Basophil Activation Test Shows Poor Sensitivity in Immediate Amoxicillin Allergy.

BACKGROUND: In light of the pandemic of spurious penicillin allergy, correct diagnosis of amoxicillin (AX) allergy is of great importance. The diagnosis of immediate hypersensitivity reactions relies on skin tests and specific IgE, and although reliable, these are not absolutely predictive. Therefore, drug challenges are needed in some cases, which contain the risk of severe reactions. Safe in vitro diagnostics as an alternative for the drug challenge in the diagnostic workup of AX allergy would be more than welcome to fill this gap. In this respect, the basophil activation test (BAT) has shown potential, but its clinical reliability is doubtful. OBJECTIVE: To investigate the reliability of the BAT to AX and determining its exact place in the diagnostic algorithm of AX allergy. METHODS: BAT for AX was performed in 70 exposed control individuals and 66 patients diagnosed according to the European Academy of Allergy and Clinical Immunology guidelines for AX allergy. Upregulation of both CD63 and CD203c was flow-cytometrically assessed. RESULTS: Analyses revealed that 1370 µmol/L and 685 µmol/L were the most discriminative stimulation concentrations for CD63 and CD203c upregulation, respectively, and a diagnostic threshold of 9% for positivity for both markers was identified. At these concentrations, sensitivity and specificity for CD63 upregulation were 13% and 100%, respectively, and for CD203c upregulation, 23% and 98%. CONCLUSIONS: BAT with dual analysis of CD63 and CD203c is of poor performance to document AX allergy. The sensitivity is too low to let it occupy a prominent role in the diagnostic algorithm.

Recent Knowledge and Insights on the Mechanisms of Immediate Hypersensitivity and Anaphylaxis: IgE/FcεRI- and Non-IgE/FcεRI-Dependent Anaphylaxis.

Immediate hypersensitivity reactions can pose a clinical and diagnostic challenge, mainly because of the multifarious clinical presentation and distinct underlying - frequently uncertain - mechanisms. Anaphylaxis encompasses all rapidly developing and life-threatening signs and may cause death. Evidence has accumulated that immediate hypersensitivity and anaphylaxis do not necessarily involve an allergen-specific immune response with cross-linking of specific IgE (sIgE) antibodies bound to their high-affinity IgE receptor (FcεRI) on the surface of mast cells (MCs) and basophils. Immediate hypersensitivity and anaphylaxis can also result from alternative specific and nonspecific MC and basophils activation and degranulation, such as complementderived anaphylatoxins and off-target occupancy of MC and/or basophil surface receptors such as the Masrelated G protein-coupled receptor X2 (MRGPRX2). Degranulation of MCs and basophils results in the release of inflammatory mediators, which can be, depending on the underlying trigger, in a different spatiotemporal manner. In addition, hypersensitivity and anaphylaxis can occur entirely independently of MC and basophil degranulation, as observed in hypersensitivity to nonsteroidal anti-inflammatory drugs (NSAIDs) that divert normal arachidonic acid metabolism by inhibiting the cyclooxygenase (COX)-1 isoenzyme. Finally, one should remember that anaphylaxis might be part of the phenotype of particular - sometimes poorly recognizable - conditions such as clonal MC diseases (e.g. mastocytosis) and MC activation syndrome. This review provides a status update on the molecular mechanisms involved in both sIgE/FcεRI- and non-sIgE/FcεRI-dependent immediate hypersensitivity and anaphylaxis. In conclusion, there is increasing evidence for alternative pathophysiological hypersensitivity and anaphylaxis endotypes that are phenotypically and biologically indistinguishable, which are frequently difficult to diagnose, mainly because of uncertainties associated with diagnostic tests that might not enable to unveil the underlying mechanism.

Establishing diagnostic strategies for cannabis allergy.

INTRODUCTION: Cannabis is the most widely consumed illicit drug in the world and carries a risk of severe IgE-mediated allergic reactions, requiring appropriate diagnostic management. Currently available diagnostics are still relatively limited and require careful interpretation of results to avoid harmful over- and underdiagnosis. AREAS COVERED: This review focuses on the most up-to-date understandings of cannabis allergy diagnosis, starting with the main clinical features of the disease and the allergenic characteristics of Cannabis sativa, and then providing insights into in vivo, in vitro, and ex vivo diagnostic tests. EXPERT OPINION: At present, the diagnosis of IgE-mediated cannabis allergy is based on a three-step approach that starts with accurate history taking and ends with a confirmation of sensitization to the whole extract and, finally, molecular components. Although much has been discovered since its first description in 1971, the diagnosis of cannabis allergy still has many unmet needs. The lack of commercial standardized and validated extracts and in vitro assays makes a harmonized workup of cannabis allergy difficult. Furthermore, the epidemiological characteristics, and clinical implications of sensitization to different molecular components are not yet fully known. Future research will complete the picture and likely result in an individualized and standardized approach.

Flow-based allergen testing: Can mast cells beat basophils?

The basophil activation test (BAT) has emerged as a reliable complementary diagnostic to document IgE-dependent allergies and to study cross-reactivity between structural homologues. However, the BAT has some weaknesses that hinder a wider application. The BAT requires fresh blood samples and is lost as a diagnostic in patients showing a non-responder status of their cells. The BAT is difficult to standardize mainly because of the difficulty to perform batch analyses. In contrast, mast cell activation tests (MATs), using passively sensitized mast cells (MCs) with patients' sera (henceforth indicated as passive MAT; pMAT), use serum samples that can be frozen, stored, and shipped to a reference center experienced in MC lines and/or cultures and capable of offering batch testing. With the recent recognition of the Mas-related G protein-coupled receptor X2 (MRGPRX2) occupation as a putative mechanism of immediate drug hypersensitivity reactions, the MAT has another advantage compared to the BAT. MCs, in contrast to resting basophils, express the MRGPRX2 and can therefore be used to study this IgE-independent mechanism. This review provides a status update of pMAT in the diagnosis of allergic IgE-mediated hypersensitivity and speculates how direct activation of MCs via the MRGPRX2 receptor could advance paradigms for this non-allergic hypersensitivity.