A new basophil activation test using CD63 and CCR3 in allergy to antibiotics

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.

Performance Characteristics of Basophil Activation Tests for Diagnosing Penicillin Allergy: A Meta-Analysis

BACKGROUND

Approximately 10% of the global population identify themselves as penicillin allergic, yet 90% are not truly allergic and could safely tolerate penicillin. There is no simple way to identify these people. Current in vitro diagnostics include specific immunoglobulin E (with a sensitivity of 19% and specificity of 97%) and a basophil activation test (BAT) with undefined sensitivity and specificity.

OBJECTIVE

To define the sensitivity and specificity of BAT in the diagnosis of penicillin allergy METHODS: We searched PubMed and EMBASE from inception to April 2, 2023, for original studies evaluating the performance characteristics of BAT for penicillin allergy in adults. Study selection, data extraction, risk of bias, assessment with QUADAS-2 tool, certainty assessment with Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology were performed independently, in duplicate. Meta-analysis was performed using Reitsma methodology.

RESULTS

Twenty-two studies fulfilled the inclusion criteria. Twelve used the same positive threshold giving a summary point sensitivity 51% (95% confidence interval [95% CI]46%-56%) and specificity 89% (95% CI 85%-93%). Significant risk of bias was identified owing to patient selection. GRADE certainty of evidence rated sensitivity very low due to imprecision and specificity as low. There was great heterogeneity in methods used. Use of 1,000 basophils per test did not improve performance above 500 basophils.

CONCLUSIONS

BAT sensitivity is highly variable across studies and remains too low to be considered as a routine element of clinical practice. BAT specificity is not as good as specific immunoglobulin E in penicillin allergy diagnosis. Significant further work is required in this field before clinical application of BAT in routine practice.

Tools for Etiologic Diagnosis of Drug-Induced Allergic Conditions

Drug hypersensitivity reactions are a serious concern in clinical practice because they can be severe and result in lifelong sequelae. An accurate diagnosis and identification of the culprit drug is essential to prevent future reactions as well as for the identification of safe treatment alternatives. Nonetheless, the diagnosis can be challenging. In vivo and in vitro tests can be helpful, although none are conclusive; therefore, the tests are not usually performed in isolation but as part of a diagnostic algorithm. In addition, some in vitro tests are only available in research laboratories, and standardization has not been fully accomplished. Collaborating research is needed to improve drug hypersensitivity reaction diagnosis. In this review, we update the current available in vivo and in vitro tools with their pros and cons and propose an algorithm to integrate them into clinical practice.

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.

Towards standardizing basophil identification by flow cytometry

Background

Basophils normally make up <2% of the white blood cells (WBC). There is no clear consensus for basophil identification by flow cytometry. The increased demand for basophil activation test (BAT) to identifying and monitoring allergic patients highlights the need for a standardized approach to identify basophils.

Methods

Using flow cytometry we analyzed whole blood stained with antibodies against: IgE, CD123, CD193, CD203c, CD3, HLADR, FcɛRI, CRTH2 and CD45. We examined unstimulated blood as well as blood stimulated with Anti-IgE and fMLP. Finally, we compared the results to a complete blood count (CBC) from an FDA approved hematological analyzer.

Results

Basophil identification relying on just one surface marker performed worse than approaches utilizing two identification markers. The percentage of basophils from WBC determined by flow cytometry results had a good correlation with the CBC results even though the CBC results were generally higher. Stimulating whole blood with the basophil activators did not interfere with the basophil identification markers.

Conclusion

In flow cytometry assays, two surface markers should be used for identifying basophils and if a very pure basophil fraction is desired a third marker can be considered. In our hands the approaches that included CD123 in combination with either CD193, HLADR^negative or FcɛRI performed the best.

Identification and characterization of natural PR-1 protein as major allergen from Humulus japonicus pollen

BACKGROUND

The Humulus japonicus pollen is one of the most common allergenic pollens in China. However, little is unveiled regarding the allergenic components in Humulus japonicus pollen. Our study aimed to purify and identify the pathogenesis-related 1 (PR-1) protein from Humulus japonicus pollen, and to characterize the molecular and immunochemical properties of this novel allergen.

METHODS

The natural PR-1 protein (named as Hum j PR-1) was purified from Humulus japonicus pollen extracts with a combined strategy of chromatography, and identified by mass spectrometry. The coding sequence of Hum j PR-1 was confirmed by cDNA cloning. The recombinant Hum j PR-1 was expressed and purified from Escherichia coli. The allergenicity was assessed by immunoblot, enzyme-linked immunosorbent assay (ELISA), inhibition ELISA, and basophil activation test using Humulus japonicus allergic patients' whole blood. The physicochemical properties and 3-dimensional structure of it were comprehensively characterized by in silico methods.

RESULTS

The allergenicity analysis revealed that 76.6 % (23/30) of the Humulus japonicus pollen allergic patients displayed specific IgE recognition of the natural Hum j PR-1. The cDNA sequence of Hum j PR-1 had a 516-bp open reading frame encoding 171 amino acids. Physicochemical analysis indicated that Hum j PR-1 was a stable and relatively thermostable protein. Hum j PR-1 shared a similar 3-dimensional folding pattern with other homologous allergens, which was a unique αβα sandwich structure containing 4 α-helices and 6 antiparallel β-sheets, encompassing 4 conserved CAP domain.

CONCLUSION

The natural PR-1 was firstly purified and characterized as a major allergenic allergen in Humulus japonicus pollen. These findings would contribute to developing diagnostic and therapeutic strategies for Humulus japonicus pollinosis.

A case of persistent IgE sensitisation almost two decades following ampicillin anaphylaxis

BACKGROUND

Although most immunoglobulin E (IgE)-mediated penicillin allergy wanes with time, sensitisation may occasionally persist for many years. Previous reports on the loss of penicillin-specific IgE sensitisation were based on non-anaphylaxis cases and, although uncommon, persistent sensitisation may still be possible in the minority of cases.

OBJECTIVE

This case highlights that irrespective of the elapsed duration since the index reaction, it is important to remain vigilant when approaching patients with a history of severe reactions.

MATERIAL AND METHODS

We described a case of persistent IgE sensitisation almost two decades following ampicillin anaphylaxis.

RESULTS

A 78-year-old male with a history of perioperative penicillin anaphylaxis in 2003 was referred for allergy workup in 2022 before his knee joint replacement surgery. The patient had strictly avoided all beta-lactams since the index reaction. However, his penicillin-specific sensitisation persisted, evidenced by positive skin tests (with generalised urticaria after intradermal testing) and basophil activation tests.

CONCLUSION

To our knowledge, this was the first case of positive BAT tested around two decades following the index reaction. This case illustrates that a cautious approach may still be warranted in patients with a history of severe reaction to penicillin regardless of the duration since the reported index reaction.

Basophil Activation to Gluten and Non-Gluten Proteins in Wheat-Dependent Exercise-Induced Anaphylaxis

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a cofactor-induced wheat allergy. Gluten proteins, especially ω5-gliadins, are known as major allergens, but partially hydrolyzed wheat proteins (HWPs) also play a role. Our study investigated the link between the molecular composition of gluten or HWP and allergenicity. Saline extracts of gluten (G), gluten with reduced content of ω5-gliadins (G-ω5), slightly treated HWPs (sHWPs), and extensively treated HWPs (eHWPs) were prepared as allergen test solutions and their allergenicity assessed using the skin prick test and basophil activation test (BAT) on twelve patients with WDEIA and ten controls. Complementary sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE), high-performance liquid chromatography (HPLC), and mass spectrometry (MS) analyses revealed that non-gluten proteins, mainly α-amylase/trypsin inhibitors (ATIs), were predominant in the allergen test solutions of G, G-ω5, and sHWPs. Only eHWPs contained gliadins and glutenins as major fraction. All allergen test solutions induced significantly higher %CD63⁺ basophils/anti-FcεRI ratios in patients compared with controls. BAT using sHWPs yielded 100% sensitivity and 83% specificity at optimal cut-off and may be useful as another tool in WDEIA diagnosis. Our findings indicate that non-gluten proteins carrying yet unidentified allergenic epitopes appear to be relevant in WDEIA. Further research is needed to clarify the role of nutritional ATIs in WDEIA and identify specific mechanisms of immune activation.

Innovative robust basophil activation test using a novel gating strategy reliably diagnosing allergy with full automation

BACKGROUND

Allergy is one of the most common chronic diseases in Europe. Therefore, an increased need for specific and sensitive diagnostic tests that truly detect allergy exists. This study aimed at establishing a highly specific high-throughput and automated basophil activation test (BAT) that proves the existence of an allergy with utmost probability.

METHODS

BAT from 1104 samples was analyzed; a novel gating strategy with three antibodies (FcεRIα, CD203c, CD63) was established and compared with our published protocol (12 antibodies). Based on the novel gating strategy, storage conditions, automated measurement, and analyses using R (1376 samples out of 1389) were optimized to set up a high-throughput BAT.

RESULTS

No differences in sensitivity and specificity were found between the novel three antibody (FcεRIα, CD203c, CD63) and the 12 antibody gating strategy or between automated and manually analyzed samples (saving up to 90% of labor time). The time frame for basophil activation measurement after blood donation has been extended considerably (whole blood storage ≤7 days (RT) and 17 days (4°C) prior to BAT preparation and measurement). Respective storage conditions were optimized for samples after stimulation, staining, and preparation (≤7 days (RT) and 28 days (4°C)). These achievements were confirmed by a nationwide ring trial showing robustness and applicability of our BAT on a variety of flow cytometers.

CONCLUSION

Our considerable optimizations overcame the hurdles that until now prevented the BAT from being used as high-throughput allergy diagnostic test in routine laboratories and shall allow for collaborative studies between clinics and research centers.

Practical guidelines for the response to perioperative anaphylaxis

Perioperative anaphylaxis is a severe adverse event during anesthesia that requires prompt diagnosis and treatment by physicians, including anesthesiologists. Muscle relaxants and antibiotics are the most common drugs that cause perioperative anaphylaxis in Japan, as in many countries. In addition, sugammadex appears to be a primary causative agent. Obtaining previous anesthesia records is necessary in a patient with a history of allergic reactions during anesthesia, whenever possible, to avoid recurrence of anaphylaxis. Although medical staff are likely to notice abnormal vital signs because of complete monitoring during anesthesia, surgical drapes make it difficult to notice the appearance of skin symptoms. Even if there are no skin symptoms, anaphylaxis should be suspected, especially when hypotension resistant to inotropes and vasopressors persists. For improving the diagnostic accuracy of anaphylaxis, it is helpful to collect blood samples to measure histamine/tryptase concentrations immediately after the events and at baseline. The first-line treatment for anaphylaxis is adrenaline. In the perioperative setting, adrenaline should be administered through the intravenous route, which has a faster effect onset and is secured in most cases. Adrenaline can cause serious complications including severe arrhythmias if the appropriate dose is not selected according to the severity of symptoms. The anesthesiologist should identify the causative agent after adverse events. The gold standard for identifying the causative agent is the skin test, but in vitro tests including specific IgE antibody measurements and basophil activation tests are also beneficial. The Working Group of the Japanese Society of Anesthesiologists has developed this practical guide to help appropriate prevention, early diagnosis and treatment, and postoperative diagnosis of anaphylaxis during anesthesia.Grade of recommendations and levels of evidence Anaphylaxis is a relatively rare condition with few controlled trials, and thus a so-called evidence-based scrutiny is difficult. Therefore, rather than showing evidence levels and indicating the level of recommendation, this practical guideline only describes the results of research available to date. The JSA will continue to investigate anaphylaxis during anesthesia, and the results may lead to an amendment of this practical guideline.

The basophil activation test differentiates between patients with wheat-dependent exercise-induced anaphylaxis and control subjects using gluten and isolated gluten protein types

BACKGROUND

Oral food challenge using gluten and cofactors is the gold standard to diagnose wheat-dependent exercise-induced anaphylaxis (WDEIA), but this procedure puts patients at risk of an anaphylactic reaction. Specific IgE to ω5-gliadins as major allergens and skin prick tests to wheat may yield negative results. Thus, we designed a proof-of-principle study to investigate the utility of the basophil activation test (BAT) for WDEIA diagnosis.

METHODS

Different gluten protein types (GPT; α-, γ-, ω1,2- and ω5-gliadins, high-molecular-weight glutenin subunits [HMW-GS] and low-molecular-weight glutenin subunits [LMW-GS]) and gluten were used in different concentrations to measure basophil activation in 12 challenge-confirmed WDEIA patients and 10 control subjects. The results were compared to routine allergy diagnostics. Parameters analyzed include the percentage of CD63+ basophils, the ratio of %CD63+ basophils induced by GPT/gluten to %CD63+ basophils induced by anti-FcεRI antibody, area under the dose-response curve and test sensitivity and specificity.

RESULTS

GPT and gluten induced strong basophil activation for %CD63+ basophils and for %CD63+/anti-FcɛRI ratio in a dose-dependent manner in patients, but not in controls (p < 0.001, respectively). BAT performance differed from acceptable (0.73 for LMW-GS) to excellent (0.91 for ω5-gliadins) depending on the specific GPT as evaluated by the area under the receiver operating characteristic curve. Patients showed individual sensitization profiles. After determination of the best cut-off points, ω5-gliadins and HMW-GS showed the best discrimination between patients and controls with a sensitivity/specificity of 100/70 and 75/100, respectively.

CONCLUSION

This study shows the alternative role of BAT in better defining WDEIA and the causative wheat allergens. The best BAT parameters to distinguish WDEIA patients from controls were %CD63+ basophil values for ω5-gliadins and HMW-GS.

Basophil activation test: Mechanisms and considerations for use in clinical trials and clinical practice

The basophil activation test (BAT) is a functional assay that measures the degree of degranulation following stimulation with allergen or controls by flow cytometry. It correlates directly with histamine release. From the dose-response curve resulting from BAT in allergic patients, basophil reactivity (%CD63⁺ basophils) and basophil sensitivity (EC₅₀ or similar) are the main outcomes of the test. BAT takes into account all characteristics of IgE and allergen and thus can be more specific than sensitization tests in the diagnosis of allergic disease. BAT reduces the need for in vivo procedures, such as intradermal tests and allergen challenges, which can cause allergic reactions of unpredictable severity. As it closely reflects the patients' phenotype in most cases, it may be used to support the diagnosis of food, venom and drug allergies and chronic urticaria, to monitor the natural resolution of food allergies and to predict and monitor clinical the response to immunomodulatory treatments, such as allergen-specific immunotherapy and biologicals. Clinical application of BAT requires analytical validation, clinical validation, standardization of procedures and quality assurance to ensure reproducibility and reliability of results. Currently, efforts are ongoing to establish a platform that could be used by laboratories in Europe and in the USA for quality assurance and certification.

Utility of Basophil Activation Test in a Case of Daisaikoto- and Yokukansan-induced Lung Injury

Drug-induced lung injury is defined as a respiratory disorder. The usefulness of the basophil activation test (BAT) for drug allergy-related cases was recently reported. The patient was an 82-year-old woman who had been taking Daisaikoto and Yokukansan (herbal medicines) 3 months before developing dry cough. She was admitted to our hospital with an initial diagnosis of pneumonia with elevated serum LDH, KL-6, and IgE. Chest CT showed bilateral ground-glass opacities. Her bronchoalveolar lavage fluid showed increased eosinophils. Finally, a BAT was positive for both medications. Based on the findings, the patient was diagnosed with Daisaikoto- and Yokukansan-induced lung injury. The current case suggests that the BAT may be useful for the diagnosis of drug-induced lung injury.

Basophil and mast cell activation tests by flow cytometry in immediate drug hypersensitivity: Diagnosis and beyond

Immediate drug hypersensitivity reactions (IDHRs) constitute a significant health issue with serious consequences of diagnostic error. The primary diagnostics to document IDHRs usually consists of quantification of drug-specific IgE (sIgE) antibodies and skin tests. Unfortunately, the positive predictive value (PPV) and negative predictive value (NPV) of these tests are not absolutely, which leaves room for new tests. Over the last two decades, the basophil activation test (BAT), in which ex vivo activation of individual basophils is quantified by flow cytometry, has emerged as a reliable complementary diagnostic to document IDHRs, to explore allergenic recognition, to study cross-reactivity and to monitor therapy. However, the BAT is technically challenging requiring specialized personnel and equipment, fresh samples and the technique is lost as a diagnostic in patients showing a non-responder status of their cells. By consequence, the BAT has still not entered mainstream application. In contrast, mast cell activation tests (MATs) use serum samples that can be frozen, stored, and shipped to a recognized reference centre experienced in mast cell (MC) lines and/or cultures and capable of offering batch testing with necessary quality controls. This review does not only highlight the use of the BAT and MAT as diagnostics in IDHRs, but also outlines the potential of both techniques in further exploring and unveiling the mechanisms that govern drug-induced basophil and MC activation and degranulation.

Cat-NPC2, a Newly Identified Allergen, With High Cross-Reactivity to Can f 7

Purpose

Pet-derived allergens are the common indoor inhalant allergens. Among them, cat and dog allergens constitute more than 80% of animal allergic patients, which greatly affect the quality-of-life of patients and increase the burden of social health care. The aim of this study was to identify Cat-Niemann pick type C2 (NPC2) protein, a homologue of Can f 7, as a new allergen.

Methods

Cat-NPC2 complementary DNA (cDNA) was cloned and optimized for amplification and expression in Escherichia coli. Then, recombinant Cat-NPC2 (rCat-NPC2) was purified by Ni²⁺ affinity chromatography. The allergenicity was assessed by enzyme-linked immunosorbent assay (ELISA), western blot and basophil activation test (BAT). Based on the sequence similarity, the cross-reactivity between Cat-NPC2 and Can f 7 was investigated by inhibition ELISA. Circular dichroism spectroscopy and homology modeling were used to characterize the structure of Cat-NPC2.

Results

The cDNA sequence of Cat-NPC2 was cloned with a 450-bp open reading frame coding for 149 amino acids (GenBank MN_737596). The condon-optimized NPC2 gene was subcloned and expressed in E. coli with a molecular weight of 18.9 kDa. The native Cat-NPC2 was detected in cat dander extracts. The allergenicity determined by ELISA, western blot and BAT suggested at least 14.5% cat-allergic patients displayed high specific immunoglobulin E (IgE) recognition of Cat-NPC2. The predicted structure of Cat-NPC2 was found to consist of 7 β-strands arranged in 2 β-sheets. An ELISA based assay showed that rCat-NPC2 bound to cholesterol in a dose dependent manner. Based on the structure and sequence similarities, IgE cross-reactivity was demonstrated between Cat-NPC2 and Can f 7/Der f 2.

Conclusions

In the study, a novel cat allergen, belonging to the NPC2 protein family, was identified and characterized at both molecular and immunological levels. The study will offer a deeper understanding of cat allergens and improve a component-resolved diagnosis in pet allergy.

Clinical value of in vitro tests for the management of severe drug hypersensitivity reactions

Drug hypersensitivity reactions (DHRs) occasionally present with severe cutaneous adverse reactions (SCARs) which result in a high risk of morbidity and mortality. Although SCARs are rare, the occurrence could lead to a significant increase in healthcare and economic burden, especially when more than one possible culprit drug is implicated. Therefore, the accurate identification of the culprit drug(s) is important for correct labeling and subsequent patient education and avoidance. To date, clinical evaluation using causality assessment has limitations because the assessment may be inaccurate due to the overlapping timelines when multiple drugs are initiated/continued. Moreover, drug provocation tests (DPTs) which is the gold standard in diagnosis, are contraindicated, and in vivo skin tests may also be associated with risks of triggering SCAR. The European Network for Drug Allergy recommended that in vitro tests, if available, should be performed before any in vivo tests. Basophil activation tests and lymphocyte transformation tests, could serve as reliable in vitro tests for both immediate and delayed-type DHR. Many academic medical centers with affiliated laboratory services offer these tests in the diagnostic evaluation of SCARs in clinical practice. This not only complements identification of the culprit drug(s), but may also be used to test for potentially non cross-reactive alternatives, hence avoiding DPTs. In this review, we summarize the roles of in vitro tests in identifying the culprit drug(s) in SCARs, issues with utilization and interpretation of test results, and our experience in clinical practice.

Basophils from Cancer Patients Respond to Immune Stimuli and Predict Clinical Outcome

Basophils are involved in manifestations of hypersensitivity, however, the current understanding of their propensity for activation and their prognostic value in cancer patients remains unclear. As in healthy and atopic individuals, basophil populations were identified in blood from ovarian cancer patients (n = 53) with diverse tumor histologies and treatment histories. Ex vivo basophil activation was measured by CD63 expression using the basophil activation test (BAT). Irrespective of prior treatment, basophils could be activated by stimulation with IgE- (anti-FcεRI and anti-IgE) and non-IgE (fMLP) mediated triggers. Basophil activation was detected by ex vivo exposure to paclitaxel, but not to other anti-cancer therapies, in agreement with a clinical history of systemic hypersensitivity reactions to paclitaxel. Protein and gene expression analyses support the presence of basophils (CCR3, CD123, FcεRI) and activated basophils (CD63, CD203c, tryptase) in ovarian tumors. Greater numbers of circulating basophils, cells with greater capacity for ex vivo stimulation (n = 35), and gene signatures indicating the presence of activated basophils in tumors (n = 439) were each associated with improved survival in ovarian cancer. Circulating basophils in cancer patients respond to IgE- and non-IgE-mediated signals and could help identify hypersensitivity to therapeutic agents. Activated circulating and tumor-infiltrating basophils may be potential biomarkers in oncology.

BAT in the Diagnosis of Drug Allergy: a Novel Tool in Clinical Daily Practice?

PURPOSE OF REVIEW

The aim of this study is to critically review the relevant literature published on basophil activation test, presenting the current knowledge and future perspectives.

RECENT FINDINGS

Basophil activation test (BAT) results varied accordingly to the class of the drug studied, and have promising results in immediate hypersensitivity reactions to pyrazolone (selective reactors), neuromuscular blockers, beta-lactams, and platinum compounds, all examples of classical IgE-mediated hypersensitivity drug reactions. Currently, BAT is applied in research settings, but based in the results of our review, the test can be considered as a diagnostic tool for daily practice for selected patients and selected drugs, when the test is available, particularly for patients who experienced severe reactions and when diagnosis cannot be stablished by serum-specific IgE and skin testing, in order to avoid unnecessary drug provocations tests.

Basophil Activation Test: Old and New Applications in Allergy

PURPOSE OF REVIEW

The basophil activation test (BAT) using flow cytometry has supplanted traditional methods of measuring basophil degranulation using histamine and other mediator release, and can be used for clinical applications as well as to explore the immune mechanisms of effector cell response to allergen. This review discusses the advancements made in clinical, diagnostic and laboratory research of allergy utilizing an ever-evolving BAT.

RECENT FINDINGS

Being an in vitro surrogate of the allergic reaction that happens in vivo in the sick patient, the BAT can be used to support the diagnosis of various allergic conditions, such as food, drug, respiratory and insect venom allergies, and the assessment of clinical response to allergen-specific immunotherapy and other immunomodulatory treatments. The BAT can also be used for research purposes to explore the mechanisms of allergy and tolerance at the level of the basophil, for instance by manipulating IgE and IgG and their receptors and by studying intracellular signalling cascade in response to allergen. This review covers the applications of the BAT to the clinical management of allergic patients and the increased understanding of the mechanisms of immune response to allergens as well as technological advancements made in recent years.

Prueba de activación de basófilos: aspectos técnicos, metodológicos y su utilidad clínica

Introducción. La prueba de activación de basófilos (PAB) se considera una técnica confiable y segura para el diagnóstico de problemas alérgicos.Objetivo. Profundizar en el estado del arte de la PAB y su utilidad clínica.Materiales y métodos. Se realizó una revisión narrativa de la literatura mediante la búsqueda electrónica en las bases de datos y metabuscadores Ovid Medline, Google Scholar y PubMed, sin limitar la búsqueda por fecha, idioma o tipo de artículo. Se buscaron artículos sobre los detalles técnicos de la PAB y su utilidad clínica en el manejo de las enfermedades alérgicas.Resultados. De los marcadores de activación, CD63 ha sido el más estudiado y es el que mejor representa un evento de degranulación anafiláctica, mientras que CD203c es representativo de varias formas de degranulación. La superioridad de uno sobre otro como prueba diagnóstica depende del problema alérgico estudiado. En cuanto a los métodos de detección de basófilos, su selección con un único marcador, CCR3, se propone como una opción con buena relación de costo-efectividad.Conclusiones. La PAB es una herramienta prometedora para evaluar en clínica las reacciones alérgicas de forma segura. Es necesario una mayor estandarización de protocolos para obtener resultados más reproducibles.

Individual risk assessment in the diagnosis of immediate type drug hypersensitivity reactions to betalactam and non-betalactam antibiotics using basophil activation test: a single center experience

BACKGROUND

Drug hypersensitivity reactions of immediate type pose a challenging problem, especially, if standard diagnostic procedures do not lead to conclusive results. The aim of this investigation is to identify, whether basophil activation test (BAT) is able to provide additional benefit in the diagnostic evaluation of immediate type drug hypersensitivity reactions to antibiotics in comparison with the routine allergological diagnostic methods.

MATERIALS AND METHODS

We investigated patients, who presented to the Department of Dermatology and Allergology of the University Hospital of RWTH Aachen in Germany for diagnostic workup of type I allergic reactions to antibiotics during the period from 2009 to 2012. The analysis was performed retrospectively based on patient records. The inclusion criteria were performed standard allergological in vivo diagnostic and a BAT as a part of diagnostic workup.

RESULTS

Eighty-two diagnostic investigations were performed in 52 patients. BAT was positive in 9 of 12 cases with a positive clinical history but negative skin test results. Furthermore, all patients who reported severe drug hypersensitivity reactions (anaphylactic reaction grade 2 and above) showed positive BAT (5/5), while only three of these five cases demonstrated a positive skin testing that led to the conclusion of possible immediate type drug hypersensitivity.

CONCLUSIONS

Although skin tests remain the most important part of the primary diagnostic investigation, BAT is an additional valuable and sensitive in vitro test in the diagnostic procedure of immediate type allergic reactions to antibiotics. However, further standardized investigations are needed in order to calculate exact sensitivity and specificity of this diagnostic tool in both, adult and pediatric populations.

Occupational generalized urticaria and anaphylaxis after inhalation of cefuroxime in a nurse

We present the case of a 53 years old nonatopic female nurse who experienced repeated anaphylactic reactions at work without involvement in drug-specific tasks such as crushing of tablets or preparation of injections. The causal allergen was not identified until a further severe anaphylactic reaction occurred after oral use of cefuroxime during a respiratory infection. Sensitization to cefuroxime was demonstrated by specific IgE, basophil activation test and skin prick test. An inhalation challenge with a dosimeter induced generalized urticaria after a cumulative dose of about 10 μg of the drug, but no asthmatic reaction. Complete exposure cessation was initiated and a 1-year follow-up was without further allergic reactions. We conclude that work-related systemic allergic reactions to β-lactam antibiotics may occur in nurses after inhalation of low doses and without perceived association with drug-specific tasks like handling of antibiotics.

In Vitro Diagnosis of Immediate Drug Hypersensitivity Anno 2017: Potentials and Limitations

Background

For most physicians, quantification of drug-specific immunoglobulin E (drug-sIgE) antibodies constitutes the primary in vitro measure to document immediate drug hypersensitivity reactions (IDHR). Unfortunately, this is often insufficient to correctly identify patients with IgE-mediated IDHR and impossible for non-IgE-mediated IDHR that result from alternative routes of basophil and mast cell activation. In these difficult cases, diagnosis might benefit from cellular tests such as basophil activation tests (BAT).

Aim

The aim was to review the potential and limitations of quantification of sIgE and BAT in diagnosing IDHR. The utility of quantification of serum tryptase is discussed.

Methods

A literature search was conducted using the key words allergy, basophil activation, CD63, CD203c, diagnosis, drugs, hypersensitivity, flow cytometry, specific IgE antibodies; this was complemented by the authors’ own experience.

Results

The drugs that have been most studied with both techniques are β-lactam antibiotics and curarizing neuromuscular blocking agents (NMBA). For sIgE morphine, data are available on the value of this test as a biomarker for sensitization to substituted ammonium structures that constitute the major epitope of NMBA, especially rocuronium and suxamethonium. For the BAT, there are also data on non-steroidal anti-inflammatory drugs (NSAIDs) and iodinated radiocontrast media. For β-lactam antibiotics, sensitivity and specificity of sIgE varies between 0 and 85% and 52 and 100%, respectively. For NMBA, sensitivity and specificity varies between 38.5 and 92% and 85.7 and 100%, respectively. Specific IgE to morphine should not be used in isolation to diagnose IDHR to NMBA nor opiates. For the BAT, sensitivity generally varies between 50 and 60%, whereas specificity attains 80%, except for quinolones and NSAIDs.

Conclusions

Although drug-sIgE assays and BAT can provide useful information in the diagnosis of IDHR, their predictive value is not absolute. Large-scale collaborative studies are mandatory to harmonize and optimize test protocols and to establish drug-specific decision thresholds.

White-fruited strawberry genotypes are not per se hypoallergenic

The strawberry fruit Fra a 1-proteins are homologues of the major birch pollen allergen Bet v 1 and have essential biological functions in pigment formation during fruit ripening. Patients affected by allergy against birch pollen tolerated fruits of a naturally occurring white-fruited F.×ananassa genotype, which showed reduced levels of Fra a 1 proteins along with enzymes of the anthocyanin pigment pathway. We evaluated the cross-reactive allergenic potential of a number of naturally occurring white- and red-fruited strawberry varieties to detect genotypes with low allergenic reactivity, whose fruit might be tolerated by patients with mild allergy. Protein extracts of 51 different strawberry varieties (Fragaria×ananassa, F. vesca, and F. nilgerensis) were screened by Western blot analysis with a polyclonal Fra a 1.02 antibody. Besides, activation of basophils of eight atopic patients allergic to birch pollen were studied using Bet v 1a and different concentrations of 15 selected strawberry protein extracts out of the 51 strawberry genotypes. Median percentages of activated basophils stimulated by extracts from white- and red-fruited genotypes ranged from 36 to 84% and 44 to 76%, respectively indicating that white-fruited strawberry are not per se hypoallergenic. Protein extracts from white-fruited F. vesca cv. Yellow Wonder showed the lowest cross-reactivity but high biological variability. The knowledge about the allergenic potential of different strawberry genotypes may help to improve food safety and can serve as starting point for the development of red-fruited hypoallergenic strawberry cultivars.

Pros and Cons of Clinical Basophil Testing (BAT)

PURPOSE OF REVIEW

We review basophil testing by flow cytometry with an emphasis on advantages and disadvantages.

RECENT FINDINGS

There are many tools available to assess the presence and severity of allergic diseases in patients. For 50 years, peripheral blood basophils have been used as tools to study these diseases. It is a very accessible cell that binds IgE antibody and secretes the classical mediators responsible for the symptoms of allergic reactions. In the last decade, an even more accessible methodology, using flow cytometry, has been developed to enhance the ability to use basophils for both mechanistic and clinical diagnostics. Basophil testing has been included in diagnostics for different forms of allergies as well as to monitor disease status. A variety of studies have begun to establish both precise methods and their clinical relevance for disease diagnosis, but there remain some important questions on how to take optimal advantage of the behaviours of basophils.

The Value of In Vitro Tests to DiminishDrug Challenges

Drug hypersensitivity reactions have multiple implications for patient safety and health system costs, thus it is important to perform an accurate diagnosis. The diagnostic procedure includes a detailed clinical history, often unreliable; followed by skin tests, sometimes with low sensitivity or unavailable; and drug provocation testing, which is not risk-free for the patient, especially in severe reactions. In vitro tests could help to identify correctly the responsible agent, thus improving the diagnosis of these reactions, helping the physician to find safe alternatives, and reducing the need to perform drug provocation testing. However, it is necessary to confirm the sensitivity, specificity, negative and positive predictive values for these in vitro tests to enable their implementation in clinical practice. In this review, we have analyzed these parameters from different studies that have used in vitro test for evaluating drug hypersensitivity reactions and estimated the added value of these tests to the in vivo diagnosis.

Utility of basophil activation testing to assess perioperative anaphylactic reactions in real-world practice

Introduction

Perioperative anaphylactic reactions due to drugs and substances associated with general anesthesia can potentially be life‐threatening. The objective of this study was to investigate the significance of the basophil activation test (BAT) for allergy diagnosis work up.

Methods

A total of 14 patients (5 men, 9 women; mean age: 57.8 years) with clinical records of anaphylactic reactions under general anesthesia were studied by means of anesthesia records, skin and serological tests. Eleven healthy subjects without any history of allergic sensitization to anaesthetic drugs served as controls. BATs based on stimulation of whole blood cells measuring CD63 activation of basophils and using CCR3 as basophil marker by flow cytometry (Flow CAST®, BÜHLMANN Laboratories AG, Schönenbuch, Switzerland) were performed with the following substances (in dependence on the history and the skin tests of the patient): analgesics (acetylsalicylic acid, celecoxib, diclofenac, ibuprofen, indometacin, metamizole, paracetamol, propyphenazone, tramadol), antibiotics (PPL (benzylpenicilloyl polylysine), MDM (minor determinant mixture), amoxicillin, cefuroxime, ciprofloxacin, doxycycline, erythromycin, roxithromycin, sulfamethoxazole, trimethoprim), local anesthetics (articaine, bupivacaine, lidocaine, prilocaine, procaine, methyl‐4‐hydroxybenzoate), narcotics and NMBA (atracurium, cisatracurium, etomidate, neostigmine, midazolam, mivacurium, pancuronium, propofol, pyridostigmine, succinylcholine, sufentanil, thiopental, vecuronium), and other individual substances.

Results

Three patients showed positive results in the BAT: One to metamizole, one to PPL, and one to pancuronium. BATs with these substances were negative in controls.

Conclusions

The BAT should be used complementary to skin tests, especially if IgE‐mediated mechanisms are presumed and skin tests are inconclusive. A positive reaction in BAT identifies the culprit agent with high probability.

Evolution of diagnostic approaches in betalactam hypersensitivity

INTRODUCTION

Betalactams are the most widely used drugs against infections and the primary cause of antibiotic hypersensitivity reactions. Reaction patterns for different betalactams have been changing in accordance with consumption trends, and vary among countries. As a consequence, in vivo and in vitro tests have had to change with to keep up with new tendencies. Areas covered: This review is focused on advances in betalactam hypersensitivity diagnosis. Changes in in vivo methods have been limited to the inclusion of new haptens. In contrast, major progress has been achieved for in vitro tests since the 1960s, from the first description of immunoassays, the basophil activation test and the lymphocyte transformation test, to the more sophisticated assays developed in last years. Expert commentary: Issues with diagnosis are related to test sensitivity. In vivo tests show higher sensitivity, however they can be risky, especially in severe and life-threatening reactions. Therefore, we believe that in vitro tests should be the preferred method. Current efforts are under way to enhance their sensitivity. Only multidisciplinary approaches involving immunology, proteomics, nanotechnology and chemistry can help us to fully understand conjugate structures and mechanisms involved in hypersensitivity reactions to betalactams, and consequently lead to advances in in vitro methods.

Adverse Medication Reactions

Cutaneous adverse drug reactions (ADRs) are among the most frequent adverse reactions in patients receiving drug therapy. They have a broad spectrum of clinical manifestations, are caused by various drugs, and result from different pathophysiological mechanisms. Hence, their diagnosis and management is challenging.

Severe cutaneous ADRs comprise a group of diseases with major morbidity and mortality, reaching 30 % mortality rate in cases of Toxic Epidermal Necrolysis.

This chapter covers the terminology, epidemiology, pathogenesis and classification of cutaneous ADR, describes the severe cutaneous ADRs and the clinical and laboratory approach to the patient with cutaneous ADR and presents the translation of laboratory-based discoveries on the genetic predisposition and pathogenesis of cutaneous ADRs to clinical management guidelines.

Basophil Reactivity as Biomarker in Immediate Drug Hypersensitivity Reactions-Potential and Limitations

Immediate drug hypersensitivity reactions (DHRs) resemble typical immunoglobulin E (IgE)-mediated symptoms. Clinical manifestations range from local skin reactions, gastrointestinal and/or respiratory symptoms to severe systemic involvement with potential fatal outcome. Depending on the substance group of the eliciting drug the correct diagnosis is a major challenge. Skin testing and in vitro diagnostics are often unreliable and not reproducible. The involvement of drug-specific IgE is questionable in many cases. The culprit substance (parent drug or metabolite) and potential cross-reacting compounds are difficult to identify, patient history and drug provocation testing often remain the only means for diagnosis. Hence, several groups proposed basophil activation test (BAT) for the diagnosis of immediate DHRs as basophils are well-known effector cells in allergic reactions. However, the usefulness of BAT in immediate DHRs is highly variable and dependent on the drug itself plus its capacity to spontaneously conjugate to serum proteins. Stimulation with pure solutions of the parent drug or metabolites thereof vs. drug-protein conjugates may influence sensitivity and specificity of the test. We thus, reviewed the available literature about the use of BAT for diagnosing immediate DHRs against drug classes such as antibiotics, radio contrast media, neuromuscular blocking agents, non-steroidal anti-inflammatory drugs, and biologicals. Influencing factors like the selection of stimulants or of the identification and activation markers, the stimulation protocol, gating strategies, and cut-off definition are addressed in this overview on BAT performance. The overall aim is to evaluate the suitability of BAT as biomarker for the diagnosis of immediate drug-induced hypersensitivity reactions.

Fra a 1.02 Is the Most Potent Isoform of the Bet v 1-like Allergen in Strawberry Fruit

The strawberry fruit proteins Fra a 1.01E-1.08 are homologues of the major birch pollen allergen Bet v 1. Three of the proteins are known to have essential biological functions in pigment formation during fruit ripening and seem to be responsible for allergic reactions to strawberry fruit. We evaluated the cross-reactive allergenic potential of these putative strawberry allergens in patients allergic to birch pollen. Activation of basophils of eight atopic patients was studied using different concentrations of Fra a 1 isoforms. Bet v 1a was used as control and as atopic patient selection criterion. Although Fra a 1.01E-1.08 have amino acid sequence identities of 74.5-97.5% with Fra a 1.02, the basophil activation mediated by the eight Fra a 1 proteins differed substantially. Fra a 1.03 and Fra a 1.02 showed the highest activation of basophils, 73 and 66% of total basophils, respectively. On the basis of the high relative expression of the gene Fra a 1.02 in ripe strawberry fruits of allergenic varieties, Fra a 1.02 was identified as the main strawberry allergen of the Bet v 1 superfamily. Knowledge of the allergenic potential of Fra a 1.02/1.03 will help to improve food safety and can serve as a valuable marker for the development of red-fruited hypoallergenic strawberry cultivars.

Randomized phase 1 study of the phosphatidylinositol 3-kinase δ inhibitor idelalisib in patients with allergic rhinitis

BACKGROUND

Phosphatidylinositol 3-kinase p110δ isoform (PI3K p110δ) activity is essential for mast cell activation, suggesting that inhibition of PI3K p110δ might be useful in treating allergic diseases.

OBJECTIVE

We sought to determine the effect of the PI3K p110δ-selective inhibitor idelalisib on allergic responses.

METHODS

This phase 1 randomized, double-blind, placebo-controlled, 2-period crossover study was conducted with the Vienna Challenge Chamber. Grass pollen-induced allergic symptoms were documented during screening. Eligible subjects received idelalisib (100 mg twice daily) or placebo for 7 days, with allergen challenge on day 7. After a 2-week washout period, subjects received the alternate treatment and repeated allergen challenge. Study measures included safety, nasal and nonnasal symptoms, nasal airflow, nasal secretions, basophil activation, and plasma cytokine levels.

RESULTS

Forty-one patients with allergic rhinitis received idelalisib/placebo (n = 21) or placebo/idelalisib (n = 20). Idelalisib treatment was well tolerated. Mean total nasal symptom scores were lower during the combined idelalisib treatment periods compared with placebo (treatment difference [idelalisib - placebo], -1.78; 95% CI, -2.53 to -1.03; P < .001). Statistically significant differences were also observed for the combined treatment periods for total symptom scores, nasal airflow, nasal secretion weight, and nasal congestion scores. The percentage of ex vivo-activated basophils (CD63(+)/CCR3(+) cells; after stimulation with grass pollen) was substantially lower for idelalisib-treated compared with placebo-treated subjects. Plasma CCL17 and CCL22 levels were reduced after idelalisib treatment.

CONCLUSION

Idelalisib treatment was well tolerated in patients with allergic rhinitis and appears to reduce allergic responses clinically and immunologically after an environmental allergen challenge.

In vitro Diagnosis of Immediate Drug Hypersensitivity: Should We Go with the Flow

BACKGROUND

Diagnosis of immediate drug hypersensitivity reactions (IDHRs) is based upon history taking, skin prick or intradermal tests and quantification of specific immunoglobulin E (IgE) antibodies. Unfortunately, this is often insufficient to correctly identify patients with IgE-mediated IDHRs and is impossible in the case of non-IgE-mediated IDHRs. Drug provocation tests (DPT) are considered the 'gold standard' diagnostic but are not always possible, for ethical and practical reasons. Therefore, the validation of new cellular tests such as basophil activation testing (BAT) was necessary. This review focuses on the applications of BAT in IDHRs.

METHODS

A literature search was conducted, using the words basophil, flow cytometry, immediate drug allergy and drugs; this was complemented by the authors' own expertise.

RESULTS

BAT/HistaFlow® is a useful diagnostic tool in IDHRs, mainly used to diagnose allergy to neuromuscular blocking agents (NMBAs), antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs) and iodinated radiocontrast media. Its sensitivity varies between 50 and 60%, and specificity attains 80%, except for with quinolones and NSAIDs.

CONCLUSIONS

The diagnostic utility of BAT (and to lesser extent HistaFlow) has been demonstrated and is mostly applied in IDHRs. However, larger-scale collaborative studies are necessary to optimize test protocols and validate the entry of BAT as a diagnostic instrument in drug allergy.

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.

Optimizing of the basophil activation test: Comparison of different basophil identification markers

BACKGROUND

Flowcytometric identification of basophils is a prerequisite for measuring activation of basophils with IgE-dependent or IgE-independent stimuli. Aim of this study was to compare different marker combinations in a simultaneous multicolor flowcytometric measurement.

METHODS

Ten patients with a grass pollen allergy and three controls were included in the study. Basophilic cells were gated by using anti-CCR3, anti-IgE, anti-CRTH2, anti-CD203c, and anti-CD3. Cells were activated by a monoclonal anti-FcεRI antibody, N-formyl-methionyl-leucyl-phenylalanine (fMLP), and the allergen extract Phleum pratense. The activation marker anti-CD63 was used.

RESULTS

The highest relative number of basophils was found with anti-CCR3+ cells, anti-IgE+ and anti-IgE+ /anti-CD203c+ cells, the lowest with CRTH2+/CD203c+/CD3- cells. A very good and good concordance of CCR3+ cells was seen with CCR3+/CD3- cells and CRTH2+/CD203c+/CD3- cells in all experiments. The contamination of the CCR3+ population with CD3+ cells and the contamination of the IgE+-population with CCR3- cells and CD203- cells were the lowest compared to all other marker combinations.

CONCLUSIONS

As the highest relative number of basophils was identified by anti-CCR3 followed by the anti-IgE and anti-IgE/antiCD203c positive population in most cases, these markers can generally be recommended for identification of basophils. If a basophil population with very high purity is needed, anti-IgE should be chosen.

Immunotherapy in allergy and cellular tests: state of art

The basophil activation test (BAT) is an in vitro assay where the activation of basophils upon exposure to various IgE-challenging molecules is measured by flow cytometry. It is a cellular test able to investigate basophil behavior during allergy and allergy immunotherapy. A panoply of critical issues and suggestive advances have rendered this assay a promising yet puzzling tool to endeavor a full comprehension of innate immunity of allergy desensitization and manage allergen or monoclonal anti-IgE therapy. In this review a brief state of art of BAT in immunotherapy is described focusing onto the analytical issue pertaining BAT performance in allergy specific therapy.

Recent applications of basophil activation tests in the diagnosis of drug hypersensitivity

Immediate-type drug hypersensitivity is an increasingly significant clinical issue; however, the diagnosis is frequently hindered due to lack of safe and precise diagnostic tests. Flow cytometry-assisted basophil activation test is a safe in vitro diagnostic tool for assessing basophil activation upon allergen stimulation. In this review, we have summarized current literature on the diagnostic utilities, new indications, and methodological aspects of the basophil activation test for the diagnosis of drug hypersensitivity.

Threshold for basophil activation test positivity in neuromuscular blocking agents hypersensitivity reactions

Background

Several different criteria for the positivity of the flow-assisted Basophil Activation Test (BAT) for the diagnosis of Neuromuscular Blocking Agents (NMBA) hypersensitivity reactions have been used in past studies. Our aims were to determine the threshold for BAT positivity expressed as the stimulation index (SI, calculated as the percentage of activated basophils after stimulation with NMBA divided by the number of basophils with no NMBA stimulation) and as the percentage of activated basophils, and to determine the sensitivity and specificity of BAT for NMBAs.

Methods

22 consenting adult patients with previous intraanaesthetic NMBAs-related hypersensitivity reactions were tested for the culprit drug. 34 controls who tolerated NMBAs were similarly tested. BAT was performed using Flow2Cast technique and the up-regulation of the CD63 marker on the basophils was measured using Cell Quest programme (FACSCalibur Becton Dickinson, USA). Receiver operating characteristics curve (ROC) analysis was performed.

Results

ROC curve analysis for BAT results versus history yields a stimulation index of 1.76 as the optimal threshold, with an AUC of 0.81 (CI 95% 0.69-0.93, p < 0.01) and a percentage of activated basophils > 5.01%, with an AUC of 0.84 (CI 95% 0.72-0.95, p < 0.01). Considering both thresholds (the SI ≥ 1.76 together with the percentage of activated basophils > 5%) as diagnostic criteria, 15 patients had positive BAT, the overall BAT sensitivity being 68.18% (CI 95% 45.11-82.26%). None of the controls fulfilled both criteria and the specificity of the test was 100% (CI 95% 87.35-100%).

Conclusions

With a stimulation index ≥ 1.76 and a percentage of activated basophils > 5.01% as threshold, the performance of BAT for NMBAs yields 68.18% sensitivity and 100% specificity.

Update on the performance and application of basophil activation tests

The basophil activation test (BAT) is a flow-cytometry-based functional assay that assesses the degree of cell activation after exposure to a stimuli. Though no standardized technique currently exists, recent advances have improved the performance of this assay, including identification of new basophil-specific markers and comparisons of the expression of CD63 to CD203c during activation. The basophil activation test has also been validated for many IgE-mediated disease conditions, which have been extensively reviewed elsewhere. This review focuses on the most recent applications of this test to the diagnosis of allergy to drugs, foods, venoms, and pollens, and the evolving role of the BAT in monitoring immunotherapy.