Summary Specificity of sIgE was lower than previously reported; the sIgE‐to‐tIgE ratio performs better and offers excellent specificity. The sIgE‐to‐tIgE ratio can be used as an alternative diagnostic if BAT is unavailable.

Flow cytometric analysis of activated basophils, known as the basophil activation test (BAT), is a tool available for the diagnosis of IgE-mediated allergic reactions. Despite its reported clinical utility, around 10%-20% of tested subjects fall into the category of basophil non-releasers, meaning that their basophils fail to degranulate upon IgE-mediated stimulation in vitro. Several factors causing this non-releaser status have been identified, but we currently lack a unified nomenclature to define such inconclusive BAT results and the practical steps to minimize such outcomes. In accordance with the STAndards for the Reporting of Diagnostic accuracy studies (STARD) statement, non-releasers must be reported and considered in the calculation of clinical BAT performance metrics, as failure to do so significantly limits the broader implementation of BAT in routine practice. This review provides an overview of intrinsic and extrinsic factors responsible for the basophil non-releaser phenotype in BAT. Furthermore, it proposes a standardized nomenclature for consistently reporting and integrating inconclusive BAT results in the diagnostic performance metrics and suggests diagnostic algorithms to facilitate their interpretation in clinical practice.

Immediate drug hypersensitivity reactions (IDHRs) pose significant diagnostic challenges, often requiring potentially hazardous drug challenge testing (DCT). Flow cytometry-based cellular tests including the basophil activation test (BAT), the mast cell activation test (MAT) and the T cell activation test (TAT) offer promising alternatives to reduce DCT reliance. While these tests are still in development, they demonstrate potential to compete with skin tests by providing superior diagnostic performance and improved patient safety by reducing the need for DCT. Furthermore, it is encouraging that these flow cytometry-based tests are also suitable for challenging populations, such as children. Despite requiring specialised infrastructure, these tests have the potential to be cost-effective when performed in reference centres and may offer unique mechanistic insights into immediate drug hypersensitivity reactions. However, further research is needed to validate their reliability, address pharmaceutical-specific testing considerations, and potentially integrate them into clinical guidelines.

BACKGROUND:Cannabis allergy is increasingly reported, with Can s 3 as a major allergen. Investigations into sensitisation to Can s 3 utilise sophisticated techniques, including the cytometric bead assay and the basophil activation test. This study aims to utilise a fluorescence enzyme immunoassay to quantify sIgE to Can s 3, employing a recombinant Can s 3 protein. METHODS:This study included 104 cannabis allergic patients, 20 healthy controls and 70 exposed atopic controls. Specific IgE by a fluorescence enzyme immunoassay or cytometric bead assay and the basophil activation test all used the same recombinant allergen. Two-graph ROC curves were used to determine the clinically validated allergen-specific cut-off for maximal sensitivity and specificity and to facilitate direct comparison of the test performances. RESULTS:Twenty-two individuals were non-responding in the basophil activation test and were excluded from all analyses involving basophil activation test results. The clinically validated cut-off points are > 0.16 kUA/L, ≥ 0.14 kUA/L and > 5% for a fluorescence enzyme immunoassay, cytometric bead assay and basophil activation test, respectively. Utilising these thresholds, the fluorescence enzyme immunoassay exhibited a sensitivity of 72% and specificity of 74%, the cytometric bead assay demonstrated a sensitivity of 49% and specificity of 89%. In responders, the basophil activation test exhibited a sensitivity of 51% and specificity of 82%. Remarkably, low positive fluorescence enzyme immunoassay results, particularly below 0.35 kUA/L, are negative for both cytometric bead assay and basophil activation test. Conversely, utilising the conventional threshold of > 0.35 kUA/L, the sIgE a fluorescence enzyme immunoassay results exhibited greater congruence with those of the cytometric bead assay and basophil activation test. CONCLUSION:This study underscores the complexity of establishing an optimal decision threshold for the sIgE rCan s 3 fluorescence enzyme immunoassay and indicates that the clinically validated decision cut-off may not always represent the most efficacious approach.

Introduction: IgE-mediated Cannabis allergy (CA) is a potentially severe immediate hypersensitivity reaction caused by exposure to cannabis derivatives, which is frequently associated with a secondary form of plant food allergy. Areas covered: Since the first description of CA in the 1970s, the research on CA and understanding of its allergenic profile has grown. To date, five Cannabis sativa allergens have been officially registered and many others have been identified as putative. This review provides a comprehensive overview of molecular insights in the field as of 2025. Expert opinion/commentary: Many questions concerning CA remain unanswered, and the exact clinical role of certain allergens is unclear to date. Given the increasing worldwide use of cannabis, further research is needed to fill current knowledge gaps and provide accessible and effective diagnostic tools.

Les cas d’allergie au cannabis IgE-dépendante et des syndromes alimentaires associé au cannabis sont de plus en plus souvent signalés. Cependant, la prévalence exacte de l’allergie au cannabis et des syndromes de réactivité croisée associés reste inconnue et risque d’être sous-estimée en raison d’un manque de sensibilisation et d’une connaissance insuffisante du sujet parmi les professionnels de la santé. C’est pourquoi cette feuille de route pratique vise à familiariser le lecteur avec la reconnaissance précoce et la prise en charge correcte des allergies IgE-dépendantes liées au cannabis. Bien qu’il n’y ait pas encore d’allergènes moléculaires de cannabis commercialement disponibles, une approche plus personnalisée peut être obtenue en utilisant des homologues et le recombinant Can s 3 (nsLTP du cannabis), disponible en recherche. Les symptômes prédominants de l’allergie au cannabis sont la rhinite, conjonctivite et l’urticaire/angio-œdème de contact, mais des anaphylaxies sévères potentiellement mortelles sont également possibles, ainsi que des syndromes d’allergie alimentaire croisée, impliquant principalement des fruits, légumes, fruits à coque et céréales. À l’heure actuelle, la démarche diagnostique commence généralement par des prick-tests utilisant des bourgeons, des feuilles ou des graines de la plante de cannabis. La route vers une compréhension claire de l’allergie au cannabis et des allergies croisées associées est encore longue et sinueuse, mais elle mérite d’être explorée plus avant.

PURPOSE OF REVIEW:Mast cell degranulation in anaphylaxis can result from both IgE-dependent and IgE-independent mechanisms. The two conditions differ in terms of phenotype, diagnosis and specific therapeutic targets. RECENT FINDINGS:Genetic factors and IgE-sialylation might enhance IgE-dependent degranulation. MRGPRX2-dependent signal might have a synergistic effect on IgE-dependent degranulation. The data on IgG-dependent anaphylaxis highlight the significance of histamine release from mast cells. Recent advances in the field have led to the development of novel targeting treatments for both IgE-dependent and IgE-independent mast cell degranulation. SUMMARY:In-vitro analysis of human mast cells offers the possibility of studying the mechanisms underlying mast cell degranulation in anaphylaxis. The implementation of this analysis in clinical practice can advance diagnosis. Moreover, mechanistic and preclinical studies support the development of targeted treatments for IgE-dependent and IgE-independent anaphylaxis.

Editor—Immunoglobulin E (IgE) antibody-mediated allergies to opioid analgesics, such as morphine and codeine, and related antitussives, such as pholcodine, remain rare. Since 2006/2007,1 pholcodine has become increasingly infamous because of its association with anaphylaxis to neuromuscular blocking agents (NMBAs). This association, along with the publication of two incriminating case-control studies, eventually led to a recommendation to stop the sale of all pholcodine-containing medicines throughout the EU.

In the past two decades, we witnessed the evolution of the basophil activation test (BAT) from mainly research applications to a potential complementary diagnostic tool to document IgE-dependent allergies. However, BAT presents some technical weaknesses. Around 10%-15% of tested patients are non-responders, BAT can be negative immediately post-reaction and the use of fresh basophils, ideally analysed within 4 h of collection, restricts the number of tests that can be performed per sample. The need for fresh basophils is especially limiting when conducting batch analyses and interlaboratory comparisons to harmonize BAT methodology. These limitations significantly hinder the wider application of BAT and urge the development of alternative testing, such as the mast cell activation test (MAT). The essential difference between BAT and MAT is the heterogeneity of the starting material used to perform the assays. Mast cells are tissue-resident, so cannot be easily accessed. Current alternative sources for functional studies are generating primary human mast cells, differentiated from donor progenitor cells, or using immortalized mast cell lines. Hence, the methodological approaches for MAT are not only vastly different from BAT, but also different among MAT protocols. This review summarizes the advantages and disadvantages of BAT and MAT assays, dedicating special attention to elucidating the key differences between the cellular sources used and provides an overview of studies hitherto performed comparing BAT and MAT in the diagnosis of IgE-mediated food and drug allergies.

Depuis la description séminale impliquant l’occupation du récepteur X2 couplé à la protéine G liée à Mas (MRGPRX2) dans la dégranulation des mastocytes (MCs) par les médicaments, de nombreuses études ont été entreprises sur ce nouvel endotype potentiel de réactions d’hypersensibilité immédiate aux médicaments (RHMIs). Cependant, les preuves actuelles de ce mécanisme proviennent principalement de modèles animaux (mutants) ou d’études in vitro. Des preuves cliniques irréfutables chez l’homme font défaut. De plus, la traduction de ces résultats précliniques en pertinence clinique chez l’homme est difficile et doit être interprétée de manière critique. En partant de nos priorités cliniques et de notre expérience des analyses fonctionnelles des basophiles, MCs et lymphocytes T, l’objectif de cette revue est d’identifier certaines de ces difficultés, de souligner les obstacles qui pourraient entraver la transposition des observations précliniques en clinique et de mettre en évidence les différences entre les réactions médiées par les sIgE et par le MRGPRX2. Finalement, nous proposons un algorithme mécanistique théorique qui pourrait faciliter la discrimination entre la dégranulation des MCs due à l’activation de MRGPRX2 et la réticulation des anticorps IgE liés à la membrane et réactifs aux médicaments.

Up to 50% of patients with clonal mast cell disorders (cMCD) experience anaphylaxis. Phenotyping of bone marrow mast cells (BMMCs) can be helpful for elucidating the increased anaphylaxis risk. Patients with cMCDs display an elevated burden of aberrant activated BMMCs.

With increased access and decriminalization of cannabis use, cases of IgE-dependent cannabis allergy (CA) and cross-reactivity syndromes have been increasingly reported. However, the exact prevalence of cannabis allergy and associated cross-reactive food syndromes (CAFS) remains unknown and is likely to be underestimated due to a lack of awareness and insufficient knowledge of the subject among health care professionals. Therefore, this practical roadmap aims to familiarize the reader with the early recognition and correct management of IgE-dependent cannabis-related allergies. In order to understand the mechanisms underlying these cross-reactivity syndromes and to enable personalized diagnosis and management, special attention is given to the molecular diagnosis of cannabis-related allergies. The predominant signs and symptoms of CA are rhinoconjunctivitis and contact urticaria/angioedema. However, CA can also present as a life-threatening condition. In addition, many patients with CA also have distinct cross-reactivity syndromes, mainly involving fruits, vegetables, nuts and cereals. At present, five allergenic components of Cannabis sativa (Can s); Can s 2 (profilin), Can s 3 (a non-specific lipid protein), Can s 4 (oxygen-evolving enhancer protein 2 oxygen), Can s 5 (the Bet v 1 homologue) and Can s 7 (thaumatin-like protein) have been characterized and indexed in the WHO International Union of Immunological Sciences (IUIS) allergen database. However, neither of them is currently readily available for diagnosis, which generally starts by testing crude extracts of native allergens. The road to a clear understanding of CA and the associated cross-reactive food syndromes (CAFS) is still long and winding, but well worth further exploration.

Clinical & Experimental AllergyEarly View RESEARCH LETTER IgE-Mediated Mast Cell Responses to Rocuronium: A Matter of Protonation Status Didier G. Ebo, Corresponding Author Didier G. Ebo [email protected] orcid.org/0000-0003-0672-7529 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, Belgium Department of Immunology and Allergology, AZ Jan Palfijn Gent, Ghent, Belgium Correspondence: Didier G. Ebo ([email protected])Search for more papers by this authorMichel Van Houdt, Michel Van Houdt orcid.org/0000-0002-9510-6961 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorMichiel Beyens, Michiel Beyens orcid.org/0000-0002-5571-9501 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorAlessandro Toscano, Alessandro Toscano orcid.org/0000-0002-6303-8159 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorChristel Mertens, Christel Mertens orcid.org/0000-0003-2359-0771 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorAthina L. Van Gasse, Athina L. Van Gasse orcid.org/0000-0002-3434-4333 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, Belgium Faculty of Medicine and Health Sciences, Department of Paediatrics and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Paediatrics, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorPierre Bruhns, Pierre Bruhns orcid.org/0000-0002-4709-8936 Antibodies in Therapy and Pathology, Institut Pasteur, Université Paris Cité, INSERM UMR1222, Paris, FranceSearch for more papers by this authorVito Sabato, Vito Sabato orcid.org/0000-0002-1321-314X Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorJessy Elst, Jessy Elst orcid.org/0000-0003-3506-8200 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this author Didier G. Ebo, Corresponding Author Didier G. Ebo [email protected] orcid.org/0000-0003-0672-7529 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, Belgium Department of Immunology and Allergology, AZ Jan Palfijn Gent, Ghent, Belgium Correspondence: Didier G. Ebo ([email protected])Search for more papers by this authorMichel Van Houdt, Michel Van Houdt orcid.org/0000-0002-9510-6961 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorMichiel Beyens, Michiel Beyens orcid.org/0000-0002-5571-9501 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorAlessandro Toscano, Alessandro Toscano orcid.org/0000-0002-6303-8159 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorChristel Mertens, Christel Mertens orcid.org/0000-0003-2359-0771 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorAthina L. Van Gasse, Athina L. Van Gasse orcid.org/0000-0002-3434-4333 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, Belgium Faculty of Medicine and Health Sciences, Department of Paediatrics and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Paediatrics, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorPierre Bruhns, Pierre Bruhns orcid.org/0000-0002-4709-8936 Antibodies in Therapy and Pathology, Institut Pasteur, Université Paris Cité, INSERM UMR1222, Paris, FranceSearch for more papers by this authorVito Sabato, Vito Sabato orcid.org/0000-0002-1321-314X Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this authorJessy Elst, Jessy Elst orcid.org/0000-0003-3506-8200 Faculty of Medicine and Health Sciences, Department of Immunology, Allergology, Rheumatology and the Infla-Med Centre of Excellence, University of Antwerp, Antwerp, Belgium Immunology, Allergology, Rheumatology, Antwerp University Hospital, Antwerp, BelgiumSearch for more papers by this author First published: 03 July 2024 https://doi.org/10.1111/cea.14536 Funding: The authors received no specific funding for this work. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References 1D. G. Ebo, R. Bahri, C. Tontini, et al., "Mast Cell Versus Basophil Activation Test in Allergy: Current Status," Clinical and Experimental Allergy 54 (2024): 378–387. 10.1111/cea.14487 PubMedGoogle Scholar 2J. Elst, N. Moonen, M. M. van der Poorten, et al., "The Passively Sensitized Mast Cell Activation Test Is a Reliable Diagnostic for Chlorhexidine Allergy," The Journal of Allergy and Clinical Immunology. 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Cytometry Part B: Clinical Cytometry focuses on the development and applications of cellular system analysis and array based technologies as applied to clinical practice and translational research. This journal also covers relevant techniques such as flow cytometry, image cytometry, beadbased and slide-based array analyses, as well as other cell-based spectroscopic analyses. In addition, Clinical Cytometry publishes clinical and translational investigations that identify and validate the features and molecules important in diagnosis, prognosis, and therapeutic management of patients

Perioperative hypersensitivity constitutes an important health issue, with potential dramatic consequences of diagnostic mistakes. However, safe and correct diagnosis is not always straightforward, mainly because of the application of incorrect nomenclature, absence of easy accessible in-vitro/ex-vivo tests and uncertainties associated with the non-irritating skin test concentrations. In this editorial we summarize the time line, seminal findings, and major realizations of 25 years of research on the mechanisms, diagnosis, and management of perioperative hypersensitivity.