Diagnosing immune-mediated reactions to drugs

An Updated Review of the Diagnostic Methods in Delayed Drug Hypersensitivity

Delayed drug hypersensitivity reactions are clinically diverse reactions that vary from isolated benign skin conditions that remit quickly with no or symptomatic treatment, drug discontinuation or even continued drug treatment, to the other extreme of severe cutaneous adverse reactions (SCARs) that are associated with presumed life-long memory T-cell responses, significant acute and long-term morbidity and mortality. Diagnostic "in clinic" approaches to delayed hypersensitivity reactions have included patch testing (PT), delayed intradermal testing (IDT) and drug challenges for milder reactions. Patch and IDT are, in general, performed no sooner than 4-6 weeks after resolution of the acute reaction at the maximum non-irritating concentrations. Functional in vitro and ex vivo assays have largely remained the province of research laboratories and include lymphocyte transformation test (LTT) and cytokine release enzyme linked ImmunoSpot (ELISpot) assay, an emerging diagnostic tool which uses cytokine release, typically IFN-γ, after the patient's peripheral blood mononuclear cells are stimulated with the suspected drug(s). Genetic markers such as human leukocyte antigen have shown recent promise for both pre-prescription screening as well as pre-emptive and diagnostic testing strategies.

Severe cutaneous adverse reactions induced by targeted anticancer therapies and immunotherapies

With the increasing use of targeted anticancer drugs and immunotherapies, there have been a substantial number of reports concerning life-threatening severe cutaneous adverse reactions (SCARs), including Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug rash with eosinophilia and systemic symptoms, drug-induced hypersensitivity syndrome, and acute generalized exanthematous pustulosis. Although the potential risks and characteristics for targeted anticancer agent- and immunotherapy-induced SCAR were not well understood, these serious adverse reactions usually result in morbidity and sequela. As a treatment guideline for this devastating condition is still unavailable, prompt withdrawal of causative drugs is believed to be a priority of patient management. In this review, we outline distinct types of SCARs caused by targeted anticancer therapies and immunotherapies. Also, we discuss the clinical course, latency, concomitant medication, tolerability of rechallenge or alternatives, tumor response, and mortality associated with these devastating conditions. Imatinib, vemurafenib, and rituximab were the top three offending medications that most commonly caused SJS/TEN, while EGFR inhibitors were the group of drugs that most frequently induced SJS/TEN. For drug rash with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome and acute generalized exanthematous pustulosis, imatinib was also the most common offending drug. Additionally, we delineated 10 SCAR cases related to innovative immunotherapies, including PD1 and CTLA4 inhibitors. There was a wide range of latency periods: 5.5–91 days (median). Only eight of 16 reported patients with SCAR showed clinical responses. Targeted anticancer drugs and immunotherapies can lead to lethal SCAR (14 deceased patients were identified as suffering from SJS/TEN). The mortality rate of TEN was high: up to 52.4%. The information compiled herein will serve as a solid foundation to formulate ideas for early recognition of SCAR and to discontinue offending drugs for better management.

An Updated Review of the Molecular Mechanisms in Drug Hypersensitivity

Drug hypersensitivity may manifest ranging from milder skin reactions (e.g., maculopapular exanthema and urticaria) to severe systemic reactions, such as anaphylaxis, drug reactions with eosinophilia and systemic symptoms (DRESS)/drug-induced hypersensitivity syndrome (DIHS), or Stevens–Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN). Current pharmacogenomic studies have made important strides in the prevention of some drug hypersensitivity through the identification of relevant genetic variants, particularly for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). The associations identified by these studies are usually drug, phenotype, and ethnic specific. The drug presentation models that explain how small drug antigens might interact with HLA and T cell receptor (TCR) molecules in drug hypersensitivity include the hapten theory, the p-i concept, the altered peptide repertoire model, and the altered TCR repertoire model. The broad spectrum of clinical manifestations of drug hypersensitivity involving different drugs, as well as the various pathomechanisms involved, makes the diagnosis and management of it more challenging. This review highlights recent advances in our understanding of the predisposing factors, immune mechanisms, pathogenesis, diagnostic tools, and therapeutic approaches for drug hypersensitivity.

Recent advances in the understanding of severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs) encompass a heterogeneous group of delayed hypersensitivity reactions, which are most frequently caused by drugs. Our understanding of several aspects of SCAR syndromes has evolved considerably over the last decade. This review explores evolving knowledge of the immunopathogenic mechanisms, pharmacogenomic associations, in vivo and ex vivo diagnostics for causality assessment, and medication cross-reactivity data related to SCAR syndromes. Given the rarity and severity of these diseases, multidisciplinary collaboration through large international, national and/or multicentre networks to collect prospective data on patients with SCAR syndromes should be prioritized. This will further enhance a systematized framework for translating epidemiological, clinical and immunopathogenetic advances into preventive efforts and improved outcomes for patients.

In Vitro Research Tools in the Field of Human Immediate Drug Hypersensitivity and Their Present Use in Small Animal Veterinary Medicine

Drug hypersensitivity reactions (DHR) are immune-mediated idiosyncratic adverse drug events. Type I DHR are often referred to as "immediate" and involve B lymphocyte-secreted IgE that bind to the membrane of basophils and mast cells, inducing their degranulation. This review presents various in vitro tests that were developed in the field of human type I HS and implemented as clinical diagnostic tools in human cases of immediate DHR. The respective strengths and weaknesses of each test will be discussed in parallel of validation data such as specificity and sensitivity whenever available. Some of them have also been used as diagnostic tools in veterinary medicine, but not in cases of immediate DHR. Most of these diagnostic tools can be categorized into humoral and cellular tests. The former tests measure serum concentrations of factors, such as histamine, tryptase, and drug-specific IgE. The latter assays quantify markers of drug-induced basophil activation or drug-specific lymphocyte proliferation. Pharmacogenetic markers have also been investigated in immediate DHR, but not as extensively as in non-immediate ones. Throughout, practical aspects and limitations of the tests, as well as sensitivity and specificity parameters, will be presented. In addition, the experience of veterinary medicine with these diagnostic tools will be summarized. However, to date, none of them has ever been reported in a veterinary case of type I DHR.

Severe Cutaneous Adverse Reactions: The Pharmacogenomics from Research to Clinical Implementation

Severe cutaneous adverse reactions (SCARs), previously thought to be idiosyncratic or unpredictable, are a deadly form of adverse drug reactions with skin manifestations. Current pharmacogenomic studies of SCARs have made important strides, as the prevention of SCARs, to some extent, appears attainable with the identification of genetic variants for genes encoding drug-metabolizing enzymes and human leukocyte antigens (HLAs). Despite the improvement of incidence, a treatment guideline for this devastating condition is still unavailable, highlighting the inadequacy of contemporary accepted therapeutic interventions. As such, prompt withdrawal of causative drugs is believed to be a priority of patient management. In this review, we discuss recent cutting-edge findings concerning the discovery of biomarkers for SCARs and their clinical utilities in the better prediction and early diagnosis of this disease. The knowledge compiled herein provides clues for future investigations on deciphering additional genetic markers for SCARs and the design of clinical trials for the prospective identification of subjects at genetic risk for this condition, ultimately personalizing the medicine.

Antimicrobial stewardship's new weapon? A review of antibiotic allergy and pathways to 'de-labeling'

PURPOSE OF REVIEW

The continued emergence of multiresistant pathogens and widespread antimicrobial use has led to a greater emphasis on antimicrobial stewardship programs. Concurrently, an increased awareness of the rising number of antibiotic allergy labels and impact on antimicrobial use has surfaced. The integration of antibiotic allergy de-labeling and antimicrobial stewardship programs may be a pathway worthy of further focus and investigation.

RECENT FINDINGS

Recent literature has evaluated the efficacy of antibiotic allergy management (historical de-labeling, in-vitro testing, skin prick testing, intradermal testing, and oral challenges) and impact of antibiotic allergy labels on patient outcome. The importance of true and perceived antibiotic allergy cross-reactivity in the setting of β-lactam allergies has been highlighted. The impact of dedicated antibiotic allergy de-labeling clinics, inpatient antibiotic allergy testing, and integrated antimicrobial stewardship programs has been recently appraised.

SUMMARY

More recent literature supports that appropriate antibiotic allergy in-vitro and in-vivo testing and subsequent antibiotic allergy de-labeling, particularly in regard to β-lactams, can decrease broad-spectrum antibiotic use, costs, patient length of stay, and mortality. Integration of antibiotic allergy management into the decision support systems of inpatient and outpatient antimicrobial stewardship programs represents an important opportunity to further improve measured outcomes from antibiotic utilization.

Predictive value of the lymphocyte toxicity assay in the diagnosis of drug hypersensitivity syndrome

BACKGROUND

Drug hypersensitivity syndrome (DHS) is a rare but potentially fatal adverse drug reaction that develops in susceptible patients following exposure to certain drugs. Because of the variable clinical picture of DHS and its resemblance to other diseases, the diagnosis of DHS is challenging. The lymphocyte toxicity assay (LTA) is an in vitro test that has been used in the diagnosis of DHS. However, its predictive values are still controversial because of the lack of a 'gold standard' test to measure it against.

OBJECTIVES

To determine the sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of the LTA in the diagnosis of DHS due to different classes of drugs, based on systemic re-exposure as a gold standard, and to evaluate the current clinical utility of the LTA in clinical practice.

METHODS

Potential participants were identified from their medical records and contacted to obtain their consent to participate in the study. One hundred forty-seven patients were recruited and interviewed by telephone to identify events of re-exposure and their consequences. These data were used to determine true positive, false positive, true negative, and false negative results of the test, which were then used to estimate the predictive value of the test.

RESULTS

We identified 26 re-exposure events in 22 patients: 4 were true positives, 17 were true negatives, 1 was a false positive, and 4 were false negatives, as determined by systemic re-exposure. Although the number of identified re-exposures limited the ability to calculate the predictive values, our data provide an estimate of the clinical value of the test for the diagnosis of DHS. The data also highlight the effect of the type of drug involved in the reaction on the predictive value of the test.

CONCLUSION

The LTA is potentially a valuable diagnostic tool for DHS; however, its sensitivity, specificity, NPV, and PPV seem to vary according to the drug involved in the reaction.

Autism spectrum disorders and allergy: observation from a pediatric allergy/immunology clinic

IgE-mediated allergic diseases (e.g., allergic rhinoconjunctivitis, atopic asthma and food allergy) are prevalent (up to 30%) in the general population and are increasing in developed countries. In infants and young children, non-IgE-mediated food allergy is also prevalent. In addition to easily recognized organ-specific symptoms, allergic diseases can cause neuropsychiatric symptoms, such as irritability and hyperactivity, in otherwise healthy individuals. This is also likely to occur in children with autism spectrum disorder (ASD). Moreover, the discomfort and pain associated with allergic diseases could aggravate behavioral symptoms in ASD children. Allergic conditions are easily treatable; however, ASD children may be underdiagnosed and/or undertreated for allergic and other common childhood diseases, in part due to their impaired communication skills. Practicing physicians should be aware of the potential impact of allergic diseases on behavioral symptoms and cognitive activity in ASD children. However, they also need to be aware that certain symptoms often attributed to 'allergy' by caregivers may not be immune mediated and should understand that behavioral symptoms can also be affected by many non-IgE-mediated causes.