Drug allergy diagnosis in humans: possibilities and pitfalls

Bridging the gap between bench and clinic: the importance of understanding the mechanism of iodinated contrast media hypersensitivity

Since the advent of CT, iodinated contract media (ICM) has become one of the most regularly administered intravenous medications in clinical settings. Although considered generally safe, ICM is one of the most common causes of adverse drug reactions in clinical practice, accounting for more than 2 million adverse reactions worldwide. Currently, there are few useful tools to diagnose patient hypersensitivity, with the major limitation being the lack of consensus regarding the mechanisms of hypersensitivity to ICM. While there is an overwhelming abundance of literature pertaining to clinical features including incidence, symptomatology, and risk, few studies have further investigated the underlying mechanisms behind their clinical observations. Of the available literature discussing pathophysiology, most primary studies were completed over 20 years ago, since which the molecular characteristics of ICM have changed. Furthermore, many reviews mentioning pathophysiology fail to adequately emphasize the clinical importance of understanding the molecular pathways involved in hypersensitivity. In this review, we aim to emphasize the clinical relevance of pathophysiology as it relates to the prediction and diagnosis of hypersensitivity reactions to ICM. To this end, we will first briefly characterize hypersensitivity reactions to ICM with respect to epidemiology and clinical presentation. We will then present the existing evidence supporting various proposed mechanisms of hypersensitivity, highlighting the gaps that remain in the mechanistic delineation of both immediate and delayed reactions. Finally, we discuss the possibility of in vitro testing as a way to predict and diagnose hypersensitivity reactions, pending a more complete elucidation of mechanisms.

Assessment of Opioid Cross-reactivity and Provider Perceptions in Hospitalized Patients With Reported Opioid Allergies

Background: The incidence of opioid allergy cross-reactivity in hospitalized patients with historical opioid allergies remains unknown. Objectives: The purpose of this study was to characterize the incidence of newly suspected IgE-mediated reactions (IMRs) based on clinical criteria among patients with a chart-documented opioid allergy and to assess clinician perceptions of opioid allergies. Methods: This retrospective cohort study was conducted in hospitalized adults with a historically documented opioid allergy who received a subsequent opioid. The primary outcome was the incidence of allergic cross-reactivity between clinical and chemical opioid classes in patients with historical IMRs (H-IMRs) identified by clinical criteria, ICD-9 diagnosis codes, or allergic reaction treatment. Secondary outcomes included the incidence of opioid intolerances incorrectly documented as allergies and a survey to clinicians to assess the impact of opiate warnings on prescribing practices. Results: A total of 499 patients with historical opioid allergies were included. H-IMR to an opioid of any class was not significantly associated with IMR cross-reactivity to the same or any other class, with cross-reactivity rates ranging from 0% to 6.7%. Of the historical chart-documented allergies, 249 reactions (50%) were determined to be intolerances. A total of 461 (92.5%) patients successfully tolerated readministration of opioids despite a chart-documented allergy, and 8 (1.6%) patients developed possible IMR (7 pruritus, 1 possible anaphylaxis). Survey results (n = 54) indicated that opiate allergy warnings were neutral or unlikely to change opiate prescribing. Conclusions: The risk of IMRs caused by opioids is low in patients with H-IMRs to opioids. Opioid allergy documentations may propagate alert fatigue and unwarranted prescribing changes.

Bullous Pemphigoid with Atypical Skin Lesions and Acute Interstitial Nephritis: A Case Report and Focused Literature Review

Patient: Male, 76

Final Diagnosis: Drug induced bullous pemphigoid

Symptoms: Skin rash

Medication: Cephalexin

Clinical Procedure: Skin biopsy

Specialty: General and Internal Medicine

Eosinophilic infiltrate in a patient with severe Legionella pneumonia as a levofloxacin-related complication: a case report

Introduction

Legionella pneumonia can appear with different levels of severity and it can often present with complications such as acute respiratory distress syndrome.

Case presentation

We report the case of a 44-year-old Caucasian man with Legionella pneumonia with successive development of severe acute respiratory distress syndrome. During his stay in intensive care the clinical and radiological situation of the previously observed acute respiratory distress syndrome unexpectedly worsened due to acute pulmonary eosinophilic infiltrate of iatrogenic origin.

Conclusion

Levofloxacin treatment caused the occurrence of acute eosinophilic infiltrate. Diagnosis was possible following bronchoscopic examination using bronchoaspirate and transbronchial biopsy.

Characterising vancomycin's immunotoxic profile using Swiss and CFW mice as an experimental model

Immunotoxicology can lead to determining the adverse effects of different compounds on the immune system. Sometimes, many drugs (especially antibiotics) induce immune alterations, mainly auto-immunity. This study was aimed at determining vancomycin's immunotoxic effect by comparing the original molecule to two of the most used copies. Thirty-two mice from two murine strains (Swiss and CFW) were treated with three antibiotic formulations for studying its effect on splenic lymphoid and peripheral blood cell populations by using haemograms, flow cytometry and blastogenesis assays. The results indicated that vancomycin produces neutropenia and lymphocytosis in peripheral populations and that it induces a selective immunomodulatory effect on splenocyte sub-populations, depending on formulation and the strain so treated.

[Diagnostic methods for confirming drug-allergy--the lymphocyte transformation test in dermatology]

Recognizing the adverse drug reactions and confirming the role of the drug causing the symptoms is a great challenge for a medical team. The aim of this article is to review the diagnostic methods for confirming drug-allergy and to evaluate the lymphocyte transformation test according to dermatological aspect. Lymphocyte transformation test relies on the observation that specific T-cells divide and expand after encountering the antigen. T-cell sensitization is measured by 3H-thymidine uptake in dividing cells. The main advantage of this test is its applicability with many different drugs in different immune reactions, as drug-specific T-cells are almost always involved in drug hypersensitivity reactions. Its disadvantage is that the test is cumbersome and technically demanding. The method is not unequivocally accepted, it is necessary to carry out a systematic evaluation of its sensitivity and specificity to make the test more widely appreciated. Despite of its deficits, the lymphocyte transformation test plays an important role in diagnosing drug-hypersensitivities.

Mefloquine-induced eosinophilic pneumonia

Mefloquine has been widely used for prophylaxis and treatment of patients with chloroquine-resistant malaria; the drug is usually well tolerated. Rarely, adverse effects may be severe, including gastrointestinal disturbances, neuropsychiatric reactions, cardiovascular manifestations, skin lesions, musculoskeletal symptoms, and bone marrow toxicity. We describe a 67-year-old woman with fever, dyspnea on exertion, peripheral blood eosinophilia, and diffuse pulmonary infiltrates on chest radiography. She had taken mefloquine for malaria prophylaxis for an 8-week trip to South Africa. A thorough work-up led to the diagnosis of eosinophilic pneumonia caused by the mefloquine. Her condition improved after the drug was discontinued. To our knowledge, this is the first report of mefloquine-induced eosinophilic pneumonia. Clinicians should be aware of this rare, potential adverse effect of mefloquine.

Methods of evaluating immunotoxicity

Immunotoxicology is an important aspect of the safety evaluation of drugs and chemicals. Immunosuppression, (unspecific) immunostimulation, hypersensitivity and autoimmunity are the four types of immune-mediated adverse effects. However, the nonclinical assessment of immunotoxicity is at present often restricted to animal models and assays to predict unexpected immunosuppression. There is, however, no general consensus that a variety of assays can be considered depending on the compound to be tested. A major issue is whether histological examination of the thymus, spleen, lymphoid organs and Peyer's patches is a reliable predictor of immunosuppression or whether immune function should also be assessed. A T-dependent antibody response assay, either the plaque-forming cell assay or anti-keyhole limpet haemocyanin enzyme-linked immunosorbant assay, is recommended as a first-line assay. A variety of assays, including lymphocyte subset analysis, natural killer-cell activity, lymphocyte proliferation, delayed-type hypersensitivity, cytotoxic T-lymphocyte activity and macrophage/neutrophil function assays, can also be used. In certain circumstances, host resistance assays can be considered. With the exception of contact sensitisation, very few animal models and assays can reliably predict the potential for (unspecific) immunostimulation, hypersensitivity or autoimmunity. A major limitation of immunotoxicity risk assessment is the lack of human data. Immunological end points and clinical criteria to be included in clinical trials and epidemiological studies have to be carefully standardised and validated.

Sulfonamide allergies and outcomes related to use of potentially cross-reactive drugs in hospitalized patients

STUDY OBJECTIVES

To characterize patient-reported sulfonamide allergies, assess the influence of these allergies on drug prescribing practices, and determine the frequency and nature of adverse reactions in patients with sulfonamide allergies who receive potentially cross-reactive drugs.

DESIGN

Prospective observational study.

SETTING

Tertiary care hospital.

PATIENTS

Ninety-four hospitalized adult patients with reported sulfonamide allergies.

MEASUREMENTS AND MAIN RESULTS

Patients were followed during their hospital stay to document prescribing of and adverse reactions to sulfonamide antibiotics and sulfonamide nonantibiotics. Allergy characteristics and prescribing of sulfonamide-containing drugs were analyzed with descriptive statistics. Trimethoprim-sulfamethoxazole (TMP-SMX) allergy was reported by 42 patients (45%), whereas 42 patients (45%) did not recall the drug to which they were allergic. Fifty-nine patients (63%) reported the allergy's physical manifestation as rash, 13 (14%) anaphylaxis, and 2 (2)% Stevens-Johnson's syndrome. Median time since last reported allergic reaction to a sulfonamide-containing agent was 20 years. Forty patients (43%) had been taking a sulfonamide nonantibiotic as an outpatient for an average of 6.2 years; 24 (60%) of those patients took furosemide. Sixteen (40%) of the patients receiving sulfonamide nonantibiotics reported an allergy to TMP-SMX. Nine patients (10%) with no past sulfonamide nonantibiotic use received a sulfonamide nonantibiotic as an inpatient, with furosemide most commonly prescribed. No adverse events were reported before admission or observed during the inpatient stay (range 2-23 days).

CONCLUSIONS

Inpatient and outpatient use of potentially cross-reactive drugs was observed in 52% of patients, although numerous patients were unable to give an accurate allergy history. No adverse effects were reported or documented with outpatient or inpatient sulfonamide nonantibiotic use, even among patients with histories of life-threatening reactions to sulfonamides.

Eosinophilia: secondary, clonal and idiopathic

Blood eosinophilia signifies either a cytokine-mediated reactive phenomenon (secondary) or an integral phenotype of an underlying haematological neoplasm (primary). Secondary eosinophilia is usually associated with parasitosis in Third World countries and allergic conditions in the West. Primary eosinophilia is operationally classified as being clonal or idiopathic, depending on the respective presence or absence of a molecular, cytogenetic or histological evidence for a myeloid malignancy. The current communication features a comprehensive clinical summary of both secondary and primary eosinophilic disorders with emphasis on recent developments in molecular pathogenesis and treatment.

Tryptase as Severity Marker in Drug Provocation Tests

BACKGROUND

In the absence of objective symptoms, it is difficult to assess an adverse reaction during drug provocation testing. We evaluated the value of serum tryptase levels to distinguish between positive, negative and, even more important, so-called 'hysterical' reactions (conversion symptoms). The latter are occasionally observed in drug provocation tests when the patient experiences ambiguous subjective symptoms.

METHODS

In a prospective single-center study, 303 patients underwent 785 drug provocation tests. Blood was taken for tryptase measurement on each test day before and after drug challenge, and the changes in serum tryptase levels in patients with no reactions were compared with those who experienced immediate reactions to a drug.

RESULTS

Thirty-four of 785 drug provocations were clinically judged as being positive. Despite objective symptoms, median serum tryptase values in the afternoon were even lower than baseline levels. However, this decrease was not statistically significant. In the 751 patients suffering no objective reactions, the median values of post-testing tryptase values were statistically significantly decreased as compared with pretesting values.

CONCLUSIONS

The measurement of serum tryptase levels does not appear to be helpful to differentiate mild allergic or nonallergic reactions from 'hysterical' ones. The milder decrease in the group with objective drug reactions might indicate slight mast cell activation in some patients. More severe clinical drug reactions led to stronger mast cell degranulation. Mild reactions did not increase the tryptase levels consistently.

Immunotoxicology: role in the safety assessment of drugs

The immunotoxic effects of drugs are divided into immunosuppression, immunostimulation, hypersensitivity and autoimmunity. The major adverse consequences of immunosuppression are infectious complications and virus-induced malignancies. Flu-like reactions, more frequent autoimmune diseases and hypersensitivity reactions to unrelated allergens, and inhibition of drug-metabolising enzymes are the adverse effects related to immunostimulation. Hypersensitivity reactions are the most frequent immunotoxic effects of drugs. They include immune-mediated ('allergic') and non immune-mediated ('pseudoallergic') reactions. Drug-induced autoimmune reactions, either systemic or organ-specific, are seemingly rare. A review of drug-induced immunotoxic effects demonstrates that immunotoxicity is a significant cause of morbidity and even mortality. As immunotoxicologists have long focused on immunosuppression, the nonclinical immunotoxicity safety assessment of unexpected immunosuppression is based on a number of relatively well standardised and validated animal models and assays. However, there is no general consensus regarding the minimal requirement for this assessment. Many different assays can be used to extend the assessment case by case. Few animal models and assays have been validated for use in the nonclinical safety assessment of unexpected immunostimulation. The situation is worse regarding the prediction of hypersensitivity and autoimmune reactions. Our limited understanding of the molecular and cellular mechanisms of immunotoxicity accounts, at least partly, for this situation. Recent guidelines for the immunotoxicity safety assessment of drugs, even though conflicting on several points, will serve as an impetus not only to refine current animal models and assays, but also to search for better alternatives. The new data generated will have to be interpreted and extended to animal species other than just rodents. Likewise, animal results will have to be compared with findings in humans. The search for immunological endpoints that can be used in several animal species and in humans will therefore become essential. Specific endpoints and clinical criteria that can be included in clinical trials to further investigate the potential for immunotoxicity of new drugs will have to be defined. Because immunotoxicity plays a key role in drug-induced adverse effects, the role of immunotoxicology in drug safety assessment is indisputable and the systematic nonclinical as well as clinical immunotoxicity assessment of every new drug is deemed essential.

Clarithromycin-induced eosinophilic pneumonia

Clarithromycin (CAM) has been widely used for the treatment of respiratory infection. Macrolides are generally well tolerated and their adverse reactions are rare. An 80-year-old woman with nontuberculous mycobacterium infection was treated with combined chemotherapy, including isoniazid, rifampicin, and ethambutol. She developed a fever and peripheral blood eosinophilia, and new subpleural consolidations were observed on chest radiography three days after add-on therapy with CAM. The symptoms and clinical findings improved with the withdrawal of CAM. Histopathologic examinations confirmed the diagnosis of eosinophilic pneumonia. This is the first report of CAM-induced eosinophilic pneumonia.

From clinical to human toxicology: linking animal research and risk assessment in man

Since the 1960s, clinical toxicologists have primarily focused on acute poisonings. This proved very successful as the prognosis markedly improved with the use of resuscitation methods, evidence-based management and new antidotes. This latter area was the first major instance linking animal research and clinical toxicology, as illustrated with N-acetyl-cysteine or specific antibodies. Simultaneously the evolution of poison centers was a critical turning point as '2nd generation' centers are increasingly involved in risk assessment and toxicovigilance. Human toxicology is a broader area in that it is also involved in the toxicity evaluation of xenobiotics with the resulting need to link animal research and risk assessment to match the results of preclinical studies with clinical observations. However, this is not an easy task as experimental and clinical toxicologists seldom share ideas and expertise. Immunotoxicology is an example of this situation. Most of the available data on immunosuppression was obtained in animals and not in man, whereas allergic reactions have been extensively investigated in man, but overlooked in animals until recently. One of the major challenges facing toxicology is to bridge the gap between animal research and risk assessment in man. Human toxicology is expected to play a role in taking up this challenge.

Evidence for a T-lymphocyte dependent mechanism involving proinflammatory cytokines in anticonvulsant hypersensitivity syndrome: a case report

The anticonvulsant drug hypersensitivity syndrome (AHS) is a potentially fatal drug reaction associated with aromatic antiepileptic drugs, the pathogenic mechanisms of which are still unclear. We studied a 2-year-old female affected with AHS after phenobarbital treatment. In vitro experiments showed a T-lymphocyte response to the drug and an increased, dose-related, IL-6 production after drug incubation. These findings suggest that AHS may be caused by a T-lymphocyte dependent mechanism, involving pro-inflammatory cytokines.