Basophil activation tests for the diagnosis of food allergy in children

Basophil activation test in the food allergy clinic: its current use and future applications

INTRODUCTION

The basophil activation test (BAT) has shown evidence of high sensitivity and high specificity to support the diagnosis of IgE-mediated allergy. It is a functional test that uses live cells analyzed by flow cytometry and thus needs to be performed within 24h of blood collection. BAT has shown to be reproducible and reliable when tested in a clinical diagnostic laboratory with standardized protocols and flow cytometry settings.

AREAS COVERED

In this review, we summarize the evidence to support clinical use of BAT and the next steps required for clinical implementation for an improve clinical care for patients with suspected IgE-mediated food allergy.

EXPERT OPINION

BAT has recently been included in Clinical Guidelines of Food Allergy Diagnosis and its implementation in clinical practice depends largely on availability. Proposed clinical applications of the BAT include: distinction between food allergy and asymptomatic IgE sensitization; determination of food allergic status to peanut, tree nuts and seeds in polysensitized children; evaluation of tolerance to baked egg and baked milk in egg and milk allergic children; identification of patients at high-risk of severe allergic reactions; monitoring for spontaneous resolution of food allergy; confirmation of eligibility for specific treatments of food allergy; prediction and monitoring of response to immunomodulatory treatments.

Increased CD123 + HLA-DR- Granulocytes in Allergic Rhinitis and Influence of Allergens on Expression of Cell Membrane Markers

BACKGROUND

It is reported that CD123 + HLA-DR- cells in PBMC are basophils, and CD203c, CD63, and FcεRI molecules are activation markers of basophils. However, little is known of CD123 + HLA-DR-cells in blood granulocytes.

OBJECTIVE

To investigate the presence of CD123 + HLA-DR- cells in the blood granulocytes and peripheral PBMC of patients with allergic rhinitis (AR), as well as the impact of allergens on the cell membrane markers of basophils.

METHODS

Flow cytometry was used to detect the expression of the membrane molecules.

RESULTS

While CD123 + HLA-DR- PBMCs are representative of basophils, their presence did not significantly change in patients with AR. In contrast, both the percentage and number of CD123 + HLA-DR- granulocytes, which make up only up to 50% of basophils, were significantly increased in patients with seasonal (sAR) and perennial AR (pAR). CD63+, CD203c+, and FcεRIα+ cells within CD123 + HLA-DR- granulocytes also showed enhanced activity in patients with AR. Allergen extracts from house dust mite allergen extract (HDME) and Artemisia sieversiana wild extract further increased the number of CD123 + HLA-DR- cells in granulocytes of sAR and pAR patients, as well as in PBMCs of pAR patients.

CONCLUSIONS

The use of CD123 + HLA-DR- granulocytes and PBMC may not be sufficient for diagnosing AR. Allergens could potentially contribute to the development of AR by influencing the number of CD123 + HLA-DR- cells, as well as the expression of CD63, CD203c, and FcεRIαin these cells.

Food Allergy

Food allergy is a growing health problem affecting both pediatric and adult patients. Food allergies are often immunoglobulin E (IgE) mediated but other food-induced non-IgE-mediated diseases exist. Diagnosis of food allergy relies on the combination of clinical and reaction history, skin and IgE testing as well as oral food challenges. Although oral immunotherapy has been able to achieve sustained unresponsiveness in some patients, no cure for food allergies has been found to date. Avoidance of the inciting food as well as availability of epinephrine autoinjectors remains the mainstay of treatment.

Management of food allergy based on oral food challenge

PURPOSE OF REVIEW

Food allergy is a growing health problem that affects both patients and society in multiple ways. Despite the emergence of novel diagnostic tools, such as component-resolved diagnostics (CRD) and basophil activation tests (BAT), oral food challenge (OFC) still plays an indispensable role in the management of food allergies. This review aimed to highlight the indications and safety concerns of conducting an OFC and to provide insights into post-OFC management based on recent findings.

RECENT FINDINGS

Standardized OFC protocols have regional diversification, especially in Japan and Western countries. Recent studies suggested that the interval between doses should be at least more than an hour. Furthermore, applying a stepwise method tailored to the patient's specific immunoglobulin E level and history of anaphylaxis seems to mitigate these risks. Recent surveys have shown that, following a positive OFC, options other than strict avoidance are also selected.

SUMMARY

OFC serves diverse purposes, yet the risks it carries warrant caution. The stepwise protocol appears promising for its safety. Subthreshold consumption following OFC shows potential; however, further research on its efficacy and safety is required. Management following OFC should be tailored and well discussed between clinicians and patients.

Combining avidin with CD63 improves basophil activation test accuracy in classifying peanut allergy

BACKGROUND

Conventional basophil activation tests (BATs) measure basophil activation by the increased expression of CD63. Previously, fluorophore-labeled avidin, a positively-charged molecule, was found to bind to activated basophils, which tend to expose negatively charged granule constituents during degranulation. This study further compares avidin versus CD63 as basophil activation biomarkers in classifying peanut allergy.

METHODS

Seventy subjects with either a peanut allergy (N = 47), a food allergy other than peanut (N = 6), or no food allergy (N = 17) were evaluated. We conducted BATs in response to seven peanut extract (PE) concentrations (0.01-10,000 ng/mL) and four control conditions (no stimulant, anti-IgE, fMLP (N-formylmethionine-leucyl-phenylalanine), and anti-FcεRI). We measured avidin binding and CD63 expression on basophils with flow cytometry. We evaluated logistic regression and XGBoost models for peanut allergy classification and feature identification.

RESULTS

Avidin binding was correlated with CD63 expression. Both markers discriminated between subjects with and without a peanut allergy. Although small by percentage, an avidin+ /CD63- cell subset was found in all allergic subjects tested, indicating that the combination of avidin and CD63 could allow a more comprehensive identification of activated basophils. Indeed, we obtained the best classification accuracy (97.8% sensitivity, 96.7% specificity) by combining avidin and CD63 across seven PE doses. Similar accuracy was obtained by combining PE dose of 10,000 ng/mL for avidin and PE doses of 10 and 100 ng/mL for CD63.

CONCLUSIONS

Avidin and CD63 are reliable BAT activation markers associated with degranulation. Their combination enhances the identification of activated basophils and improves the classification accuracy of peanut allergy.

The role of basophil activation test and component-resolved diagnostics in the workup of egg allergy in children at low risk for severe allergic reactions: A real-life study

BACKGROUND

The gold standard for diagnosing egg allergy in children is the oral food challenge (OFC). However, OFCs are time-consuming and risky procedures. Our study aimed to evaluate the utility of the basophil activation test (BAT) and component-resolved diagnostic in the diagnostic workup of children with egg allergy.

METHODS

Overall, 86 children aged 6 months to 17 years, suspected of egg allergy, underwent OFC with boiled egg according to international standardized protocols. BAT and specific immunoglobulin E (sIgE) testing to component egg proteins (Gal d 1-4) were also performed.

RESULTS

Of the 22 children who reacted to boiled egg, only one experienced anaphylaxis during the challenge. BAT was performed in samples obtained by 75 of the 86 patients of our cohort. Egg white and yolk protein extracts induced CD63 upregulation in the egg-allergic (EA) children compared with sensitized children that tolerated boiled egg (we registered an overall mean of CD63 expression in the EA population of 44.4% [SD 34.1] for egg white and 34.7% [SD 31.3] for egg yolk vs. 12.5% [SD 19.1] and 10.0% [SD 16.0] in sensitized children). BAT could discriminate between true egg allergy and egg sensitization in our population. As a second-line diagnostic step, the positivity of BAT for egg white or Gal d 1-sIgE resulted in a 40.9% OFC reduction, especially for those with a positive outcome.

CONCLUSION

The BAT may be implemented in the diagnostic workup of egg allergy in children and, in a stepwise approach, separately or combined with Gal d 1-sIgE, may predict the allergic status and reduce the number of positive OFCs in children with egg allergy at low risk for severe reactions.

The combination of Ara h 2-sIgE and basophil activation test could be an alternative to oral food challenge in cases of suspected peanut allergy

BACKGROUND

Most children with peanut sensitisation do not have a clinical peanut allergy (PA). Oral food challenge (OFC) is then necessary to diagnose PA and assess the reactive dose of the allergen. However, OFC is laborious to perform, expensive and stressful. We evaluated whether in vitro tests, such as basophil activation test (BAT), allergen-specific IgE (sIgE) and their combination, could be used to replace OFC for the diagnosis of PA in children.

METHODS

Ninety-one patients aged 6 months to 18 years with suspected PA were prospectively recruited. These patients then underwent an OFC to assess PA. Whole peanut-sIgE, Ara h 2-sIgE, Ara h 8-sIgE and %CD63+ basophils (CCR3+ /SCClow ) to peanut measured by BAT were investigated for PA diagnosis.

RESULTS

Forty-one patients had a positive peanut OFC, and the remaining 50 were only sensitised. All patients with Ara h 2-sIgE >7 kUA /L were allergic to peanut. A threshold of 6% for activated basophils yielded a sensitivity of 95% and a specificity of 54%. All patients with Ara h 2-sIgE ≤7 kUA /L and BAT ≤6% (n = 22) had a negative OFC except for one who presented an oral syndrome due to PR-10 sensitisation.

CONCLUSIONS

We have shown that Ara h 2-sIgE >7 kUA/L is a discriminating threshold for the diagnosis of PA. Furthermore, when Ara h 2-sIgE ≤7 kUA/L and BAT ≤6%, patients do not need to adjust their diet and, thus, do not need an OFC.

The future of food allergy: Challenging existing paradigms of clinical practice

The field of food allergy has seen tremendous change over the past 5-10 years with seminal studies redefining our approach to prevention and management and novel testing modalities in the horizon. Early introduction of allergenic foods is now recommended, challenging the previous paradigm of restrictive avoidance. The management of food allergy has shifted from a passive avoidance approach to active interventions that aim to provide protection from accidental exposures, decrease allergic reaction severity and improve the quality of life of food-allergic patients and their families. Additionally, novel diagnostic tools are making their way into clinical practice with the goal to reduce the need for food challenges and assist physicians in the-often complex-diagnostic process. With all the new developments and available choices for diagnosis, prevention and therapy, shared decision-making has become a key part of medical consultation, enabling patients to make the right choice for them, based on their values and preferences. Communication with patients has also become more complex over time, as patients are seeking advice online and through social media, but the information found online may be outdated, incorrect, or lacking in context. The role of the allergist has evolved to embrace all the above exciting developments and provide patients with the optimal care that fits their needs. In this review, we discuss recent developments as well as the evolution of the field of food allergy in the next decade.

Food Allergy

Food allergy is a growing health problem affecting both pediatric and adult patients. Food allergies are often immunoglobulin E (IgE) mediated but other food-induced non-IgE-mediated diseases exist. Diagnosis of food allergy relies on the combination of clinical and reaction history, skin and IgE testing as well as oral food challenges. Although oral immunotherapy has been able to achieve sustained unresponsiveness in some patients, no cure for food allergies has been found to date. Avoidance of the inciting food as well as availability of epinephrine autoinjectors remains the mainstay of treatment.

Basophil activation test has high reproducibility and is feasible in the clinical setting

BACKGROUND

The basophil activation test (BAT) has high accuracy to diagnose peanut allergy and can reduce the need for oral food challenges (OFC); however, so far it has not been incorporated in clinical practice.

METHODS

We assessed the reproducibility of BAT within the same laboratory and between two different laboratories and the feasibility of using BAT in the clinical setting.

RESULTS

One hundred and two children being assessed for peanut allergy were tested on BAT (72 allergic, 30 sensitized tolerant). There was little internal variation (coefficient of variation <15%) in the BAT and a very strong correlation (Rs  > .95) between BAT performed across laboratories. The 2 BAT methods were strongly correlated but not interchangeable. In the cases of discrepancy, our in house BAT method was 100% accurate. BAT was feasible and well-accepted by clinicians: no patient with positive BAT was referred for OFC, leading to reduction in the number of OFC required. Twenty one percent of patients who underwent OFC reacted to peanut. A negative BAT also encouraged the performance of OFC in sensitized children who would otherwise be considered allergic, 50% of whom did not react and incorporated peanut in the diet.

CONCLUSIONS

The BAT is a robust test that can reliably be transferred between laboratories; however, different BAT methods are not interchangeable. BAT was well integrated in the clinical decision-making process in a specialized center.

Biomarkers in oral immunotherapy

Food allergy (FA) is a global health problem that affects a large population, and thus effective treatment is highly desirable. Oral immunotherapy (OIT) has been showing reasonable efficacy and favorable safety in most FA subjects. Dependable biomarkers are needed for treatment assessment and outcome prediction during OIT. Several immunological indicators have been used as biomarkers in OIT, such as skin prick tests, basophil and mast cell reactivity, T cell and B cell responses, allergen-specific antibody levels, and cytokines. Other novel indicators also could be potential biomarkers. In this review, we discuss and assess the application of various immunological indicators as biomarkers for OIT.

IgE-Mediated food allergy: Current diagnostic modalities and novel biomarkers with robust potential

Food allergy (FA) is a serious public health issue afflicting millions of people globally, with an estimated prevalence ranging from 1-10%. Management of FA is challenging due to overly restrictive diets and the lack of diagnostic approaches with high accuracy and prediction. Although measurement of serum-specific antibodies combined with patient medical history and skin prick test is a useful diagnostic tool, it is still an imprecise predictor of clinical reactivity with a high false-positive rate. The double-blind placebo-controlled food challenge represents the gold standard for FA diagnosis; however, it requires large healthcare and involves the risk of acute onset of allergic reactions. Improvement in our understanding of the molecular mechanism underlying allergic disease pathology, development of omics-based methods, and advances in bioinformatics have boosted the generation of a number of robust diagnostic biomarkers of FA. In this review, we discuss how traditional diagnostic modalities guide appropriate diagnosis and management of FA in clinical practice, as well as uncover the potential of the latest biomarkers for the diagnosis, monitoring, and prediction of FA. We also raise perspectives for precise and targeted medical intervention to fill the gap in the diagnosis of FA.

Exploring the role of basophil activation test in diagnosis of Dermatophagoides farinae sensitization and evaluation of therapeutic efficacy of subcutaneous immunotherapy in children

OBJECTIVE

It aims to detect basophil activation ratio (%CD63⁺ ) in peripheral blood of children with allergic asthma and rhinitis by using Flow cytometry (FCM) , so as to analyze the application values and clinical relevance of the Basophil Activation Test (BAT) in diagnosis of Dermatophagoides farinae (Derf) sensitization and monitoring therapeutic efficacy of subcutaneous immunotherapy (SCIT).

METHODS

It was a prospective study. From the newly diagnosed children with asthma and rhinitis in our pediatric clinic, 39 patients diagnosed Derf sensitization and 15 patients not allergic to Derf were enrolled; another 4 healthy children were taken as control group. Using Derf extracts in concentration of 1 μg/ml, 10 μg/ml and 100 μg/ml as the stimulus, BAT results were expressed as %CD63⁺ in diagnosis of Derf sensitization and its correlation with skin prick tests (SPT), serum total IgE (tIgE), specific IgE (sIgE), sIgE/tIgE, specific IgG4 (sIgG4), FEV1%pred in pulmonary ventilation function, exhaled nitric oxide (FeNO), children asthma control test (C-ACT) and visual analogue scale (VAS) were observed. In sensitization group, %CD63⁺ , sIgG4 and clinical indicators were detected again from patients who had received SCIT to analyze their internal connections.

RESULTS

The average levels of %CD63⁺ in three concentrations showed an increasing concentration-dependent trend overall. %CD63⁺ in sensitization group was significantly higher than that in the other two groups. The analysis of ROC for Derf sensitization showed the area under the curve (AUC) for BAT in three concentrations were higher than that for sIgE whose AUC is 0.893. %CD63⁺ was positively correlated with SPT grade, sIgE, sIgE/tIgE and VAS, and negatively correlated with C-ACT. In patients receiving SCIT, %CD63⁺ became lower and sIgG4 level became higher than pretreatment. There was no obvious change in sIgG4 in those who hadn't received SCIT.

CONCLUSIONS

BAT is a reliable and non-invasive tool for diagnosis of Derf sensitization in children with asthma and rhinitis. CD63-based BAT has clinical value to monitor outcome of SCIT, and the change of basophil activation is inherently related to induction of sIgG4.

Clinical and Translational Significance of Basophils in Patients with Cancer

Despite comprising a very small proportion of circulating blood leukocytes, basophils are potent immune effector cells. The high-affinity receptor for IgE (FcɛRI) is expressed on the basophil cell surface and powerful inflammatory mediators such as histamine, granzyme B, and cytokines are stored in dense cytoplasmic granules, ready to be secreted in response to a range of immune stimuli. Basophils play key roles in eliciting potent effector functions in allergic diseases and type 1 hypersensitivity. Beyond allergies, basophils can be recruited to tissues in chronic and autoimmune inflammation, and in response to parasitic, bacterial, and viral infections. While their activation states and functions can be influenced by Th2-biased inflammatory signals, which are also known features of several tumor types, basophils have received little attention in cancer. Here, we discuss the presence and functional significance of basophils in the circulation of cancer patients and in the tumor microenvironment (TME). Interrogating publicly available datasets, we conduct gene expression analyses to explore basophil signatures and associations with clinical outcomes in several cancers. Furthermore, we assess how basophils can be harnessed to predict hypersensitivity to cancer treatments and to monitor the desensitization of patients to oncology drugs, using assays such as the basophil activation test (BAT).

The Basophil Activation Test for Clinical Management of Food Allergies: Recent Advances and Future Directions

The basophil activation test (BAT) is an ex vivo functional assay that measures by flow cytometry the degree of basophil degranulation after stimulation with an allergen. In recent years, there has been an increased interest in the diagnostic value of the BAT as it has the potential to mimic the clinical phenotype of sIgE sensitized patients, in contrast to allergen-specific IgE levels. This diagnostic potential would be of particular interest for food allergies present early in life such as peanut, cow’s milk and eggs, which require an expensive, time-consuming and patient unfriendly oral food challenge (OFC) for diagnosis. However, routine applications of the BAT for clinical use are not yet feasible due to the lack of standardized protocols and large clinical validation studies. This review will summarize the current data regarding the application of the BAT in food allergy (FA) for cow’s milk, egg and peanut, being the most common causes of FA in children. Additionally, it will discuss the hurdles for widespread clinical use of the BAT and possible future directions for this diagnostic procedure.

Combinatorial advantage of Ses i 1-specific IgE and basophil activation for diagnosis of sesame food allergy

BACKGROUND

The prevalence of sesame food allergy (SFA) is increasing worldwide with the potential of anaphylactic reactions upon exposure. Utility of specific component IgE testing as an alternative to the oral food challenge (OFC), the diagnostic standard, is being investigated.

METHODS

Patients (n = 42) with suspected SFA completed an open OFC to sesame. Diagnostic testing included serum levels of Ses i 1-specific IgE, skin prick test with high-protein extract, and basophil reactivity (% induced CD63 expression) for each patient. The diagnostic utility of these tests was evaluated at a 95% sensitivity, with the outcome measure being the number of OFCs required.

RESULTS

Twenty-seven patients (64%) were diagnosed with SFA. Ses i 1 IgE differed significantly between allergic and tolerant patients (p = .0001). ROC curve analysis for Ses i 1 IgE yielded an AUC of 0.88 ± 0.05. Levels of Ses i 1 IgE correlated to induced CD63+ expression on basophils (p = .0001). Ses i 1 IgE was not sufficiently robust as a single step for diagnosis. Used concurrently, BAT and Ses i 1 IgE yielded correct positive classifications for 25 of 27 sesame-allergic patients with two false positives (93% PPV). Both tests were negative in 5 non-allergic patients. Patients with divergent Ses i 1 IgE and BAT results required OFC (n = 10, 24% of patients). Alternatively, sequential use of BAT, ruling in SFA followed by Ses i 1 IgE diagnosing non-allergic patients, yielded a 89% PPV, with 19% requiring OFC.

CONCLUSION

Ses i 1 IgE and BAT used together can decrease the need for OFC in most SFA patients. A prospective cohort trial is necessary to validate these results.

Basophil activation test in food allergy: is it ready for real-time?

PURPOSE OF REVIEW

Utilization of basophil activation in the diagnosis and monitoring of food allergy has gained increasing recognition. An ex-vivo functional assay, basophil activation reflects clinical reactivity, thereby providing clinically relevant insights. Moreover, as a biomarker of reactivity and tolerance, basophil activation testing (BAT) may provide a useful tool for management of food allergies. Despite its utility, significant limitations of BAT have prevented widespread use. Addressing these limitations will increase the future application and adoption of BAT in food allergy.

RECENT FINDINGS

A number of clinical trials in the past few years have demonstrated the use of BAT in the diagnosis and treatment of food allergy. Specifically, BAT has been found to be a biomarker of tolerance.

SUMMARY

Basophil activation testing is an effective biomarker for diagnosis and monitoring of food allergy.

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.

Basophil activation test: Mechanisms and considerations for use in clinical trials and clinical practice

The basophil activation test (BAT) is a functional assay that measures the degree of degranulation following stimulation with allergen or controls by flow cytometry. It correlates directly with histamine release. From the dose-response curve resulting from BAT in allergic patients, basophil reactivity (%CD63⁺ basophils) and basophil sensitivity (EC₅₀ or similar) are the main outcomes of the test. BAT takes into account all characteristics of IgE and allergen and thus can be more specific than sensitization tests in the diagnosis of allergic disease. BAT reduces the need for in vivo procedures, such as intradermal tests and allergen challenges, which can cause allergic reactions of unpredictable severity. As it closely reflects the patients' phenotype in most cases, it may be used to support the diagnosis of food, venom and drug allergies and chronic urticaria, to monitor the natural resolution of food allergies and to predict and monitor clinical the response to immunomodulatory treatments, such as allergen-specific immunotherapy and biologicals. Clinical application of BAT requires analytical validation, clinical validation, standardization of procedures and quality assurance to ensure reproducibility and reliability of results. Currently, efforts are ongoing to establish a platform that could be used by laboratories in Europe and in the USA for quality assurance and certification.

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.

Improving Diagnostic Accuracy in Food Allergy

The diagnosis of food allergy can have a major impact on the lives of patients and families, imposing dietary restrictions and limitations on social activities. On the other hand, misdiagnosis can place the patient at risk of a potentially severe allergic reaction. Therefore, an accurate diagnosis of food allergy is of utmost importance. The diagnosis of food allergy is often established by the combination of the clinical history and allergen-specific IgE; however, without a clear history of an allergic reaction, the interpretation of IgE sensitization tests can be difficult. There are also rare cases of clinical food allergy in the absence of IgE sensitization. For that reason, testing for suspected food allergy ideally requires access to oral food challenges (OFCs), which are currently the gold standard tests to diagnose food allergy. As OFCs are time consuming and involve the risk of acute allergic reactions of unpredictable severity, the question remains: how can we improve the accuracy of diagnosis before referring the patient for an OFC? Herein, we review the predictive value of different tests used to support the diagnosis of food allergy, discuss implications for therapy and prognosis, and propose a diagnostic approach to be applied in clinical practice.

Food Allergy and Intolerance: A Narrative Review on Nutritional Concerns

Adverse food reactions include immune-mediated food allergies and non-immune-mediated intolerances. However, this distinction and the involvement of different pathogenetic mechanisms are often confused. Furthermore, there is a discrepancy between the perceived vs. actual prevalence of immune-mediated food allergies and non-immune reactions to food that are extremely common. The risk of an inappropriate approach to their correct identification can lead to inappropriate diets with severe nutritional deficiencies. This narrative review provides an outline of the pathophysiologic and clinical features of immune and non-immune adverse reactions to food-along with general diagnostic and therapeutic strategies. Special emphasis is placed on specific nutritional concerns for each of these conditions from the combined point of view of gastroenterology and immunology, in an attempt to offer a useful tool to practicing physicians in discriminating these diverging disease entities and planning their correct management. We conclude that a correct diagnostic approach and dietary control of both immune- and non-immune-mediated food-induced diseases might minimize the nutritional gaps in these patients, thus helping to improve their quality of life and reduce the economic costs of their management.

Food Allergy: Catering for the Needs of the Clinician

The practice of food allergy (FA) for clinicians has boomed, with a dramatic rise in the number of patients and families seeking care and with many advances on several fronts. The practice itself sometimes is evidence-based science and sometimes an art of pattern and phenotype recognition. This article examines the tools for diagnosis and management and therapy options available to physicians providing care for patients with FA. The article touches on pressing needs of clinicians and highlights the rapid and important movements in national and international support and advances that will have a positive impact on the field of FA.

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.

Influence of Antihistamines on Basophil Activation Test in Food Allergy to Milk and Egg

Background: The basophil activation test (BAT) is used to improve the accuracy of food allergy diagnosis. To date, the influence of antiallergic drugs on BAT reactivity is poorly investigated. The aim of the study was to investigate if BAT results were influenced by antihistamine intake for 3 months in a cohort of patients with IgE-mediated food allergy to milk or egg. Methods: A retrospective, single-center, observational study was performed. We enrolled subjects with history of hypersensitivity reaction after specific food ingestion, positive skin prick tests and specific IgEs, concomitant allergic rhinitis, and, contraindication to the double-blind, placebo-controlled food challenge due to personal history of systemic reactions related to the ingestion of culprit food. Validated allergens (α-lactoalbumin, β-lactoglobulin, casein, egg white, and yolk) for BAT were used. Results: Thirty-nine patients with well-documented food symptoms and positive allergological workup were included in the study. BAT was positive in 29 patients. The mean percentages of CD63+ expression to specific culprit allergen did not change after the administration of drugs. Conclusions: This was the first study assessing the effects of oral antihistamines on basophil reactivity in cow’s milk and egg food allergy. Antihistamines do not interfere with BAT results.

Investigation of Basophil Activation Test for Diagnosing Milk and Egg Allergy in Younger Children

In children with concomitant food allergy and atopic dermatitis (AD), uncovering the causative food allergen is more arduous. We evaluated the basophil activation test (BAT) for its diagnostic value in children, including those with AD, for milk or egg allergy. We simultaneously measured serum-specific immunoglobulin E (sIgE) levels and performed BATs for cow’s milk and egg white. We compared their overall diagnostic performance using the area under the receiver operating characteristic curve (AUC) with the Delong method and compared them in children with AD. Analyses were completed for 75 children for milk allergy and for 85 children for egg allergy. The sIgE and percentage of basophils with the expression of CD63 were correlated for both milk (r = 0.384, p < 0.001) and egg (r = 0.557, p < 0.001). The AUC of sIgE (0.701) for milk allergy was significantly increased when combined with the BAT (0.805; p = 0.029). In children with AD, the AUC of the BAT (0.924) for milk allergy was significantly larger than that of sIgE (0.701; p = 0.017). The BAT is a potentially useful diagnostic tool for milk allergy in children when combined with sIgE. Moreover, it may be a surrogate marker for milk allergy in children with AD.

IgE Antibodies against Cancer: Efficacy and Safety

Immunoglobulin E (IgE) antibodies are well known for their role in allergic diseases and for contributions to antiparasitic immune responses. Properties of this antibody class that mediate powerful effector functions may be redirected for the treatment of solid tumours. This has led to the rise of a new class of therapeutic antibodies to complement the armamentarium of approved tumour targeting antibodies, which to date are all IgG class. The perceived risk of type I hypersensitivity reactions following administration of IgE has necessitated particular consideration in the development of these therapeutic agents. Here, we bring together the properties of IgE antibodies pivotal to the hypothesis for superior antitumour activity compared to IgG, observations of in vitro and in vivo efficacy and mechanisms of action, and a focus on the safety considerations for this novel class of therapeutic agent. These include in vitro studies of potential hypersensitivity, selection of and observations from appropriate in vivo animal models and possible implications of the high degree of glycosylation of IgE. We also discuss the use of ex vivo predictive and monitoring clinical tools, as well as the risk mitigation steps employed in, and the preliminary outcomes from, the first-in-human clinical trial of a candidate anticancer IgE therapeutic.

Basophils from Cancer Patients Respond to Immune Stimuli and Predict Clinical Outcome

Basophils are involved in manifestations of hypersensitivity, however, the current understanding of their propensity for activation and their prognostic value in cancer patients remains unclear. As in healthy and atopic individuals, basophil populations were identified in blood from ovarian cancer patients (n = 53) with diverse tumor histologies and treatment histories. Ex vivo basophil activation was measured by CD63 expression using the basophil activation test (BAT). Irrespective of prior treatment, basophils could be activated by stimulation with IgE- (anti-FcεRI and anti-IgE) and non-IgE (fMLP) mediated triggers. Basophil activation was detected by ex vivo exposure to paclitaxel, but not to other anti-cancer therapies, in agreement with a clinical history of systemic hypersensitivity reactions to paclitaxel. Protein and gene expression analyses support the presence of basophils (CCR3, CD123, FcεRI) and activated basophils (CD63, CD203c, tryptase) in ovarian tumors. Greater numbers of circulating basophils, cells with greater capacity for ex vivo stimulation (n = 35), and gene signatures indicating the presence of activated basophils in tumors (n = 439) were each associated with improved survival in ovarian cancer. Circulating basophils in cancer patients respond to IgE- and non-IgE-mediated signals and could help identify hypersensitivity to therapeutic agents. Activated circulating and tumor-infiltrating basophils may be potential biomarkers in oncology.

Basophil activation testing in occupational respiratory allergy to low molecular weight compounds

PURPOSE OF REVIEW

There is an unmet need for better immunological tests in cases of suspected occupational asthma to many workplace chemicals; here we consider the basophil activation test (BAT), a potential alternative to the detection of specific IgE antibodies.

RECENT FINDINGS

BAT is fairly widely used in general allergy services; and there is increasing experience of its use in the diagnosis of occupational allergy to low molecular weight agents and chemicals including wood dusts, persulphates, antibiotics and latex.

SUMMARY

There is potential for BAT to become a useful tool in the clinical consideration of occupational asthma and of its mechanisms, and even to take a place in a Bayesian-based diagnostic algorithm. Further development will only occur if specialist centres with appropriate facilities, and preferably in collaboration, contemplate its use.

Immunoglobulin E (IgE)-Mediated Food Allergy in Children: Epidemiology, Pathogenesis, Diagnosis, Prevention, and Management

A food allergy is an immunoglobulin E (IgE)-mediated hypersensitive reaction to food, which consists in the appearance of allergic symptoms; it can vary from common urticaria to even fatal anaphylaxis. The prevalence of food allergies has been increasing in the past twenty years and it represents a major public health problem in industrialized countries. The mechanism that leads to food allergies is the lack of immunologic and clinical tolerance to food allergens. The diagnosis of IgE-mediated food allergies is based on the combined use of a detailed medical history, in-vivo, and in-vitro research of specific IgE, the elimination diet, and the double-blind placebo-controlled food challenge. The only currently available treatment for allergies is the strict elimination diet. This type of attitude, which we could define as “passive”, does not overcome the risk of accidental reactions due to involuntary intake of the culprit food. For food allergy management, an “active” approach is urgently needed, such as specific allergen immunotherapy, which is currently under development and only used for research purposes. This article aims to give an updated review of IgE-mediated food allergies in pediatric populations in terms of epidemiology, pathogenesis, prevention, diagnosis, and management.

Sustained successful peanut oral immunotherapy associated with low basophil activation and peanut-specific IgE

BACKGROUND

Oral immunotherapy (OIT) can successfully desensitize many peanut-allergic subjects, but clinical tolerance diminishes over time on discontinuation, or low-dose maintenance, of peanut. Therefore, to improve the efficacy and sustainability of such therapy, we sought to identify biomarkers and clinical tools that can predict therapeutic outcomes and monitor treatment responses.

OBJECTIVE

We evaluated whether basophil activation in whole blood, and plasma levels of peanut-specific immunoglobulins, are useful biomarkers for peanut OIT.

METHODS

We longitudinally measured, before, during, and after OIT, basophil activation in whole blood ex vivo in response to peanut stimulation, and peanut-specific IgE (sIgE) and peanut-specific IgG4 (sIgG4), in a large, single-site, double-blind, randomized, placebo-controlled, phase 2 peanut OIT study. We compared basophil responsiveness and peanut-specific immunoglobulins between those who were clinically reactive and those who were tolerant to peanut oral challenges.

RESULTS

Peanut OIT significantly decreased basophil activation, peanut sIgE, Ara h 1, Ara h 2, and Ara h 3 IgE levels, and sIgE/total IgE, but increased sIgG4/sIgE. Participants who became reactive to 4 g of peanut 13 weeks off active OIT exhibited higher peanut-induced basophil activation ex vivo and higher peanut sIgE levels and sIgE/total IgE, but lower sIgG4/sIgE. Notably, participants entering the study with low basophil responsiveness were more likely to achieve treatment success. Substantial suppression of basophil activation was required to maintain long-term clinical tolerance after peanut OIT.

CONCLUSIONS

Assessments of peanut-induced basophil activation and peanut-specific immunoglobulins can help to predict treatment outcomes, and to differentiate transient desensitization versus sustained unresponsiveness after OIT.

Microfluidic methods for precision diagnostics in food allergy

Food allergy has reached epidemic proportions and has become a significant source of healthcare burden. Oral food challenge, the gold standard for food allergy assessment, often is not performed because it places the patient at risk of developing anaphylaxis. However, conventional alternative food allergy tests lack a sufficient predictive value. Therefore, there is a critical need for better diagnostic tests that are both accurate and safe. Microfluidic methods have the potential of helping one to address such needs and to personalize the diagnostics. This article first reviews conventional diagnostic approaches used in food allergy. Second, it reviews recent efforts to develop novel biomarkers and in vitro diagnostics. Third, it summarizes the microfluidic methods developed thus far for food allergy diagnosis. The article concludes with a discussion of future opportunities for using microfluidic methods for achieving precision diagnostics in food allergy, including multiplexing the detection of multiple biomarkers, sampling of tissue-resident cytokines and immune cells, and multi-organ-on-a-chip technology.

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.

Basophils from allergic rhinitis patients show allergen-specific upregulation of thymic stromal lymphopoietin receptor

BACKGROUND

An allergic rhinitis (AR) diagnosis is based on typical nasal symptoms and allergen sensitization testing. However, it is sometimes difficult to distinguish AR from non-AR, and it is especially difficult to identify the causal allergen for immunotherapy of patients with AR.

OBJECTIVE

To identify differences among patients with AR, subjects with asymptomatic sensitization (AS), and subjects without sensitization (NS) that could facilitate the diagnosis of AR.

METHODS

We used RNA sequencing to examine differential gene expression in unstimulated and allergen-stimulated peripheral basophils from participants with NS, AS, and AR. We selected genes that were upregulated after allergen stimulation and showed differences in expression in patients with AR compared with subjects with AS and NS. Basophil surface expression of 1 gene product was examined by flow cytometry. The usefulness of gene expression in the diagnosis of AR was examined with receiver operating characteristic curves.

RESULTS

Expression of cytokine receptor-like factor 2 and its product, thymic stromal lymphopoietin receptor (TSLPR), was significantly increased in basophils of patients with AR after allergen stimulation. A significantly larger percentage of TSLPR-positive cells was observed after allergen-specific stimulation of basophils from patients with AR compared with subjects with AS. Basophil TSLPR expression was as good as or better than CD203c expression in discriminating between patients with AR and subjects with AS, as judged by receiver operating characteristic curves.

CONCLUSION

Our data suggest that TSLPR expression on basophils was specifically upregulated by allergen stimulation and might be useful for the identification of the causative allergen in patients with AR.

Basophil Activation Test: Old and New Applications in Allergy

PURPOSE OF REVIEW

The basophil activation test (BAT) using flow cytometry has supplanted traditional methods of measuring basophil degranulation using histamine and other mediator release, and can be used for clinical applications as well as to explore the immune mechanisms of effector cell response to allergen. This review discusses the advancements made in clinical, diagnostic and laboratory research of allergy utilizing an ever-evolving BAT.

RECENT FINDINGS

Being an in vitro surrogate of the allergic reaction that happens in vivo in the sick patient, the BAT can be used to support the diagnosis of various allergic conditions, such as food, drug, respiratory and insect venom allergies, and the assessment of clinical response to allergen-specific immunotherapy and other immunomodulatory treatments. The BAT can also be used for research purposes to explore the mechanisms of allergy and tolerance at the level of the basophil, for instance by manipulating IgE and IgG and their receptors and by studying intracellular signalling cascade in response to allergen. This review covers the applications of the BAT to the clinical management of allergic patients and the increased understanding of the mechanisms of immune response to allergens as well as technological advancements made in recent years.

Diagnosis of fish and shellfish allergies

Seafood allergy is a hypersensitive disorder with increasing prevalence worldwide. Effective and accurate diagnostic workup for seafood allergy is essential for clinicians and patients. Parvalbumin and tropomyosin are the most common fish and shellfish allergens, respectively. The diagnosis of seafood allergies is complicated by cross-reactivity among fish allergens and between shellfish allergens and other arthropods. Current clinical diagnosis of seafood allergy is a complex algorithm that includes clinical assessment, skin prick test, specific IgE measurement, and oral food challenges. Emerging diagnostic strategies, such as component-resolved diagnosis (CRD), which uses single allergenic components for assessment of epitope specific IgE, can provide critical information in predicting individualized sensitization patterns and risk of severe allergic reactions. Further understanding of the molecular identities and characteristics of seafood allergens can advance the development of CRD and lead to more precise diagnosis and improved clinical management of seafood allergies.

Prueba de activación de basófilos: aspectos técnicos, metodológicos y su utilidad clínica

Introducción. La prueba de activación de basófilos (PAB) se considera una técnica confiable y segura para el diagnóstico de problemas alérgicos.Objetivo. Profundizar en el estado del arte de la PAB y su utilidad clínica.Materiales y métodos. Se realizó una revisión narrativa de la literatura mediante la búsqueda electrónica en las bases de datos y metabuscadores Ovid Medline, Google Scholar y PubMed, sin limitar la búsqueda por fecha, idioma o tipo de artículo. Se buscaron artículos sobre los detalles técnicos de la PAB y su utilidad clínica en el manejo de las enfermedades alérgicas.Resultados. De los marcadores de activación, CD63 ha sido el más estudiado y es el que mejor representa un evento de degranulación anafiláctica, mientras que CD203c es representativo de varias formas de degranulación. La superioridad de uno sobre otro como prueba diagnóstica depende del problema alérgico estudiado. En cuanto a los métodos de detección de basófilos, su selección con un único marcador, CCR3, se propone como una opción con buena relación de costo-efectividad.Conclusiones. La PAB es una herramienta prometedora para evaluar en clínica las reacciones alérgicas de forma segura. Es necesario una mayor estandarización de protocolos para obtener resultados más reproducibles.

Anaphylaxis in the 21st century: phenotypes, endotypes, and biomarkers

Anaphylaxis is the most serious of all allergic reactions and can be fatal. The diagnosis is frequently delayed, and misdiagnosis often occurs with asthma or urticaria. Biomarkers such as tryptase are not routinely checked, and appropriate treatment with epinephrine is not administered in a majority of cases, increasing the risk of poor outcomes. The objective of this review is to provide a better understanding of the pathophysiology of anaphylaxis with a description of phenotypes, endotypes, and biomarkers available in both the clinical and research settings. Expanding knowledge with regard to the presentation, causes, and triggers for anaphylaxis among health care providers will improve its diagnosis and management, increase patient safety, and decrease morbidity and mortality.

Food-Induced Anaphylaxis: an Update

PURPOSE OF REVIEW

This review aims to provide an update of recent advances in the epidemiology, clinical features and diagnosis, and management of food-induced anaphylaxis (FIA).

RECENT FINDINGS

Food allergy prevalence and FIA rates continue to rise, but FIA fatalities are stable. Basophil and mast cell activation tests promise more accurate identification of food triggers. Oral, sublingual, and epicutaneous immunotherapy can desensitize a significant portion of subjects. Epinephrine use for FIA remains sub-optimal. As the burden of food allergy continues to increase, it appears that the corresponding increase in research focused on this epidemic is beginning to bear fruit. The stable number of FIA fatalities in the face of an ongoing epidemic indicates lives have already been saved. The emergence of new diagnostic tests and interventional therapies may transform the management of FIA in the coming years.

Development of a tool predicting severity of allergic reaction during peanut challenge

BACKGROUND

Reliable prognostic markers for predicting severity of allergic reactions during oral food challenges (OFCs) have not been established.

OBJECTIVE

To develop a predictive algorithm of a food challenge severity score (CSS) to identify those at higher risk for severe reactions to a standardized peanut OFC.

METHODS

Medical history and allergy test results were obtained for 120 peanut allergic participants who underwent double-blind, placebo-controlled food challenges. Reactions were assigned a CSS between 1 and 6 based on cumulative tolerated dose and a severity clinical indicator. Demographic characteristics, clinical features, peanut component IgE values, and a basophil activation marker were considered in a multistep analysis to derive a flexible decision rule to understand risk during peanut of OFC.

RESULTS

A total of 18.3% participants had a severe reaction (CSS >4). The decision rule identified the following 3 variables (in order of importance) as predictors of reaction severity: ratio of percentage of CD63^hi stimulation with peanut to percentage of CD63^hi anti-IgE (CD63 ratio), history of exercise-induced asthma, and ratio of forced expiratory volume in 1 second to forced vital capacity (FEV₁/FVC) ratio. The CD63 ratio alone was a strong predictor of CSS (P < .001).

CONCLUSION

The CSS is a novel tool that combines dose thresholds and allergic reactions to understand risks associated with peanut OFCs. Laboratory values (CD63 ratio), along with clinical variables (exercise-induced asthma and FEV₁/FVC ratio) contribute to the predictive ability of the severity of reaction to peanut OFCs. Further testing of this decision rule is needed in a larger external data source before it can be considered outside research settings.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02103270.

NUT Co Reactivity - ACquiring Knowledge for Elimination Recommendations (NUT CRACKER) study

BACKGROUND

Ambiguities exist regarding the diagnosis of tree-nut allergy, necessitating either their elimination or the performance of oral food challenges (OFCs).

OBJECTIVE

To examine the coincidences of allergies among tree-nuts and improve diagnostic testing to minimize the need for OFC.

METHODS

Eighty-three patients prospectively evaluated for walnut, pecan, cashew, pistachio, hazelnut, and almond allergy. A history of previous reactions was obtained, and standardized skin prick tests (SPTs) using finely ground tree-nut solution and basophil activation tests (BAT) were performed. Patients underwent OFC for each tree-nut they eliminated and to which a reaction in the previous 2 years was not documented.

RESULTS

While most patients were sensitized to 5-6 tree-nuts, over 50% were allergic to only 1-2 tree-nuts. The highest rate of allergy in sensitized patients was observed for walnut (74.6%) and cashew (65.6%). The rate of co-allergy for most tree-nuts was <30%. Two-thirds of walnut- and cashew-allergic patients were also allergic to pecan and pistachio, respectively, while all pecan- and pistachio-allergic patients were allergic to walnut and cashew, respectively. Receiver-operating characteristic analysis for SPT and BAT was tree-nut dependent and yielded area under the curve (AUC) values ranging from 0.75 to 0.94. Knowledge of coincident allergies in these pairs along with the combination of SPT and BAT correctly distinguished allergic from tolerant patients for walnut (87%), pecan (66%), cashew (71%), and pistachio (79%).

CONCLUSION

The data presented here should assist in differentiating between allergic and tolerant patients, decrease the need for OFC, and allow for appropriate elimination recommendations.

A comparative study on basophil activation test, histamine release assay, and passive sensitization histamine release assay in the diagnosis of peanut allergy

BACKGROUND

Allergy can be diagnosed using basophil tests. Several methods measuring basophil activation are available. This study aimed at comparing basophil activation test (BAT), histamine release assay (HR), and passive sensitization histamine release assay (passive HR) in the diagnosis of peanut allergy.

METHODS

BAT, HR, and passive HR were performed on 11 peanut-allergic and 14 nonallergic subjects. Blood was incubated with peanut extract or anti-IgE and tests were performed as follows: BAT-CD63 upregulation was assessed by flow cytometry; HR-released histamine was quantified by a glass fiber-based fluorometric method; passive HR-IgE-stripped donor basophils were incubated with participants' serum and histamine release was quantified as HR.

RESULTS

CDsens, a measure of basophil allergen sensitivity, was significantly higher for BAT (80.1±17.4) compared to HR (23.4±10.31) and passive HR (11.1±2.0). BAT, HR, and passive HR had a clinical sensitivity of 100%, 100%, and 82% and specificity of 100%, 100%, and 100%, respectively, when excluding inconclusive results. BAT identified 11 of 11 allergic patients, HR 10, and passive HR 9. Likewise, BAT recognized 12 of 14 nonallergic subjects, HR 10, and passive HR 13. However, the tests' diagnostic performances were not statistically different. Interestingly, nonreleasers in HR but not in BAT had lower basophil count compared to releasers (249 vs 630 counts/min).

CONCLUSION

BAT displayed a significantly higher CDsens compared to HR and passive HR. The basophil tests' diagnostic performances were not significantly different. Still, BAT could diagnose subjects with low basophil number in contrast to HR.

Making the Most of In Vitro Tests to Diagnose Food Allergy

Various in vitro tests assess different aspects of the underlying immune mechanism of IgE-mediated food allergy. Some can be used for diagnostic purposes; specific IgE to allergen extracts is widely available; specific IgE to allergen components is used in most specialist centers, and the basophil activation test is becoming increasingly used clinically. IgE to allergen peptides, T-cell assays, allergen-specific/total IgE ratios, and allergen-specific IgG4/IgE ratios are currently reserved for research. Different factors can modulate the likelihood of IgE-mediated food allergy of a given allergy test result, namely, the patients' age, ethnicity, previous allergic reaction to the identified food, concomitant atopic conditions, and geographical location, and need to be taken into account when interpreting the allergy test results in the clinic. The importance of the specific food, the clinical resources available, and patient preferences are additional aspects that need to be considered when deciding whether an oral food challenge is required to reach an accurate diagnosis of IgE-mediated food allergy.