The in vitro diagnosis of drug allergy: status and perspectives

Metformin-induced hepatitis; paliperidone-related peripheral edema; vasospastic angina induced by oral capecitabine; skin hyperpigmentation due to long-term voriconazole therapy; vaccine-associated measles

The purpose of this feature is to heighten awareness of specific adverse drug reactions (ADRs), discuss methods of prevention, and promote reporting of ADRs to the US Food and Drug Administration's (FDA's) MedWatch program (800-FDA-1088). If you have reported an interesting, preventable ADR to MedWatch, please consider sharing the account with our readers. Write to Dr. Mancano at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-707-4936; e-mail: mmancano@temple.edu). Your report will be published anonymously unless otherwise requested. This feature is provided by the Institute for Safe Medication Practices (ISMP) in cooperation with the FDA's MedWatch program and Temple University School of Pharmacy. ISMP is an FDA MedWatch partner.

Cellular in vitro diagnosis of adverse drug reactions

Adverse drug reactions can manifest clinically in a variety of ways. Whilst the majority can be explained by dose-dependent side effects, there is group of unpredictable immunological or non-immunological intolerances that represent a particular diagnostic challenge. Skin tests are frequently negative, whilst challenge tests are time-consuming and often hazardous. Against this backdrop, cellular in vitro tests play a particularly important role in the identification of the causative drug. Whilst basophil tests can be used in the case of immunoglobulin E (IgE)- as well as non-IgE-mediated hypersensitivity reactions, T-cellular test methods assist in the diagnosis of drug eruptions. The reliability of individual tests can be affected by a variety of parameters, such as the pathomechanism underlying the drug reaction, the causative medication, or the point in time of testing. Not only is a sound knowledge of the basic principles of the individual assays an essential prerequisite for correctly indicating and interpreting this test method, but also an awareness of these additional factors.

In vitro diagnosis of immediate IgE-mediated drug hypersensitivity: warnings and (unmet) needs

Immediate drug hypersensitivity reactions (DHR) constitute an important health condition, with serious consequences of inadequate diagnosis. In this article, some of the most important issues related to in vitro diagnosis of IgE-mediated allergies are discussed. In vitro diagnostics will benefit from expanded and novel insights and understandings in drug chemical reactivity, protein binding, biotransformation, degradation, identification of (cross-reactive) drug antigenic determinants, and deeper understanding of sensitization routes. Collective efforts should be undertaken to activate fundamental and clinical investigations.

International Consensus on drug allergy

When drug reactions resembling allergy occur, they are called drug hypersensitivity reactions (DHRs) before showing the evidence of either drug-specific antibodies or T cells. DHRs may be allergic or nonallergic in nature, with drug allergies being immunologically mediated DHRs. These reactions are typically unpredictable. They can be life-threatening, may require or prolong hospitalization, and may necessitate changes in subsequent therapy. Both underdiagnosis (due to under-reporting) and overdiagnosis (due to an overuse of the term ‘allergy’) are common. A definitive diagnosis of such reactions is required in order to institute adequate treatment options and proper preventive measures. Misclassification based solely on the DHR history without further testing may affect treatment options, result in adverse consequences, and lead to the use of more-expensive or less-effective drugs, in contrast to patients who had undergone a complete drug allergy workup. Several guidelines and/or consensus documents on general or specific drug class-induced DHRs are available to support the medical decision process. The use of standardized systematic approaches for the diagnosis and management of DHRs carries the potential to improve outcomes and should thus be disseminated and implemented. Consequently, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), formed by the European Academy of Allergy and Clinical Immunology (EAACI), the American Academy of Allergy, Asthma and Immunology (AAAAI), the American College of Allergy, Asthma and Immunology (ACAAI), and the World Allergy Organization (WAO), has decided to issue an International CONsensus (ICON) on drug allergy. The purpose of this document is to highlight the key messages that are common to many of the existing guidelines, while critically reviewing and commenting on any differences and deficiencies of evidence, thus providing a comprehensive reference document for the diagnosis and management of DHRs.

Atopic dermatitis and skin allergies - update and outlook

During the last few years, an impressive amount of experimental studies and clinical trials have dealt with a variety of distinct topics in allergic skin diseases - especially atopic dermatitis. In this update, we discuss selected recent data that provide relevant insights into clinical and pathophysiological aspects of allergic skin diseases or discuss promising targets and strategies for the future treatment of skin allergy. This includes aspects of barrier malfunction and inflammation as well as the interaction of the cutaneous immune system with the skin microbiome and diagnostic procedures for working up atopic dermatitis patients. Additionally, contact dermatitis, urticaria, and drug reactions are addressed in this review. This update summarizes novel evidence, highlighting current areas of uncertainties and debates that will stimulate scientific discussions and research activities in the field of atopic dermatitis and skin allergies in the future.

Hypersensitivity reactions to non beta-lactam antimicrobial agents, a statement of the WAO special committee on drug allergy

Antibiotics are used extensively in the treatment of various infections. Consequently, they can be considered among the most important agents involved in adverse reactions to drugs, including both allergic and non-allergic drug hypersensitivity [J Allergy Clin Immunol 113:832–836, 2004]. Most studies published to date deal mainly with reactions to the beta-lactam group, and information on hypersensitivity to each of the other antimicrobial agents is scarce. The present document has been produced by the Special Committee on Drug Allergy of the World Allergy Organization to present the most relevant information on the incidence, clinical manifestations, diagnosis, possible mechanisms, and management of hypersensitivity reactions to non beta-lactam antimicrobials for use by practitioners worldwide.

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.

Threshold for positivity and optimal dipyrone concentration in flow cytometry-assisted basophil activation test

Purpose

Basophil activation occurs both in patients with immediate hypersensitivity reactions to anti-inflammatory drugs and in healthy controls in a dose-dependent manner. Our aims were to define the optimal basophil activation test (BAT) concentration and the threshold for BAT positivity for dipyrone.

Methods

From 45 patients with a positive history of an immediate hypersensitivity reaction to dipyrone, we found 20 patients with dipyrone-induced anaphylaxis demonstrating positive skin tests. All selected patients, as well as 10 healthy controls, were tested in vivo and in vitro. BAT was performed using Flow 2CAST technique with three low dipyrone concentrations: 25 µg/mL (c1), 2.5 µg/mL (c2) and 0.25 µg/mL (c3). The threshold for BAT positivity was established using receiver operating characteristics (ROC) curve analysis.

Results

Using ROC curve analysis the highest area under curve, 0.79 (0.63-0.95) (P<0.01), was found for c3. When the highest stimulation indexes from the three concentrations for each patient were used, ROC curve analysis revealed an area under curve of 0.81 (0.65-0.96) (P<0.01), sensitivity and specificity were 0.70 and 1 and the optimal threshold value for BAT positivity was 1.71. Thirteen patients had a positive BAT for at least one of the tested dipyrone concentrations. All healthy controls presented negative BAT.

Conclusions

BAT might be a useful technique to diagnose dipyrone allergy, provided all three low dipyrone concentrations are used together. With an assay-specific threshold of 1.71, ROC curve analysis yields 70% sensitivity and 100% specificity.