Skin testing and drug challenge in the evaluation of drug hypersensitivity reactions

Non-IgE-Mediated Immediate Drug-Induced Hypersensitivity Reactions

Immediate drug-induced hypersensitivity reactions (IDHSRs) have conventionally been attributed to an immunoglobulin E (IgE)-mediated mechanism. Nevertheless, it has now been acknowledged that IDHSRs can also occur independently of IgE involvement. Non-IgE-mediated IDHSRs encompass the activation of effector cells, both mast cell-dependent and -independent and the initiation of inflammatory pathways through immunogenic and nonimmunogenic mechanisms. The IDHSRs involve inflammatory mediators beyond histamine, including the platelet-activating factor, which activates multiple cell types, including smooth muscle, endothelium, and MC, and evidence supports its importance in IgE-mediated reactions in humans. Clinically, distinguishing IgE from non-IgE mechanisms is crucial for future treatment strategies, including drug(s) restriction, readministration approaches, and pretreatment considerations. However, this presents significant challenges because certain drugs can trigger both mechanisms, and their presentations can appear similarly, ranging from mild to life-threatening symptoms. Thus, history alone is often inadequate for differentiation, and skin tests lack a standardized approach. Moreover, drug-specific IgE immunoassays have favorable specificity but low sensitivity, and the usefulness of the basophil activation test remains debatable. Lastly, no biomarker reliably differentiates between both mechanisms. Whereas non-IgE-mediated mechanisms likely predominate in IDHSRs, reclassifying most drug-related IDHSRs as non-IgE-mediated, with suggested prevention through dose administration adjustments, is premature and risky. Therefore, continued research and validated diagnostic tests are crucial to improving our capacity to distinguish between these mechanisms, ultimately enhancing patient care.

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.

A combined risk modeling strategy for clinical prediction of beta-lactam allergies in children

Background: Drug provocation test (DPT) without skin tests is increasingly recommended in the evaluation of children with low-risk beta-lactam (BL) allergies. However, risk definitions are unclear. Objective: The aim of this study was to compose a clinical predictive model that could identify the children at low risk who could safely undergo direct DPT. Methods: The clinical data of 204 children who underwent a full diagnostic algorithm for suspected BL allergy were analyzed. Clinical data were used to construct mathematical predictive model for confirmed BL allergies. A prospective new sample was used for external validation of the final model. Results: The presentations during the index reaction were anaphylaxis in 5.9% and cutaneous reactions in the majority. BL allergy was confirmed in 15.7% of suspected cases. A backward multiple logistic regression model showed that a family history of drug allergy (adjusted odds ratio [aOR], 5.52), anaphylaxis (aOR, 5.14), any atopic disease other than asthma (aOR, 4.38), and a reaction interval of 0-6 hours during the index reaction (aOR, 5.32) were significantly associated with a confirmed BL allergy. A mathematical combined model based on these factors showed a sensitivity of 77.8% and a negative predictive value (NPV) of 94.3%. The validation study replicated sensitivity and NPV values of the main cohort. Conclusion: The risk definition in BL allergies should depend on population-specific predictive models, including a combination of significant risk factors rather than empiric risk approaches. This may help to accurately determinate children at low risk who may safely proceed to direct DPT.