Testing Strategies and Predictors for Evaluating Immediate and Delayed Reactions to Cephalosporins

Removing penicillin allergy label in a hospitalized adolescent with a remote penicillin and recent cephalosporin allergy

Background: β-Lactam antibiotics are widely used with increased utilization in hospitalized patients. Of this population, as high as 10-20% report an allergy to β-lactam antibiotics but <5% are at risk of developing clinically significant immunoglobulin E- or T-lymphocyte-mediated reactions. Most of the time, these reported allergies are present during an illness with no previous inquiry of their validity, which makes investigation and possible removal of this allergy label a challenge. Methods: We report a 16-year-old boy who presented with 1 week of night sweats, chills, headaches, and fatigue, followed by 1 day of fever and right knee swelling and who was diagnosed with septic bursitis. Due to concern of a penicillin allergy label, the patient was started on a cefepime infusion. Five minutes into the infusion, the patient reported puffy eyes and itchy throat, followed by a witnessed cascading flat nonpruritic erythematous rash from head to shoulders. This rash went away in 3 minutes after stopping the infusion and the patient being given 50 mg of intravenous diphenhydramine and 10 mg of oral dexamethasone. He was subsequently diagnosed with a cefepime allergy. Results: Allergy/immunology was the speciality consulted, and, by using a screening questionnaire, the patient's reported penicillin allergy was determined to be low risk. Subsequent 1-step oral challenge was the key to providing the patient with the necessary antibiotic course to resolve his infection. Conclusion: Multiple reported antibiotic allergies lead to poor antibiotic stewardship that causes impactful health and financial burden on the patient and health-care system. It is thus important to have an evidence-based systematic approach to de-label penicillin antibiotic allergy labels to reduce these potential harms.

Cefazolin as the mainstay for antibiotic prophylaxis in patients with a penicillin allergy in obstetrics and gynecology

Cefazolin is the most common antibiotic used for prophylaxis in obstetrics and gynecology. Among those with a penicillin allergy, alternative antibiotics are often chosen for prophylaxis, given fears of cross-reactivity between penicillin and cefazolin. Alternative antibiotics in this setting are associated with adverse sequelae, including surgical site infection, induction of bacterial resistance, higher costs to the healthcare system, and possible Clostridium difficile infection. Given the difference in R1 side chains between penicillin and cefazolin, cefazolin use is safe and should be recommended for patients with a penicillin allergy, including those who experience Immunoglobulin E-mediated reactions such as anaphylaxis. Cefazolin should only be avoided in those who experience a history of a severe, life-threatening delayed hypersensitivity reaction manifested as severe cutaneous adverse reactions (Steven-Johnson Syndrome), hepatitis, nephritis, serum sickness, and hemolytic anemia in response to penicillin administration. In addition, >90% of those with a documented penicillin allergy do not have true allergies on skin testing. Increased referral for penicillin allergy testing should be incorporated into routine obstetric care and preoperative assessment to reduce suboptimal antibiotic prophylaxis use. More education is needed among providers surrounding penicillin allergy assessment and cross-reactivity among penicillins and cephalosporins to optimize antibiotic prophylaxis in obstetrics and gynecology.

Penicillin Allergy Impact and Management

There is international evidence that penicillin allergies are associated with inferior prescribing and patient outcomes. A host of tools now exist from assessment (risk assessment tools, clinical decision rules) to delabeling (the removal of a beta-lactam allergy via testing or medical reconciliation) to reduce the impact of these "labels" in the hospital and community setting, as a primary antimicrobial stewardship intervention.

Direct challenges are the gold standard for most antibiotic allergy evaluations

Antibiotic allergies are frequently encountered in clinical practice, and delabeling of these allergies has individual and public health benefits. This review focuses on the evidence supporting graded challenges without preceding skin testing in adult and pediatric patients to the major groups of antibiotics including penicillins, cephalosporins, sulfamethoxazole, fluoroquinolones, tetracyclines, macrolides, metronidazole, carbapenems, and aztreonam. The cost savings, time savings, and evidence for performing graded challenges outside of an allergy/immunology office are also reviewed for graded challenges to penicillins.

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.

Improving antimicrobial stewardship with penicillin allergy testing: a review of current practices and unmet needs

Penicillin allergy, the most frequently reported drug allergy, has been associated with suboptimal antibiotic therapy, increased antimicrobial resistance, increased rates of Clostridioides difficile colonization and infection, as well as extended hospital length of stay and increased cost. Although up to 10% of all patients may report penicillin allergy, most penicillin allergies are not confirmed. As such, most patients with a penicillin allergy can still safely use penicillin and related drugs following a more precise assessment. Herein, we review the current practices and unmet needs in penicillin allergy testing. The diagnostic algorithm is mostly based on a clinical history assessment followed by in vivo testing, i.e. skin test and/or drug challenge. As these tests are labour and resource intensive, there is increased interest in point-of-care penicillin allergy de-labelling solutions incorporated into Antimicrobial Stewardship Programmes including digital assessment tools. These can be locally parameterized on the basis of characteristics of target populations, incidence of specific allergies and local antibiotic usage to perform clinical risk stratification. Safely ruling out any residual risk remains essential and in vivo drug challenge and/or skin testing should be systematically encouraged. Gradual understanding and convergence of the risk stratification of the clinical presentation of penicillin allergy is enabling a wider implementation of this essential aspect of antimicrobial stewardship through digitalized decision tools and in vivo testing. More research is needed to deliver point of care in vitro diagnostic tools to democratize this de-labelling practice, which would be highly beneficial to patient care. This progress, together with better education of patients and clinicians about the availability, efficacy and safety of penicillin allergy testing, will increase the dissemination of penicillin allergy assessment as an important component of Antimicrobial Stewardship Programmes.

Changes in Sensitization Patterns in the Last 25 Years in 619 Patients with Confirmed Diagnoses of Immediate Hypersensitivity Reactions to Beta-Lactams

Beta-lactam (BL) drugs are the antibiotics most prescribed worldwide due to their broad spectrum of action. They are also the most frequently implied in hypersensitivity reactions with a known specific immunological mechanism. Since the commercialization of benzylpenicillin, allergic reactions have been described; over the years, other new BL drugs provided alternative treatments to penicillin, and amoxicillin is now the most prescribed BL in Europe. Diagnosis of BL allergy is mainly based on skin tests and drug provocation tests, defining different sensitization patterns or phenotypes. In this study, we evaluated 619 patients with a confirmed diagnosis of BL-immediate allergy during the last 25 years, using the same diagnostic procedures with minor adaptations to the successive guidelines. The initial eliciting drug was benzylpenicillin, which changed to amoxicillin with or without clavulanic acid and cephalosporins in recent years. In skin tests, we found a decrease in sensitivity to major and minor penicillin determinants and an increase in sensitivity to amoxicillin and others; this might reflect that the changes in prescription could have influenced the sensitization patterns, thus increasing the incidence of specific reactions to side-chain selective reactions.

Understanding Penicillin Allergy, Cross-reactivity, and Antibiotic Selection in the Preoperative Setting

Penicillin allergies are reported by 8% to 15% of the US population, but up to 95% of these allergies do not correspond to a true allergy when tested. Recent studies have demonstrated that having a penicillin allergy label (PAL) results in a 50% increased odds of surgical site infection among patients reporting a penicillin allergy entirely attributable to the use of a beta-lactam alternative antibiotic (primarily clindamycin or vancomycin). This study provides a review of the prevalence of PAL, the cross-reactivity with cefazolin, immunogenic components of cefazolin and penicillin, and current guidelines for preoperative antibiotic selection in patients with PALs. On understanding these principles, a new set of guidelines and a risk stratification tool are proposed for assessing allergies and determining appropriate antibiotic choice, dosage, and timing in the orthopaedic preoperative setting.

Immediate and Delayed Hypersensitivity Reactions to Beta-Lactam Antibiotics

Beta-lactam antibiotics are the most commonly reported drug allergy in adults and children. More than 95% of those with reported allergy labels to beta lactams are not confirmed when subjected to allergy testing. Beta lactam antibiotics are associated with a wide spectrum of immediate and delayed drug hypersensitivity reactions. The latency period to symptoms and clinical presentation aids in the causality assessment. Risk stratification based on diagnosis and timing then allows for appropriate management and evaluation. Skin prick testing, intradermal testing and oral challenge are well established for evaluation of immediate reactions. Delayed intradermal testing, patch testing and oral challenge can also be considered for evaluation of mild to moderate delayed reactions. Cross-reactivity between beta-lactams appears to be driven most commonly by a shared R1 side-chain. Standardized algorithms, protocols and pathways are needed for widespread implementation of a pragmatic and effective approach to patients reporting beta lactam allergy.

Population-Based Incidence of New Ampicillin, Cephalexin, Cefaclor, and Sulfonamide Antibiotic "Allergies" in Exposed Individuals with and without Preexisting Ampicillin, Cephalexin, or Cefaclor "Allergies"

BACKGROUND

There is a theoretical concern, unconfirmed by population-based challenge data, that clinically significant, immunologically mediated hypersensitivity occurs among β-lactams sharing side chains.

OBJECTIVE

To determine the population-based allergy incidence associated with the use of β-lactams sharing exact R1 side chains (ampicillin, cephalexin, and cefaclor [ACC]), with or without a current ACC allergy or a sulfonamide antibiotic allergy for comparison.

METHODS

All courses of ACC and trimethoprim-sulfamethoxazole used by any Kaiser Permanente California members in 2017 and 2018, with follow-up through January 2019, were identified along with their preexisting antibiotic allergy status and all new antibiotic-specific allergies reported within 30 days of course initiation.

RESULTS

A total of 1,167,713 courses of ACC were administered to individuals. No sulfonamide antibiotic or ACC allergy and 4771 new ACC allergies (0.41%) were reported. Moreover, 130,032 courses of ACC were administered to individuals with a sulfonamide antibiotic allergy; no ACC allergy and 904 new ACC allergies (0.70%) were reported. There were 5,958 courses of ACC administered to individuals with an ACC allergy; 2,341 who also had sulfonamide antibiotic allergy, as well as 52 new ACC allergies (0.87%) were reported.

CONCLUSIONS

The incidence of new ACC allergy reports is minimally and no-specifically increased when a preexisting ACC or sulfonamide antibiotic allergy exists greater than the baseline incidence in the population. This argues against clinically significant, immunologically mediated cross-reactivity among β-lactams sharing exact side chains in individuals with preexisting but unconfirmed β-lactam allergy. Any previously reported, even unrelated antibiotic allergy appears to be a risk factor for reporting a new antibiotic allergy.

Classifying cephalosporins: from generation to cross-reactivity

PURPOSE OF REVIEW

To review the most recent literature studying the classifications, immunochemistry, and crossreactivity of allergy reactions to cephalosporins.

RECENT FINDINGS

Over the last five years, research interest has focused on three areas related to cephalosporin allergy: cross-reactivity among cephalosporins and with other beta-lactams; the incidence of adverse reactions in penicillin allergy patients or in reported penicillin allergy labels; and new cephalosporins structures involved in the immunological recognition.

SUMMARY

Meta-analysis of a substantial number of studies shows that cephalosporins are safer than previously thought. Evidence supports two main conclusions in that regard. First, there is a relatively low percentage of cross-reactivity between cephalosporins and other beta-lactams with penicillins in penicillin allergy patients. Second, there is a very low incidence of allergy reactions in nonselected as well as in selected penicillin allergy patients when cephalosporins are used prior to surgical intervention.On the other hand, few structures have been discovered related to the immune mechanism of cephalosporin allergy reactions, and these are far from being ready to use in clinical practice.

Hidden Dangers: Recognizing Excipients as Potential Causes of Drug and Vaccine Hypersensitivity Reactions

Excipients are necessary as a support to the active ingredients in drugs, vaccines, and other products, and they contribute to their stability, preservation, pharmacokinetics, bioavailability, appearance, and acceptability. For both drugs and vaccines, these are rare reactions; however, for vaccines, they are the primary cause of immediate hypersensitivity. Suspicion for these "hidden dangers" should be high, in particular, when anaphylaxis has occurred in association with multiple chemically distinct drugs. Common excipients implicated include gelatin, carboxymethylcellulose, polyethylene glycols, and products related to polyethylene glycols in immediate hypersensitivity reactions and propylene glycol in delayed hypersensitivity reactions. Complete evaluation of a suspected excipient reaction requires detailed information from the product monograph and package insert to identify all ingredients that are present and to understand the function and structure for these chemicals. This knowledge helps develop a management plan that may include allergy testing to identify the implicated component and to give patients detailed information for future avoidance of relevant foods, drugs, and vaccines. Excipient reactions should be particularly considered for specific classes of drugs where they have been commonly found to be the culprit (eg, corticosteroids, injectable hormones, immunotherapies, monoclonal antibodies, and vaccines). We provide a review of the evidence-based literature outlining epidemiology and mechanisms of excipient reactions and provide strategies for heightened recognition and allergy testing.