EAACI guidelines on the diagnosis of IgE-mediated food allergy.

This European Academy of Allergy and Clinical Immunology guideline provides recommendations for diagnosing IgE-mediated food allergy and was developed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Food allergy diagnosis starts with an allergy-focused clinical history followed by tests to determine IgE sensitization, such as serum allergen-specific IgE (sIgE) and skin prick test (SPT), and the basophil activation test (BAT), if available. Evidence for IgE sensitization should be sought for any suspected foods. The diagnosis of allergy to some foods, such as peanut and cashew nut, is well supported by SPT and serum sIgE, whereas there are less data and the performance of these tests is poorer for other foods, such as wheat and soya. The measurement of sIgE to allergen components such as Ara h 2 from peanut, Cor a 14 from hazelnut and Ana o 3 from cashew can be useful to further support the diagnosis, especially in pollen-sensitized individuals. BAT to peanut and sesame can be used additionally. The reference standard for food allergy diagnosis is the oral food challenge (OFC). OFC should be performed in equivocal cases. For practical reasons, open challenges are suitable in most cases. Reassessment of food allergic children with allergy tests and/or OFCs periodically over time will enable reintroduction of food into the diet in the case of spontaneous acquisition of oral tolerance.

Elevated, FcεRI-dependent MRGPRX2 expression on basophils in chronic urticaria.

Background: Chronic urticaria (CU) is a skin condition driven by mast cells and basophils. The exact responsiveness profile of these cells, especially regarding the anti-IgE treatment, Omalizumab, is not fully investigated. We sought to characterize the surface activation profile of basophils in CU during Omalizumab treatment and their responsiveness to IgE and non-IgE stimulation. Methods: Whole blood basophils from 11 CU patients and 10 healthy controls were stimulated with either medium, anti-IgE, fMLP, C5a, or Substance P for 30 min and characterized by flow cytometry. Results: CU patients showed a broad range of basophil count as opposed to healthy subjects. An increased number of unstimulated CD69+ (p = 0.05), but not CD63+ basophils was observed in CU groups in comparison to healthy. The expression of CD203c and CD200R were comparable between all groups, whilst the FcεRI was reduced with the treatment. Both IgE and non-IgE mediated stimulations upregulated CD63, CD203c and CD200R, but not CD69 in all groups, however, no difference between the groups was observed. Among unstimulated basophils, expression of MRGPRX2 was higher in CU patients after Omalizumab treatment than in the healthy group (2.4% vs. 1.5%, p = 0.01). The anti-IgE stimulation increased the number of MRGPRX2-expressing basophils in the CU group before and after omalizumab as compared to the healthy (p = 0.003; p = 0.005). The fMLP and C5a stimulations showed a similar effect to the IgE-mediated stimulation. The MRGPRX2 ligand, Substance P did not activate basophils. Conclusion: CU basophils show increased expression of MRGPRX2 after IgE and non-IgE stimulation.

Delabeling of Penicillin Allergy: Room for Improvement.

BACKGROUND: Penicillin allergy labels have been shown to be associated with suboptimal treatment, negative health outcomes, and increased antibiotic resistance. Many inpatients claim to have penicillin allergy, but studies show that allergy can be disproved and the label removed in up to 90% of cases. OBJECTIVES: The purpose of the study was to investigate the proportion of patients with a penicillin allergy label in a Danish hospital and to classify patients according to the risk of having penicillin allergy in "no risk," low, and high risk. METHODS: For 22 days, inpatients with penicillin allergy labels were interviewed, had their dispensed penicillin prescriptions examined, and were subsequently categorized into risk groups based on the risk evaluation criteria in national guidelines. RESULTS: In total, 260 patients had a penicillin allergy label (10% of the inpatients). Out of 151 included patients, 25 were "no risk" patients (17%), who could potentially have their penicillin allergy label removed without testing. 42 were low-risk patients (28%). 10 "no risk" patients and 20 low-risk patients had been prescribed and dispensed one or more penicillins despite an allergy label. CONCLUSION: Ten percent of inpatients have a penicillin allergy label in a Danish hospital. 17% of these could potentially have their penicillin allergy label removed without allergy testing.

Expression of CCR8 and CCX-CKR on Basophils in Chronic Urticaria Is Amplified by IgE-Mediated Activation.

Recruitment to the local tissue and alerted phenotype are the hallmarks of basophils in chronic urticaria (CU). Chemokine receptors such as chemokine (C-C motif) receptor 4 (CCR4) or CCR8 have been studied in skin diseases, e.g., atopic dermatitis, but not in CU. In this study, we aimed to define CU's basophil homing potential and receptor profile and the effect of Omalizumab treatment on these. Unstimulated and activated (anti-IgE, fMLP, C5a, and Substance P) whole blood basophils from 11 Omalizumab-treated CU patients and 10 healthy subjects were investigated with flow cytometry. Unstimulated basophils in CU showed higher expression of the skin-associated (CCR8) and scavenger (CCX-CKR) receptors and lower expression of the lung-associated (CCR3) receptor in contrast to healthy ones. IgE-mediated activation increased the percentage of CCR8 and CCX-CKR in CU compared to healthy group and elevated the expression of the lung-associated chemokine receptor, XCR1, in all groups. A trend of augmented expression of the coagulation cascade (CD87) and fMLP (FPR1) receptors was seen on basophils in CU, while a tendency of reduced expression was seen for itch (IL-31RA) and immunotolerance (CD109) receptors. fMLP and C5a increased the expression of CCR4, CCR8, CCX-CKR, and CD87 and decreased CCR2 and CCR3, though no changes between the groups were found. In conclusion, CU basophils exhibit skin-homing potential amplified by IgE-mediated stimulation.

Managing food allergy: GA2LEN guideline 2022.

Food allergy affects approximately 2-4% of children and adults. This guideline provides recommendations for managing food allergy from the Global Allergy and Asthma European Network (GA2LEN). A multidisciplinary international Task Force developed the guideline using the Appraisal of Guidelines for Research and Evaluation (AGREE) II framework and the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. We reviewed the latest available evidence as of April 2021 (161 studies) and created recommendations by balancing benefits, harms, feasibility, and patient and clinician experiences. We suggest that people diagnosed with food allergy avoid triggering allergens (low certainty evidence). We suggest that infants with cow's milk allergy who need a breastmilk alternative use either hypoallergenic extensively hydrolyzed cow's milk formula or an amino acid-based formula (moderate certainty). For selected children with peanut allergy, we recommend oral immunotherapy (high certainty), though epicutaneous immunotherapy might be considered depending on individual preferences and availability (moderate certainty). We suggest considering oral immunotherapy for children with persistent severe hen's egg or cow's milk allergy (moderate certainty). There are significant gaps in evidence about safety and effectiveness of the various strategies. Research is needed to determine the best approaches to education, how to predict the risk of severe reactions, whether immunotherapy is cost-effective and whether biological therapies are effective alone or combined with allergen immunotherapy.

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.

The Allergen-Specific IgE Concentration Is Important for Optimal Histamine Release From Passively Sensitized Basophils.

Background: The basophil histamine release (HR) assay can be used for allergy diagnosis in addition to the conventional measurement of allergen-specific IgE (sIgE). Passive sensitization of basophils increases the versatility and allows testing the biological relevance of allergen-induced IgE cross-linking in any serum unbiased by the cellular component. However, not all the patient sera perform equally well and we hypothesized that the absolute level and fraction of sIgE affect the performance. Choosing birch pollen allergy as a model, we investigated the concentration of sIgE needed for successful passive sensitization using soluble- or matrix-fixed Bet v 1. Methods: Twenty-eight sera with Bet v 1 sIgE [7 sera within each allergy class (1: 0.1-0.70 kUA/L, 2: 0.71-3.50 kUA/L, 3: 3.51-17.50 kUA/L, and 4+: >17.50 kUA/L)] and a negative control serum pool were used to passively sensitize donor basophils, obtained from buffy coat blood (n = 3). The cells were incubated (30 min) with a soluble allergen (rBet v 1 from 0.2 to 50 ng/ml), matrix-fixed allergen (ImmunoCAP™ containing recombinant Bet v 1), or phorbol 12-myristate 13-acetate (PMA)/ionomycin mixture (maximal HR) and released histamine was quantified fluorometrically. Results: The lowest level of Bet v 1 sIgE generating a detectable HR (HR > 10% of maximal release) in all the 3 runs was found to be 1.25 kUA/L (corresponding to allergy class 2, 0.71-3.50 kUA/L). Furthermore, sera from allergy classes 3 and 4+ ascertained a significant reproducible HR: 42/42 vs. 5/21 in allergy class 1 and 15/21 in allergy class 2. Using ImmunoCAP™s containing Bet v 1 as a matrix-fixed allergen system, similar results were obtained where the lowest sIgE concentration mediating an HR was 1.68 kUA/L and 7/7 for both allergy classes 3 and 4+. Conclusion: The results demonstrate that the IgE titer is strikingly robust in predicting the ability to sensitize basophils and produce a measurable HR.

Characterization of Mast Cells from Healthy and Varicose Human Saphenous Vein.

Mast cells (MCs) are distributed in tissues throughout the body and are highly involved in many physiological and pathophysiological processes. The potential and involvement of different MC phenotypes are still not well understood. MCs are present in blood vessel walls, but their specific phenotypic features are unknown. We aimed at characterizing MCs from human saphenous veins for localization, mediator content, and receptor expression. This was done in MCs from both healthy and varicose human saphenous veins (hSV and vSV, respectively). For both vSV and hSV, we found that vein MCs are mainly present in the tunica adventitia (99% MCs in adventitia) and that the population consists of both MCT and MCTC phenotypes (vSV: 55% MCT, hSV: 64% MCT). The vein MCs contained high levels of histamine (vSV: 27 pg/MC, hSV: 55 pg/MC) and tryptase (vSV: 98 pg/MC, hSV: 111 pg/MC), indicating a strong potential for regulatory effects on blood vessels. The receptor expression of FcεRI, MRGPRX2, PTAFR, C3aR, and C5aR was found, even though the percentage of positive cells differed between vSV and hSV MCs. We conclude that vein MCs from the blood vessel wall have a high potential to affect the tissue around them.

Safe De-Labeling of Patients at Low Risk of Penicillin Allergy in Denmark.

INTRODUCTION: Penicillin allergy is suspected in 10% of hospital inpatients but can be disproved in 90% of cases. Direct oral provocation without preceding tests among low-risk patients has proven to be safe in studies of both children and adults and is gaining use across the world. The aims of this study were to investigate the rate of severe allergic reactions to direct oral drug provocation, without preceding tests, in penicillin allergy patients stratified to be at low risk, as well as to examine if these patients have barriers to penicillin allergy de-labeling and future use of penicillins. METHODS: Adult patients referred to a university hospital allergy clinic with a suspected penicillin allergy were prospectively risk evaluated. Patients stratified to be at low risk were offered a direct oral provocation with a single-dose amoxicillin followed by 4 days of continued treatment. The same risk stratification criteria were applied to a larger retrospective cohort. RESULTS: In the prospective study population, 202 patients had a direct oral drug provocation and 20 (10%) were positive. There were no cases of anaphylaxis or severe delayed hypersensitivity. Fifteen reactions were benign rashes with onset >1 day after initial dosing, and 13 of these were maculopapular rashes. The same low-risk criteria were applied retrospectively to patients in a drug provocation database, and 1,759 patients fulfilled the criteria; of these, 10% had positive provocations, and there were no cases of anaphylaxis or severe delayed hypersensitivity. De-labeled patients in the prospective study reported not to fear future penicillin intake, after prolonged provocation. CONCLUSION: The risk stratification criteria for identifying low-risk patients for the oral drug provocation test without prior skin testing were safe in terms of avoiding anaphylaxis or severe delayed hypersensitivity. Benign delayed skin reactions still occurred, and access to allergy advice and follow-up is necessary.

Development and validation of the food allergy severity score.

BACKGROUND: The heterogeneity and lack of validation of existing severity scores for food allergic reactions limit standardization of case management and research advances. We aimed to develop and validate a severity score for food allergic reactions. METHODS: Following a multidisciplinary experts consensus, it was decided to develop a food allergy severity score (FASS) with ordinal (oFASS) and numerical (nFASS) formats. oFASS with 3 and 5 grades were generated through expert consensus, and nFASS by mathematical modeling. Evaluation was performed in the EuroPrevall outpatient clinic cohort (8232 food reactions) by logistic regression with request of emergency care and medications used as outcomes. Discrimination, classification, and calibration were calculated. Bootstrapping internal validation was followed by external validation (logistic regression) in 5 cohorts (3622 food reactions). Correlation of nFASS with the severity classification done by expert allergy clinicians by Best-Worst Scaling of 32 food reactions was calculated. RESULTS: oFASS and nFASS map consistently, with nFASS having greater granularity. With the outcomes emergency care, adrenaline and critical medical treatment, oFASS and nFASS had a good discrimination (receiver operating characteristic area under the curve [ROC-AUC]>0.80), classification (sensitivity 0.87-0.92, specificity 0.73-0.78), and calibration. Bootstrapping over ROC-AUC showed negligible biases (1.0 × 10-6 -1.23 × 10-3 ). In external validation, nFASS performed best with higher ROC-AUC. nFASS was strongly correlated (R 0.89) to best-worst scoring of 334 expert clinicians. CONCLUSION: FASS is a validated and reliable method to measure severity of food allergic reactions. The ordinal and numerical versions that map onto each other are suitable for use by different stakeholders in different settings.

Optimizing investigation of suspected allergy to polyethylene glycols.

BACKGROUND: Polyethylene glycols (PEGs) are polymers of varying molecular weight (MW) used widely as excipients in drugs and other products, including the mRNA vaccines against coronavirus disease 2019. Allergy to PEGs is rare. Skin testing and graded challenge carries a high risk of inducing systemic reactions. OBJECTIVE: We evaluated skin prick test (SPT) results and in vitro reactivity over time to different MW PEGs and assessed cross-sensitization patterns in PEG allergy. METHODS: Ten patients with previously diagnosed PEG allergy underwent SPT twice with PEGs 26 months apart. Lower MW (PEG 300, 3000, 6000) were tested, followed by PEG 20,000, in stepwise, increasing concentrations. Cross-sensitization to polysorbate 80 and poloxamer 407 was assessed. SPT was performed in 16 healthy controls. In vitro basophil histamine release (HR) test and passive sensitization HR test were performed in patients and controls. RESULTS: Patients previously testing positive on SPT to PEG 3000 and/or 6000 also tested positive to PEG 20,000. Patients with a longer interval since diagnosis tested negative to lower MW PEGs and positive mainly to higher concentrations of PEG 20,000. Three patients developed systemic urticaria during SPT. Eight patients showed cross-sensitization to poloxamer 407 and 3 to polysorbate 80. All controls tested negative. In vitro tests showed limited usefulness. CONCLUSIONS: Skin test reactivity to PEG can decrease over time, but titrated SPT with increasing concentrations of PEG 20,000 can be diagnostic when lower MW PEGs test negative. To avoid systemic reactions, stepwise SPT is mandatory.

Erratum to "IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper" [World Allergy Organ J 13/2 (2020) 100080].

[This corrects the article DOI: 10.1016/j.waojou.2019.100080.].

In Vitro Investigation of Vascular Permeability in Endothelial Cells from Human Artery, Vein and Lung Microvessels at Steady-State and Anaphylactic Conditions.

Human anaphylactic reactions largely involve an increase in vascular permeability, which is mainly controlled by endothelial cells (ECs). Due to the acute and serious nature of human anaphylaxis, in vivo studies of blood vessels must be replaced or supplemented with in vitro models. Therefore, we used a macromolecular tracer assay (MMTA) to investigate the EC permeability of three phenotypes of human ECs: artery (HAECs), vein (HSVECs) and microvessels from lung (HMLECs). ECs were stimulated with two fast-acting anaphylactic mediators (histamine and platelet-activating factor (PAF)) and one longer-lasting mediator (thrombin). At steady-state conditions, HSVEC monolayers were the most permeable and HMLEC the least (15.8% and 8.3% after 60 min, respectively). No response was found in ECs from artery or vein to any stimuli. ECs from microvessels reacted to stimulation with thrombin and also demonstrated a tendency of increased permeability for PAF. There was no reaction for histamine. This was not caused by missing receptor expression, as all three EC phenotypes expressed receptors for both PAF and histamine. The scarce response to fast-acting mediators illustrates that the MMTA is not suitable for investigating EC permeability to anaphylactic mediators.