Skin Testing Approaches for Immediate and Delayed Hypersensitivity Reactions

Delayed Skin Testing for Systemic Medications: Helpful or Not?

Cutaneous adverse drug reactions collectively are delayed drug reactions such as morbilliform drug eruption and severe cutaneous adverse reactions (SCARs). Morbilliform drug eruption may wane over time, be the result of drug viral interactions, and be amenable to slow reintroduction or rechallenge, whereas SCARs are HLA class I restricted, T-cell-mediated reactions that demonstrate durable immunity and warrant lifelong avoidance. SCARs such as drug reaction with eosinophilia and systemic symptoms, Stevens-Johnson syndrome and toxic epidermal necrolysis, acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption often occur in the setting of multiple drugs dosed together. Collectively, they lead to significant morbidity, mortality, and drug safety concerns that could severely limit future treatment options. Currently, no single or combination of diagnostic tests for SCARs such as ex vivo or in vitro testing, in vivo (skin) testing, or other adjunctive tests such as HLA typing have 100% negative predictive value. In this "Controversies in Allergy Review" article, we review the current literature on delayed skin testing (patch and delayed prick/intradermal test) and critically assess the evidence base of its utility across different drugs and clinical phenotypes of delayed hypersensitivity reactions.

Effectiveness of Carboplatin-Prescreening Intradermal Skin Tests to Reduce Unanticipated Immediate Hypersensitivity Reactions: A Comparative Study

BACKGROUND

Carboplatin administration poses a risk of immediate hypersensitivity reactions (IHRs) that tend to increase with repeated administration and are mostly IgE-mediated.

OBJECTIVE

This study evaluated the usefulness of carboplatin-prescreening intradermal skin tests (IDTs).

METHODS

Carboplatin-prescreening IDTs were routinely conducted in patients with a history of receiving six or more carboplatin cycles beginning in January 2021. The primary objective was to assess disparities in the incidence of unanticipated IHRs to carboplatin administration. We compared patients in the intervention group (from 2021 to 2022) and those who did not undergo prescreening IDTs under the same conditions (preintervention group, from 2019 to 2020). Secondary objectives included evaluating the sensitivity and specificity of the prescreening IDT and the incidence of carboplatin IHR according to the number of infusion cycles.

RESULTS

The intervention group was composed of 67 patients who were administered 347 carboplatin cycles whereas the preintervention group included 96 patients who were administered 464 carboplatin cycles. The risk of unanticipated carboplatin IHRs decreased by 83.2% in the intervention group compared with results in the preintervention group (preintervention group, 3.45%, n = 16 vs intervention group, 0.58%, n = 2; P = .005). The prescreening IDT showed a sensitivity and specificity of 77.78% and 99.41%, respectively. The risk of newly developed IHRs based on the number of carboplatin cycles was less than 1% (cycles 1-5), 2.11% (cycle 6), 3.90% (cycles 7-12), 2.90% (cycles 13-18), and 0.74% (cycles 19 and greater), respectively.

CONCLUSIONS

Initiating carboplatin-prescreening IDTs from the seventh cycle on significantly reduced the risk of unanticipated IHRs.

EAACI/ENDA position paper on drug provocation testing

In drug hypersensitivity, drug provocation testing (DPT), also called drug challenge, is the gold standard for investigation. In recent years, risk stratification has become an important tool for adjusting the diagnostic strategy to the perceived risk, whilst still maintaining a high level of safety for the patient. Skin tests are recommended before DPT but may be omitted in low-risk patients. The task force suggests a strict definition of such low-risk patients in children and adults. Based on experience and evidence from studies of allergy to beta-lactam antibiotics, an algorithm on how to adjust DPT to the risk, and when to omit skin tests before DPT, is presented. For other antibiotics, non-steroidal anti-inflammatory drugs and other drugs, skin tests are poorly validated and DPT is frequently necessary. We recommend performing DPT with chemotherapeutics and biologicals to avoid unnecessary desensitization procedures and DPT with skin tests negative contrast media. We suggest DPT with anesthetics only in highly specialized centers. Specifics of DPT to proton pump inhibitors, anticonvulsants and corticosteroids are discussed. This position paper provides general recommendations and guidance on optimizing use of DPT, whilst balancing benefits with patient safety and optimizing the use of the limited available resources.

Updates in SJS/TEN: collaboration, innovation, and community

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN) is a predominantly drug-induced disease, with a mortality rate of 15-20%, that engages the expertise of multiple disciplines: dermatology, allergy, immunology, clinical pharmacology, burn surgery, ophthalmology, urogynecology, and psychiatry. SJS/TEN has an incidence of 1-5/million persons per year in the United States, with even higher rates globally. One of the challenges of SJS/TEN has been developing the research infrastructure and coordination to answer questions capable of transforming clinical care and leading to improved patient outcomes. SJS/TEN 2021, the third research meeting of its kind, was held as a virtual meeting on August 28-29, 2021. The meeting brought together 428 international scientists, in addition to a community of 140 SJS/TEN survivors and family members. The goal of the meeting was to brainstorm strategies to support the continued growth of an international SJS/TEN research network, bridging science and the community. The community workshop section of the meeting focused on eight primary themes: mental health, eye care, SJS/TEN in children, non-drug induced SJS/TEN, long-term health complications, new advances in mechanisms and basic science, managing long-term scarring, considerations for skin of color, and COVID-19 vaccines. The meeting featured several important updates and identified areas of unmet research and clinical need that will be highlighted in this white paper.

Diagnosis and selection of alternative antibiotics in beta-lactams hypersensitivity reactions: Current recommendations and challenges

Beta-lactam (BLM) antibiotics, including amino-penicillin and cephalosporins, are typically the first-choice treatment for bacterial infections. However, adverse reactions to these antibiotics are frequently reported, causing non-allergist physicians to select alternative broad-spectrum antibiotics that can have harmful consequences. Patients with unclear histories of hypersensitivity reactions to BLMs should undergo an allergy workup to establish a firm diagnosis, particularly when different drugs are prescribed simultaneously. However, finding the safest, most precise, and cost-effective methods for confirming BLMs hypersensitivity and selecting the most appropriate alternative BLM is uncertain, particularly in severe delayed reactions. This review aims to provide data and recommendations on the availability and validity of skin tests (STs), drug provocation test (DPT) protocols, based on the latest published literature and guideline. To make the process more practical, we focused on cross-reactivity between BLMs and diagnostic tests. There are two main novel aspects of this document: 1) For T-cell-mediated reactions, patient stratification into high, moderate, and low-risk groups based on the mortality and morbidity of adverse drug reactions. 2) For IgE-mediated reactions, stratification of individuals with isolated limited urticarial without anaphylaxis in a low-risk group and removal of the extensive limitation.

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.

Delabelling multiple antibiotic allergy: Practical issues

With the growing incidence of multi-drug resistant organisms, delabelling incorrect antibiotic allergies has become an integral part of antimicrobial stewardship worldwide. For example, around 90% of penicillin allergy labels are found to be inaccurate following a full allergy work-up, which deprive patients the use of effective first-line penicillin antibiotics and increase the risk of antimicrobial resistance with the use of other extended spectrum non-penicillin antimicrobials. Significant numbers of adult and paediatric patients over time are labelled with multiple penicillin and non-penicillin antibiotic allergies often during inappropriate antimicrobial use, resulting in a label of “multiple antibiotic allergy”. In contrast to delabelling penicillin allergy where oral direct provocation tests can be used for low-risk, mild reactions, and sensitivity/specificity/positive and negative predictive values of skin tests have been demonstrated, diagnostic tests for multiple antibiotic allergy often require the use of a combination of in-vivo and in-vitro tests across different antimicrobial classes for evaluation. Shared decision making with patients and informed consent are also needed when prioritising which drugs to delabel first, balancing the risks, benefits of testing vs. interim use of alternative antibiotics. Similar to delabelling penicillin allergy, the cost-effectiveness of delabelling multiple drug allergies is unknown.

A multidisciplinary approach to verify and de-label of drug allergic histories in a university hospital in Thailand: a retrospective descriptive study

BACKGROUND

Mislabeling of drug allergic histories causes avoidable negative impacts on patients and healthcare system. Although multidisciplinary adverse drug reaction (ADR) services to verify and de-label drug allergic histories have been operated in particular hospitals in Thailand, their performances have not been reported. This research aimed to examine the effectiveness of verification of drug allergic history and de-labeling (VD) services of the physician-led multidisciplinary ADR clinic.

METHODS

This research was a retrospective descriptive study. Medical charts of patients with at least one drug allergic history who received VD services at the multidisciplinary clinic between January 2017 to December 2018, were reviewed. Data on the history of drug allergy, VD services, and results were analyzed and presented using descriptive statistics.

RESULTS

Seventy patients' charts were reviewed, and 171 unconfirmed drug allergic histories were identified. 79.53% of the reported reactions involved skin and soft tissues. The most found adverse skin reactions were maculopapular rash, pruritic and erythematous rash, and angioedema. The remaining 20.47% were systemic reactions which included drug reaction with eosinophilia and systemic symptoms (DRESS), anaphylaxis, and nausea/vomiting was the most prevalent. Antituberculosis, beta-lactam antibiotics, and nonsteroidal anti-inflammatory drugs (NSAIDs) were the most reported suspected drugs. Drug allergic history reviewing by physicians or pharmacists could confirm and de-label for 3 and 20 reactions, respectively. Seven and one reactions were confirmed by enzyme-linked immunospot assay and patch test, respectively. The provocation tests with the suspected or alternative drug were conducted in 64 reactions. Twelve reactions were confirmed, and 45 reactions were de-labeled. Totally, 65/171 (38.01%) allergic histories were successfully de-labeled, 23/171 (13.45%) were confirmed, and 83/171 (48.53%) were inconclusive.

CONCLUSIONS

More than half of drug allergic histories were successfully confirmed or de-labeled by the multidisciplinary ADR team. The collaborative activities of various healthcare professionals, consisting of physicians, nurse, and pharmacists as presented in the study were effective in VD services and should be implemented in other healthcare settings.

Advances in immunoglobulin E mediated antibiotic allergy

PURPOSE OF REVIEW

The purpose of this review is to identify recent advances in our understanding and management of immunoglobulin E (IgE)-mediated antibiotic allergy.

RECENT FINDINGS

Antibiotics remain a leading cause of fatal anaphylaxis reported to the FDA. However, recent advances have defined the features of adult and pediatric patients without true IgE-mediated allergy or any mechanism of anaphylaxis when tested. This has created opportunities to use direct challenges to disprove these allergies at the point-of-care and improves antibiotic stewardship. Additional advances have highlighted cross-reactive structural considerations within classes of drugs, in particular the R1 side-chain of cephalosporins, that appear to drive true immune-mediated cross-reactivity. Further advances in risk-based approaches to skin testing, phenotyping, and re-exposure challenges are needed to standardize antibiotic allergy evaluation.

SUMMARY

Recent advances in defining true IgE-mediated drug allergy have helped to identify patients unlikely to be skin-test positive. In turn, this has identified patients who can skip skin testing and proceed to direct ingestion challenge using history risk-based approaches. The ability to identify the small number of patients with true IgE-mediated allergy and study their natural history over time, as well as the vast majority without true allergy will facilitate important and novel mechanistic discoveries.

Confirmation of Drug Allergy in a General Pediatrics Outpatient Clinic

BACKGROUND

The studies including diagnostic workup on true drug allergy in children are limited.

OBJECTIVE

This study aimed to evaluate the frequency of confirmed drug allergies in children with a history of suspected drug allergies who had applied to the general paediatric outpatient clinics of our hospital due to various health problems.

METHODS

The history of drug allergy was questioned in children who applied to the general pediatric outpatient clinics of our hospital. Allergy tests were performed to confirm drug allergy in children whose history was compatible with drug allergy.

RESULTS

In this study, the parents of 5,553 children aged between 4 months and 17.9 years were asked, "Has your child ever developed an allergy after drug use?". Seven percent of parents (n=389/5,553) thought that their child had a drug allergy. When these patients were evaluated by a paediatric allergist, it was suspected that 21.1% (n=82/389) had a drug allergy. When diagnostic tests were performed for drug allergies, drug allergy was confirmed in only 4.2% (n=3/72). As a result, the frequency of drug allergies according to the history was 1.47% (n=82/5,553) in the population we studied, while the frequency of confirmed drug allergies was found to be 0.05% (n=3/5,553).

CONCLUSION

The patient and/or parent statements alone are not sufficient for the diagnosis of drug allergies in children. In order to confirm or rule out drug allergies, drug allergy tests must be performed and so unnecessary drug restrictions can be avoided.