Flow-based basophil activation test in immediate drug hypersensitivity. An EAACI task force position paper.

Diagnosing immediate drug hypersensitivity reactions (IDHRs) can pose a significant challenge and there is an urgent need for safe and reliable tests. Evidence has emerged that the basophil activation test (BAT), an in vitro assay that mirrors the in vivo response, can be a complementary test for many drugs. In this position paper, members of Task Force (TF) "Basophil activation test in the evaluation of Drug Hypersensitivity Reactions" from the European Academy of Allergy and Clinical Immunology (EAACI) present the data from a survey about the use and utility of BAT in IDHRs in Europe. The survey results indicate that there is a great interest for using BAT especially for diagnosing IDHRs. However, there are still main needs, mainly in the standardization of the protocols. Subsequently consensus-based recommendations were formulated for: (i) Technical aspects of BAT in IDHRs including type of sample, management of drugs, flow cytometry protocols, interpretation of the results; and (ii) Drug-specific aspects that should be taken into account when performing BAT in relation to betalactams, neuromuscular blocking agents, fluoroquinolones, chlorhexidine, opioids, radio contrast media, chemotherapeutics, biological agents, nonsteroidal anti-inflammatory drugs, COVID vaccine, and excipients. Moreover, aspects in the evaluation of pediatric population have also been considered. All this indicates that BAT offers the clinician and laboratory a complementary tool for a safe diagnostic for IDHRs, although its place in the diagnostic algorithm depends on the drug class and patient population (phenotype, geography, and age). The standardization of BAT is important for generalizing this method beyond the individual laboratory.

Hereditary angioedema (HAE) in Belgium: results from a national survey.

Background: Hereditary angioedema (HAE) is a rare heritable disorder that is characterized by recurrent, circumscribed, nonpitting, nonpruritic, often painful subepithelial swellings of sudden unpredictable onset that generally fade during 48-72 h. Epidemiological data of hereditary angioedema patients in Belgium is lacking. Methods: We set up a nation-wide, multicentric study involving the 8 Belgian hospitals known to follow-up patients with Type I and II HAE. All Belgium HAE patients were asked to fill out questionnaires that mainly covered demographic data, family history, and detailed information about diagnosis, treatment and burden of their Type I and II HAE. Results: 112 patients with type I or type II HAE could be included. Median delay between first symptoms and diagnosis was 7 years. 51% of patients had experienced pharyngeal or tongue swelling and 78% had experienced abdominal symptoms, both known to cause an important reduction in quality of life. 60% of symptomatic patients reported to receive long term prophylactic treatment. Human plasma-derived C1-esterase inhibitor concentrate was used by 56.3% of patients. 16.7% and 27.1% of patients used a 17-α-alkylated androgen and tranexamic acid as long term prophylactic therapy. Conclusions: We present the first nation-wide epidemiological study regarding HAE in Belgium. Our data show that the morbidity of HAE is not to be underestimated. Knowledge and dissemination of this data is critical in raising awareness, encouraging development of therapies and optimising nationwide management.

Clinical practice of hereditary angioedema in Belgium: opportunities for optimized care.

INTRODUCTION: Hereditary angioedema (HAE) is a rare disorder characterized by unpredictable painful and potentially life-threatening swelling episodes. The international WAO/EAACI guideline on the diagnosis and management of HAE was recently updated and provides up-to-date guidance for the management of. In this paper, we assessed to what extent the Belgian clinical practice was aligned with the revised guideline, and whether there were opportunities to optimise Belgian clinical practice in HAE. METHODS: We compared the updated international guideline for HAE with information we acquired on Belgian clinical practice, a Belgian patient registry and expert opinion analysis. The Belgian patient registry was developed with the involvement of eight Belgian reference centers for HAE patients. Eight Belgian experts, physicians in the participating centers, included patients in the patient registry and participated in the expert opinion analysis. RESULTS: The main action points to further optimise the Belgian clinical practice of HAE are Work towards total disease control and normalize patients' life by considering the use of new and innovative long-term prophylactic treatment options; (2) inform C1-INH-HAE patients about new long-term prophylactic therapies; (3) assure the availability of on-demand therapy for all C1-INH-HAE patients; (4) implement a more universally used assessment including multiple aspects of the disease (e.g. quality of life assessment) in daily clinical practice; and (5) continue and expand an existing patient registry to assure continued data availability on C1-INH-HAE in Belgium. CONCLUSIONS: In light of the updated WAO/EAACI guideline, five action points were identified and several other suggestions were made to optimise the Belgian clinical practice in C1-INH-HAE.

MRGPRX2 and Immediate Drug Hypersensitivity: Insights From Cultured Human Mast Cells.

BACKGROUND AND OBJECTIVES: Mast cell (MC) degranulation via activation of the Mas-related G protein-coupled receptor X2 (MRGPRX2) plays a key role in immediate drug hypersensitivity (IDH). However, data in humans are limited to observations in specific cell lines. Objective: To study the usefulness of silencing MRGPRX2 in human MCs with the aim of further unveiling the MRGPRX2 pathway in IDH. METHODS: MCs were cultured from CD34+ progenitor cells obtained from peripheral blood (PBCMCs) and incubated with substance P (as a positive control), rocuronium, moxifloxacin, morphine, or amoxicillin. Immunophenotyping of the cells included flow cytometry and microscopy analyses of the expression of CD117, CD203c, and MRGPRX2. Intracellular calcium was measured using Fluo-4. Degranulation was analyzed by quantifying CD63 expression. For MRGPRX2 silencing, MCs were electroporated with Dicer small interference RNAs. RESULTS: Incubation of MCs with substance P, morphine, and moxifloxacin increased intracellular calcium levels and triggered MC degranulation, which, for the drugs, is almost completely abolished by selective MRGPRX2 silencing. Despite an increase in intracellular calcium in MRGPRX2+ cells, incubation with nontoxic concentrations of rocuronium does not result in degranulation of PBCMCs. Amoxicillin has no effect on PBCMCs. CONCLUSION: The use of MRGPRX2 silencing in human MCs can provide important insights into the role of MRGPRX2 in the pathogenesis of IDH. As induction of calcium signals does not necessarily translate into a secretory response, measurement of the degranulation reaction seems more meaningful in the context of drug testing.

Consensus clinical scoring for suspected perioperative immediate hypersensitivity reactions.

BACKGROUND: Grading schemes for severity of suspected allergic reactions have been applied to the perioperative setting, but there is no scoring system that estimates the likelihood that the reaction is an immediate hypersensitivity reaction. Such a score would be useful in evaluating current and proposed tests for the diagnosis of suspected perioperative immediate hypersensitivity reactions and culprit agents. METHODS: We conducted a Delphi consensus process involving a panel of 25 international multidisciplinary experts in suspected perioperative allergy. Items were ranked according to appropriateness (on a scale of 1-9) and consensus, which informed development of a clinical scoring system. The scoring system was assessed by comparing scores generated for a series of clinical scenarios against ratings of panel members. Supplementary scores for mast cell tryptase were generated. RESULTS: Two rounds of the Delphi process achieved stopping criteria for all statements. From an initial 60 statements, 43 were rated appropriate (median score 7 or more) and met agreement criteria (disagreement index <0.5); these were used in the clinical scoring system. The rating of clinical scenarios supported the validity of the scoring system. Although there was variability in the interpretation of changes in mast cell tryptase by the panel, we were able to include supplementary scores for mast cell tryptase. CONCLUSION: We used a robust consensus development process to devise a clinical scoring system for suspected perioperative immediate hypersensitivity reactions. This will enable objectivity and uniformity in the assessment of the sensitivity of diagnostic tests.

Management of a surgical patient with a label of penicillin allergy: narrative review and consensus recommendations.

Unsubstantiated penicillin-allergy labels are common in surgical patients, and can lead to significant harm through avoidance of best first-line prophylaxis of surgical site infections and increased infection with resistant bacterial strains. Up to 98% of penicillin-allergy labels are incorrect when tested. Because of the scarcity of trained allergists in all healthcare systems, only a minority of surgical patients have the opportunity to undergo testing and de-labelling before surgery. Testing pathways can be modified and shortened in selected patients. A variety of healthcare professionals can, with appropriate training and in collaboration with allergists, provide testing for selected patients. We review how patients might be assessed, the appropriate testing strategies that can be used, and the minimum standards of safe testing.

Immediate moxifloxacin hypersensitivity: Is there more than currently meets the eye?

Immediate drug hypersensitivity reactions (IDHR) to moxifloxacin constitute a pathomechanistic conundrum and a diagnostic challenge. Our objective was to study whether simultaneous phenotyping and quantification of histamine release might add to our knowledge about the basophil activation properties of moxifloxacin and constitute a reliable diagnostic aid. Fifteen patients with an IDHR to moxifloxacin and nine moxifloxacin challenged controls were selected. All had a basophil activation test (BAT) with moxifloxacin. Flow cytometric analysis of basophil responses implied labeling for CD63, CD203c, and intracellular histamine. Unlike tolerant challenged controls, basophilic upregulation of CD203c in response to moxifloxacin was observed in seven of 15 patients. Only two of these seven patients demonstrated appearance of CD63 and release of histamine. In the remainder eight patients, no basophil responses were demonstrable. In conclusion, immediate hypersensitivity to moxifloxacin might involve mechanisms difficult to capture by traditional CD63-/CD203c-based BAT. Deciphering the complexity of quinolone IDHR seems mandatory.

Phenotypic and functional characterization of in vitro cultured human mast cells.

BACKGROUND: Mast cell progenitor cells, derived from CD34+ hematopoietic stem cells, enter the circulation and subsequently mucosal or connective tissues where they mature to mast cells. Upon activation, mast cells increase the expression of activation markers, e.g. CD63, and release histamine amongst other mediators. Traditionally, release of these mediators is quantified using assays measuring their extracellular concentration in the supernatant of stimulated cells. METHODS: Human mast cells (HuMC) were cultured from peripheral blood, phenotypically characterized, passively sensitized with allogenic IgE antibodies and finally stimulated by anti-IgE that crosslinks IgE/FcεRI complexes. Alterations in the number of cells positive for CD63 and release of histamine were quantified simultaneously by flow cytometry. RESULTS: In culture, two distinct CD45+ cell populations were identified: CD117+ CD203c+hi and CD117- CD203c+low cells. Both populations showed positivity for FcεRI, tryptase and chymase, and contained histamine. Activation resulted in a significant increase of cells positive for CD63+ up to 21% (range: 11-39) for CD117+ CD203c+hi cells (P = 0.005), and 27% (18-55) CD63+ for CD117- CD203c+low cells (P = 0.02). Baseline histamine content was higher for CD117+ CD203c+hi cells than for CD117- CD203c+low cells, respectively 994 (695-6815) Molecules of Equivalent Specific Fluorochrome V500 per cell (MESF-V500/cell) and 797 (629-4978) MESF-V500/cell (P = 0.02). After activation, CD117+ CD203c+hi cells showed significant histamine release of 578 (366-1521) MESF-V500/cell, whilst CD117- CD203c+low cells resulted in 310 (217-366) MESF-V500/cell histamine release. CONCLUSION: This study discloses that culturing HuMC from CD34+ progenitors yields 2 phenotypically distinct cell populations that display a greatly similar response upon cross-linking of IgE/FcεRI complexes. © 2016 International Clinical Cytometry Society.

Cannabis sativa allergy: looking through the fog.

IgE-mediated Cannabis (C. sativa, marihuana) allergy seems to be on the rise. Both active and passive exposure to cannabis allergens may trigger a C. sativa sensitization and/or allergy. The clinical presentation of a C. sativa allergy varies from mild to life-threatening reactions and often seems to depend on the route of exposure. In addition, sensitization to cannabis allergens can result in various cross-allergies, mostly for plant foods. This clinical entity, designated as the 'cannabis-fruit/vegetable syndrome', might also imply cross-reactivity with tobacco, natural latex and plant-food-derived alcoholic beverages. Hitherto, these cross-allergies are predominantly reported in Europe and appear mainly to rely upon cross-reactivity between nonspecific lipid transfer proteins or thaumatin-like proteins present in C. sativa and their homologues, ubiquitously distributed throughout plant kingdom. At present, diagnosis of cannabis-related allergies predominantly rests upon a thorough history completed with skin testing using native extracts from crushed buds and leaves. However, quantification of specific IgE antibodies and basophil activation tests can also be helpful to establish correct diagnosis. In the absence of a cure, treatment comprises absolute avoidance measures. Whether avoidance of further use will halt the extension of related cross-allergies remains uncertain.

Shellfish allergens: tropomyosin and beyond.

IgE-mediated shellfish allergy constitutes an important cause of food-related adverse reactions. Shellfish are classified into mollusks and crustaceans, the latter belonging to the class of arthropoda. Among crustaceans, shrimps are the most predominant cause of allergic reactions and thus more extensively studied. Several major and minor allergens have been identified and cloned. Among them, invertebrate tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calcium-binding protein, and hemocyanin are the most relevant. This review summarizes our current knowledge about these allergens.

Quantification of specific IgE antibodies in immediate drug hypersensitivity: More shortcomings than potentials?

BACKGROUND: For many physicians, quantification of serum drug-specific IgE (sIgE) antibodies constitutes the first measure in the diagnostic approach of immediate drug hypersensitivity reactions (IDHR). AIM: To review the accuracy and limitations of the main drug-sIgE tests, especially those that are commercially available. METHODS: A literature search was conducted, using the key-words allergy, diagnosis, drugs, hypersensitivity, specific IgE antibodies; this was complemented by the authors' own experience. RESULTS: The drugs that have mostly been studied appeared to be ß-lactam antibiotics, neuromuscular blocking agents (NMBA) and morphine, the latter as a biomarker for sensitisation to substituted ammonium structures that constitute the major epitope of NMBA. For ß-lactams sensitivity and specificity varied between 0-85% and 52-100%, respectively. For NMBA, sensitivity and specificity varied between 38.5-92% and 92-100%, respectively. With respect to sIgE to morphine it appears this drug to be a sensitive biomarker for sensitisation to rocuronium and suxamethonium but not for atracurium. However, sIgE morphine should not be applied in isolation to diagnose IDHR to NMBA nor opiates. CONCLUSIONS: Although drug-sIgE assay can provide valuable information they should not be performed in isolation to establish correct diagnosis, as their predictive value is not per se absolute. Larger comprehensive studies are urgently required to determine the accuracy of drug-sIgE assays.

Flow-assisted basophil activation tests in immediate drug hypersensitivity: two decades of Antwerp experience.

The last two decades have witnessed that flow-assisted analysis of in vitro-activated basophils can constitute a valuable adjunct in the in vitro diagnostic approach of immediate drug hypersensitivity reactions (IDHR). This article summarises the current experience with the basophil activation test in the diagnosis of IDHR, with particular focus on allergy to curarising neuromuscular blocking agents, antibiotics (ß-lactams and fluoroquinolones), iodinated radiocontrast media and opiates.

Flow cytometric analysis of drug-Induced basophil histamine release.

Histamine and its release can be studied by multicolor flow cytometry on a single cell level by an enzyme affinity method (HistaFlow®). However, for the time-being, the clinical and scientific application of the HistaFlow® technique remains limited. This study aims at verifying the reliability of the HistaFlow® as an instrument to quantify IgE-mediated basophil responses to drugs, i.e., rocuronium, which are believed to be less potent basophil activators than large proteinaceous allergens. Ten patients and three exposed control individuals were included in this study. Each subject underwent in vitro basophil activation tests (HistaFlow®) with 0.16 and 1.6 mmol/L rocuronium. Patients showed an activation of basophils ranging from 11 to 86% of CD63 positive basophils and a median histamine release per cell from 68 to 100% after stimulation with an optimal concentration of 1.6 mmol/L rocuronium. For the control individuals no activation was demonstrable. This study confirms that the HistaFlow® technique is a reliable tool to study histamine release by individual cells in response to drugs. Although the HistaFlow® technique will probably not add to the diagnostic management of rocuronium allergy, our findings suggest that the technique could constitute an important asset for future studies on the pathomechanism(s) of immediate drug hypersensitivity reactions. © 2015 International Clinical Cytometry Society.

The clinical utility of basophil activation testing in diagnosis and monitoring of allergic disease.

The basophil activation test (BAT) has become a pervasive test for allergic response through the development of flow cytometry, discovery of activation markers such as CD63 and unique markers identifying basophil granulocytes. Basophil activation test measures basophil response to allergen cross-linking IgE on between 150 and 2000 basophil granulocytes in <0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In addition to clinical history, skin prick test, and specific IgE determination, BAT can be a part of the diagnostic evaluation of patients with food-, insect venom-, and drug allergy and chronic urticaria. It may be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti-IgE treatment or in the natural resolution of allergy. Basophil activation test may use fewer resources and be more reproducible than challenge testing. As it is less stressful for the patient and avoids severe allergic reactions, BAT ought to precede challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. In this EAACI task force position paper, we provide an overview of the practical and technical details as well as the clinical utility of BAT in diagnosis and management of allergic diseases.