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.

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.

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.

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.

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.

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.

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.

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.

Predictive value of allergy tests for neuromuscular blocking agents: tackling an unmet need.

BACKGROUND: Neuromuscular blocking agents (NMBAs) are a predominant cause of perioperative anaphylaxis in Europe. Diagnosis of NMBA allergy relies upon the careful review of the anaesthetic report complemented with skin tests. Additional diagnostic tests are quantification of specific IgE antibodies (sIgE) and basophil activation test (BAT). However, data on the predictive value of the skin tests, the BAT and the sIgE assays (drug-specific and substituted ammonium structures) are limited or not available, mainly because such exploration requires dangerous NMBA provocation tests. METHODS: In this study, the predictive value of skin test, BAT and measurement of sIgE to substituted ammonium structures is gathered from a review of anaesthetic records of subsequent surgical procedures with NMBA administration and/or occurrence of perioperative incidents. RESULTS: We investigated a series of 272 patients with perioperative anaphylaxis, of whom 100 had undergone second general anaesthesia. Negative skin test and negative BAT assisted the selection of alternative NMBA, which were well tolerated in all cases. Five patients with a positive sIgE to rocuronium but with negative skin testing and BAT safely received rocuronium during second anaesthesia. Twelve patients with sIgE reactivity to morphine, but negative skin test and BAT to benzylisoquinolines, tolerated administration of cisatracurium or atracurium. Alternatively, benzylisoquinoline allergy went undetected in the morphine solid-phase assay. CONCLUSIONS: Skin test and BAT have an excellent negative predictive value in our series. The uneventful re-exposure of rocuronium in patients with an isolated positive sIgE result to rocuronium calls into question the predictive value of this assay and suggests sIgE serology to be less clinically predictive than the functional investigations relying upon activation of mast cells or basophils. The presence of a positive sIgE to substituted ammonium structures such as morphine does not preclude further use of benzylisoquinolines.

Allergy to illicit drugs and narcotics.

Despite their frequent use, allergy to illicit drugs and narcotics is rarely reported in literature. We present a review of the different classes of drugs of abuse that might be involved in allergies: central nervous system (CNS) depressants (such as cannabis, opioids and kava), CNS stimulants (cocaine, amphetamines, khat and ephedra) and hallucinogens such as ketamine and nutmeg. Diagnosis of drug and narcotic allergy generally relies upon careful history taking, complemented with skin testing eventually along with quantification of sIgE. However, for various reasons, correct diagnosis of most of these drug allergies is not straightforward. For example, the native plant material applied for skin testing and sIgE antibody tests might harbour irrelevant IgE-binding structures that hamper correct diagnosis. Diagnosis might also be hampered due to uncertainties associated with the non-specific histamine releasing characteristics of some compounds and absence of validated sIgE tests. Whether the introduction of standardized allergen components and more functional tests, that is, basophil activation and degranulation assays, might be helpful to an improved diagnosis needs to be established. It is anticipated that due to the rare character of these allergies further validation is although necessary.

Flowcytometric diagnosis of atracurium-induced anaphylaxis.

BACKGROUND: Allergy to atracurium is a rare condition with serious consequences of diagnostic error. However, correct diagnosis is not always straightforward. The aim of this study is to assess the utility of the basophil activation test (BAT) in atracurium sensitization and to investigate its role in identifying cross-reactivity between muscle relaxants. METHODS: For validation, eight patients with perioperative anaphylaxis to atracurium and seven individuals experiencing perioperative anaphylaxis but not exposed to neuromuscular blocking agents (NMBA) were included. Furthermore, five other patient groups were included in the study, and all individuals exposed to different NMBA, either sensitized or not to the drug. Basophil activation with atracurium was analysed flow cytometrically. RESULTS: ROC analyses between eight atracurium-sensitized patients and seven nonexposed controls allowed identification of 5% as the decision threshold for BAT positivity. For this cutoff, the BAT attained a sensitivity of 63%, specificity of 100%, positive predictive value of 100% and negative predictive value of 70%. Of the atracurium-exposed individuals with a negative atracurium skin test (ST), two individuals had a clear positive BAT. BAT atracurium was positive in one cisatracurium-sensitized patient and negative in all cisatracurium-exposed patients with a negative ST to cisatracurium. All rocuronium- and suxamethonium-sensitized patients displayed a negative BAT with atracurium. CONCLUSIONS: The BAT proves to be a useful diagnostic for atracurium-induced anaphylaxis and may be complementary to STs. The technique enables quick and simultaneous testing of potentially crossreactive NMBA and the identification of safe alternatives for future surgery.

Component-resolved diagnosis of wasp (yellow jacket) venom allergy.

BACKGROUND: Wasp venom allergy is a potentially life-threatening condition with serious consequences of diagnostic error. OBJECTIVE: To assess whether component-resolved diagnosis, using non-glycosylated recombinant allergen components from yellow jacket can add to the diagnosis of wasp venom allergy. METHODS: In total, 148 patients with a wasp (yellow jacket) allergy were included, 91 with unequivocal tests, 26 with double positivity of serum-specific IgE (sIgE) to both venoms, 21 with discrepant sIgE and skin test results and finally 10 having their diagnosis only confirmed by basophil activation test (negative sIgE and skin test results). Specific IgE to recombinant species-specific allergen components Ves v 1 and Ves v 5 from yellow jacket, Api m 1 from honeybee and Ves v 5 complemented wasp venom were tested by ImmunoCAP. RESULTS: Overall, combined use of sIgE to rVes v 1 and rVes v 5 allowed correct diagnosis in 139 of the 148 patients (94%) and rApi m 1 was demonstrable in only one patient. Supplementing the traditional yellow jacket allergosorbent with rVes v 5 allowed to correctly diagnose wasp allergy in patients sensitized to Ves v 5 but demonstrating a negative sIgE to wasp venom. CONCLUSION: Component-resolved diagnoses with the wasp-specific recombinant allergen components Ves v 1 and Ves v 5 is a reliable method to diagnose yellow jacket allergy and can help to take out the sting of difficult cases. However, as the number of patients with doubt after conventional tests is small, larger collaborative studies are needed to draw more definitive conclusions. Whether the rVes v 5 supplemented yellow jacket allergosorbent constitutes an asset in the diagnostic management of wasp venom allergy remains to be further established.

New food allergies in a European non-Mediterranean region: is Cannabis sativa to blame?

BACKGROUND: Allergy to fruit and vegetables exhibit geographic variation regarding the severity of symptoms and depending on the sensitization profile of the patient. These sensitization profiles and routes remain incompletely understood. Cannabis is a very popular drug and derived from Cannabis sativa, a plant containing lipid transfer proteins (LTP) also known as important allergens in plant and fruit allergies. In this study we sought to elucidate a potential connection between C. sativa allergy and plant food allergies. METHODS: A case-control study involving 21 patients consulting for plant food allergies. Twelve patients were cannabis allergic and 9 had a pollen or latex allergy without cannabis allergy. Testing for cannabis IgE implied measurement of specific IgE, skin testing and basophil activation tests. Allergen component analysis was performed with a microarray technique. RESULTS: Plant food allergy in patients with documented cannabis allergy had more severe reactions than patients without cannabis allergy and frequently implied fruits and vegetables that are not observed in a (birch) pollen-related food syndrome. With the exception of 1 patient with cannabis allergy, all were sensitized to nonspecific (ns)-LTP. CONCLUSION: Our data suggest that illicit cannabis abuse can result in cannabis allergy with sensitization to ns-LTP. This sensitization might result in various plant-food allergies. Additional collaborative studies in different geographical areas are needed to further elucidate on this hypothesis.

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.

Age-dependent sensitization to the 7S-vicilin-like protein Cor a 11 from hazelnut (Corylus avellana) in a birch-endemic region.

BACKGROUND: Hazelnut (Corylus avellana) allergy exhibits age and geographically distinct sensitization patterns that have not yet been fully resolved. OBJECTIVE: To study sensitization to Cor a 11 in different age groups of hazelnut-allergic patients and infants with atopic dermatitis (AD) sensitized to hazelnut in a birch-endemic region. METHODS: Sera from 80 hazelnut-allergic patients, 33 infants under 1 year of age with AD (24 sensitized and 9 not sensitized to hazelnut), 32 healthy control individuals, and 29 birch pollen-allergic but hazelnut-tolerant individuals were tested for immunoglobulin (Ig) E reactivity to Cor a 11 by ImmunoCAP. IgE reactivity to Cor a 1.01, Cor a 1.04, Cor a 8, and Cor a 9 was studied by ISAC microarray. RESULTS: Forty patients (22 preschool children, 10 schoolchildren, and 8 adults) with systemic reactions on consumption of hazelnut were sensitized to Cor a 11 (respective rates of 36%, 40%, and 12.5%). Forty patients (6 preschool children, 10 schoolchildren, and 24 adults) reported oral allergy syndrome but only 2 of them (of preschool age) were sensitized to Cor a 11. Two (8%) of the AD infants sensitized to hazelnut showed IgE reactivity to Cor a 11. This reactivity was not observed in any of the AD infants without sensitization to hazelnut, in any of the birch-pollen allergic patients without hazelnut allergy, or in any of the healthy control individuals. CONCLUSION: Sensitization to Cor a 11 in a birch-endemic region is predominantly found in children with severe hazelnut allergy, a finding that is consistent with observations concerning sensitization to Cor a 9.

Allergy to chlorhexidine: beware of the central venous catheter.

The example reported here illustrates the frequent belief that "innocent" products such as central venous catheters do not produce allergic reactions. However, they might be impregnated with chlorhexidine and elicit serious life-threatening anaphylaxis in patients with allergy to this antiseptic agent.