs were investigated for clinical reactivity and tolerance.

RESULTS

The predictors (AUC = 0.962-0.749) of clinical reactivity to cashew, pistachio, hazelnut, and walnut were rPis v 1/rAna o 3, rPis v 1/rAna o 3/nPis v 2/nPis v 3, rCor a 14/nCor a 11/nCor a 9, and nJug r 1/nJug r 2/nJug r 6/nJug r 4, respectively. More than 93% of the patients with clinical reactivity to pistachio/cashew, hazelnut and walnut had positivity of (≥0.3 kU_A/L) rPis v 1/rAna o 3, rCor a 14 and nJug r 1/nJug r 2, respectively. The highest accuracies of clinical reactivity to culprit nut were obtained with combination of rPis v 1, sIgE and SPT positivities for cashew/pistachio, rPis v 1 ≥ 1.0 kU_A/L for pistachio, rCor a 14 ≥ 1.0 kU_A/L for hazelnut and combination of nJug r 1 and nJug r 2 positivities for walnut, respectively. Also, higher concentrations of rPis v 1 (≥15.0 kU_A/L), rCor a 14 (≥5.0 kU_A/L) and nJug r 1/nJug r 2 (≥15.0 kU_A/L) had %100 specificity and PPV in predicting clinical reactivity to cashew, hazelnut and walnut, respectively.

CONCLUSIONS

Multiplex macroarray test is useful and reliable in the diagnosis of TN allergy in children, confirms and expands existing knowledge, and can be used as a stand-alone tool in the bottom-up diagnostic approach.

Patterns of Clinical Reactivity in a Danish Cohort of Tree Nut Allergic Children, Adolescents, and Young Adults

Background

Tree nut allergy is associated with severe reactions and poly-sensitization to other nuts and peanuts often occurs. There are regional differences in sensitization profiles that result in differences in clinical presentation. Denmark is located in a birch pollen endemic area, which could influence the allergy patterns due to pollen cross-sensitization.

Objective

This study aimed to investigate patterns of sensitization and clinical reactivity to tree nuts and peanuts and threshold levels for oral food challenges (OFCs) in a Danish cohort of tree nut allergic children, adolescents, and young adults.

Methods

Forty tree nut allergic subjects were assessed for clinical reactivity to six nuts, i.e., hazelnut, walnut, pistachio, cashew, almond, and peanut, by OFCs or convincing medical history of an immediate allergic reaction or tolerance. Clinical presentation and allergen-specific immunoglobulin E (sIgE) levels together with eliciting dose and rescue medication in OFCs were furthermore assessed.

Results

Allergy to two or more tree nuts was observed in most cases. Hazelnut-walnut dual allergy was common but not exclusively observed as concomitant allergies. Allergy to cashew was coincided in all but one of the assessed subjects with pistachio allergy. Half of all assessed subjects were allergic to peanuts. Oral symptoms followed by a skin reaction were the most common symptomatology that lead to OFC cessation and subjects often presented with symptoms from two or more organ systems. OFC threshold levels were within the same range, but cashew was distinguished from other nuts by causing allergic symptoms at the lowest dose. Clinical reactivity and the allergy patterns were to some extent reflected by sIgE levels and by correlations in sIgE between the nuts.

Conclusions

In this Northern European cohort, subjects with clinically relevant tree nut allergy were generally allergic to two or more tree nuts and close to half of them also to peanuts. There were two distinct and independent allergic phenotypes; the majority of hazelnut allergic subjects were also allergic to walnut, and all but one subject with cashew allergy were dual allergic to pistachio. These findings are consistent with a strong sIgE correlation between hazelnut and walnut and a close to total sIgE correlation between cashew and pistachio.

Tree nut introduction in a peanut-allergic child: To eat, to screen, or to avoid?

There is no defined standard of care around tree nut introduction in a peanut-allergic child, and the role of screening prior to tree nut introduction is controversial. There is some evidence that peanut-allergic children are at increased risk of tree nut allergy, with approximately 23-68% of children with co-existent peanut/tree nut allergy. In some studies, it has been shown that tree nut allergy in children has the potential to be a severe allergy. However, this appears to be age-specific as infant anaphylaxis in general tends to be milder, and there has been no fatality reported on the first ingestion of an allergen in infancy. Familial hesitancy has been identified as a possible condition for undertaking screening tests prior to allergen introduction. Indeed, there has been limited evidence that caregiver hesitancy may exist in peanut-allergic families with tree nut introduction. However, pre-emptive screening has the potential to overdiagnose tree nut allergy and delay introduction (which could paradoxically increase risk). As a result, the decision is best made in the context of shared decision-making and patient preference-sensitive care.

Prevalence and early-life risk factors for tree nut sensitization and allergy in young adults

BACKGROUND

Tree nut allergy may cause anaphylaxis. There are limited population-based studies on prevalence and early-life risk factors.

METHODS

We evaluated the prevalence of reported symptoms and allergic sensitization to tree nuts at age 24 years in the BAMSE population-based cohort study and assessed early-life factors associated with the development of tree nut allergy. We estimated tree nut allergy prevalence, by analysing questionnaire data on tree nut ingestion and symptoms at age 12, 16 and 24 years, and IgE sensitization at age 24 years to hazelnut, walnut, pecan, cashew, pistachio, Brazil nut, almond extracts and allergen molecules Cor a 1, 9, 14 (hazelnut), Jug r 1 (walnut) and Ana o 3 (cashew). We evaluated eczema, asthma, food allergies, inherited risk of allergy and gender as potential early-life risk factors.

RESULTS

Data were available for 2215/4089 (54%) BAMSE study participants, for estimation of the prevalence of tree nut sensitization (21.2%), tree nut allergy symptoms (9.8%) and combined sensitization and symptoms (7.9%, 2.1% for storage protein sensitization and symptoms, 4.3% for any sensitization and non-mild symptoms). Sixty-three per cent of sensitized individuals (295/470) were asymptomatic, but only 76/470 (16%) storage protein sensitized individuals. Egg allergy (OR_adj 8.50 95% CI 2.15-33.6), eczema (OR_adj 2.53 95% CI 1.21-5.32) and asthma (OR_adj 5.59 95% CI 2.35-13.3)) at pre-school age were associated with future development of tree nut symptoms and storage protein sensitization. At age 24 years, tree nut allergy was associated with current eczema and with markers of current asthma severity. Sensitization to storage proteins was more strongly associated with symptoms than sensitization to whole extract for all tree nuts evaluated.

CONCLUSIONS

In this Swedish cohort, we found tree nut whole extract sensitization is common but usually asymptomatic. Storage protein sensitization is a more reliable indicator of tree nut symptoms. Tree nut allergy is associated with early onset, persistent and severe atopic disease.