Urticaria: The 1-1-1 Criterion for Optimized Risk Atratification in β-Lactam Allergy Delabeling

Evaluation of patients labeled with a penicillin allergy to promote antimicrobial stewardship in dental practice

BACKGROUND

Approximately 10% of the US population self-reports a penicillin allergy history or are labeled as penicillin allergic. However, from 90% through 99% of these patients are not allergic on formal evaluation.

CASE DESCRIPTION

Patients labeled as penicillin allergic receive broader-spectrum and sometimes less-effective antibiotics, thereby contributing to increased treatment failures, antibiotic resistance, and adverse drug reactions. Self-reported penicillin allergy can be eliminated or classified as low-, medium-, or high-risk after a careful review of patient history. This allows these patients to be delabeled; that is, having any reference to their penicillin allergy history or of having an allergy to penicillin eliminated from their health records.

PRACTICAL IMPLICATIONS

Oral health care professionals are ideally placed to partner in both antibiotic stewardship interventions by means of recognizing pervasive mislabeling and aiding in the process of delabeling.

Safe Penicillin Allergy Delabeling in Primary Care: A Systematic Review and Meta-Analysis

BACKGROUND

Ten percent of the population is labeled as allergic to penicillin(s), when in fact 90% of these labels are inappropriate. Recent studies have shown that inpatient delabeling by a direct drug challenge (dDC) is safe in low-risk patients. However, there is a need for outpatient and nonallergist delabeling.

OBJECTIVE

To assess the safety of delabeling low-risk adults by means of dDC in primary care.

METHODS

We searched the MEDLINE, Embase, and Cochrane Library databases from inception to March 15, 2022 (updated June 5, 2023) for studies performing dDC in adults in primary care or other outpatient settings. Two researchers independently screened studies for eligibility. The data extraction and critical appraisal were performed by 1 reviewer, and we pooled the results in a meta-analysis.

RESULTS

Of 2138 results, 12 studies (1070 participants) were eligible for inclusion. Three studies evaluated delabeling in primary care and 9 studies in an outpatient hospital setting. There were no critical adverse events during dDC. No reaction occurred in 97.13% of the 1070 patients, who previously labeled as penicillin-allergic, and were safely delabeled. Ten patients (<1%) developed an immediate reaction: 3 had self-limiting reactions and 7 needed antihistaminics, steroids, epinephrine, and/or salbutamol.

CONCLUSIONS

No serious allergic reactions are observed during direct amoxicillin challenge in adults in an outpatient setting. However, with the exception of 1 recent report, these studies are of low to moderate quality. Nonspecialist delabeling is promising, but further research is required on correct risk stratification and safety assessment in large cohort studies evaluating dDC in primary care.

Predicting Penicillin Allergy: A United States Multicenter Retrospective Study

BACKGROUND

Using the reaction history in logistic regression and machine learning (ML) models to predict penicillin allergy has been reported based on non-US data.

OBJECTIVE

We developed ML positive penicillin allergy testing prediction models from multisite US data.

METHODS

Retrospective data from 4 US-based hospitals were grouped into 4 datasets: enriched training (1:3 case-control matched cohort), enriched testing, nonenriched internal testing, and nonenriched external testing. ML algorithms were used for model development. We determined area under the curve (AUC) and applied the Shapley Additive exPlanations (SHAP) framework to interpret risk drivers.

RESULTS

Of 4777 patients (mean age 60 [standard deviation: 17] years; 68% women, 91% White, and 86% non-Hispanic) evaluated for penicillin allergy labels, 513 (11%) had positive penicillin allergy testing. Model input variables were frequently missing: immediate or delayed onset (71%), signs or symptoms (13%), and treatment (31%). The gradient-boosted model was the strongest model with an AUC of 0.67 (95% confidence interval [CI]: 0.57-0.77), which improved to 0.87 (95% CI: 0.73-1) when only cases with complete data were used. Top SHAP drivers for positive testing were reactions within the last year and reactions requiring medical attention; female sex and reaction of hives/urticaria were also positive drivers.

CONCLUSIONS

An ML prediction model for positive penicillin allergy skin testing using US-based retrospective data did not achieve performance strong enough for acceptance and adoption. The optimal ML prediction model for positive penicillin allergy testing was driven by time since reaction, seek medical attention, female sex, and hives/urticaria.

How to Define and Manage Low-Risk Drug Allergy Labels

Risk stratification in drug allergy implies that specific risk categories (eg, low, moderate, and high) classify historical drug hypersensitivity reactions. These risk categories can be based on reaction phenotypic characteristics, the timing of the reaction and evaluation, the required reaction management, and individual characteristics. Although a multitude of frameworks have been described in the literature, particularly for penicillin allergy labels, there has yet to be a global consensus, and approaches continue to vary between allergy centers. Immune-mediated drug allergies can sometimes be confirmed using skin testing, but a negative drug challenge is required to demonstrate tolerance and remove the allergy from the electronic health record ("delabel" the allergy). Even for quintessential IgE-mediated drug allergy, penicillin allergy, recent data reveal that a direct oral challenge, without prior skin testing, is an appropriate diagnostic strategy in those who are considered low-risk. Drug allergy pathogenesis and clinical manifestations may vary depending on the culprit drug, and as such, the optimal approach should be based on risk stratification that considers individual patient and reaction characteristics, the likely hypersensitivity reaction phenotype, the drug class, and the patient's clinical needs. This article will describe low-risk drug allergy labels, focusing on β-lactam and sulfonamide antibiotics, nonsteroidal anti-inflammatory drugs, iodinated contrast media, and common chemotherapeutics. This review will also address practical management approaches using currently available risk stratification and clinical decision tools.

Flow-based basophil activation test in immediate drug hypersensitivity. An EAACI task force position paper

Diagnosing immediate drug hypersensitivity reactions (IDHRs) can pose a significant challenge and there is an urgent need for safe and reliable tests. Evidence has emerged that the basophil activation test (BAT), an in vitro assay that mirrors the in vivo response, can be a complementary test for many drugs. In this position paper, members of Task Force (TF) "Basophil activation test in the evaluation of Drug Hypersensitivity Reactions" from the European Academy of Allergy and Clinical Immunology (EAACI) present the data from a survey about the use and utility of BAT in IDHRs in Europe. The survey results indicate that there is a great interest for using BAT especially for diagnosing IDHRs. However, there are still main needs, mainly in the standardization of the protocols. Subsequently consensus-based recommendations were formulated for: (i) Technical aspects of BAT in IDHRs including type of sample, management of drugs, flow cytometry protocols, interpretation of the results; and (ii) Drug-specific aspects that should be taken into account when performing BAT in relation to betalactams, neuromuscular blocking agents, fluoroquinolones, chlorhexidine, opioids, radio contrast media, chemotherapeutics, biological agents, nonsteroidal anti-inflammatory drugs, COVID vaccine, and excipients. Moreover, aspects in the evaluation of pediatric population have also been considered. All this indicates that BAT offers the clinician and laboratory a complementary tool for a safe diagnostic for IDHRs, although its place in the diagnostic algorithm depends on the drug class and patient population (phenotype, geography, and age). The standardization of BAT is important for generalizing this method beyond the individual laboratory.

Safety of Direct Drug Provocation for the Evaluation of Penicillin Allergy in Low-Risk Adults

BACKGROUND

About 10% of patients have a penicillin allergy label, but less than 5% of them are actually allergic. Unnecessary penicillin avoidance is associated with serious medical consequences. Given the growing number of these labels, it is imperative that our diagnostic strategy for penicillin allergy be as efficient as possible. The validity of traditionally used skin tests (STs) has been questioned, whereas drug provocation testing (DPT), the criterion standard, without previous ST appears very safe in most cases.

OBJECTIVE

To evaluate the safety of direct DPT without consideration for ST results and the validity of ST in the diagnosis of penicillin allergy.

METHODS

In this prospective cohort study without a control group, we recruited patients consulting an allergist for penicillin allergy. Patients underwent ST followed by DPT regardless of ST results. Patients with anaphylaxis to penicillin within the past 5 years or a severe delayed reaction were excluded, as were those with significant cardiorespiratory comorbidity.

RESULTS

None of the 1002 recruited patients had a serious reaction to DPT. Ten (1.0%) had a mild immediate reaction, of whom only 1 (0.1%) was considered likely IgE-mediated. The positive and negative predictive values of ST for an immediate reaction were 3.6% and 99.1%, respectively.

CONCLUSIONS

In a low-risk adult population reporting penicillin allergy, ST has very poor positive predictive value. Direct DPT without ST is safe and appears to be an ideal diagnostic strategy to remove penicillin allergy labels that could be implemented in first-line practice.

Penicillin allergy de-labelling by non-allergists: a comparison of testing protocols

Optimizing penicillin allergy de-labelling (PADL) to ensure patients with an incorrect penicillin allergy record are de-labelled with minimal patient harm is important for antibiotic stewardship. The heterogeneity of inclusion and exclusion criteria in the published penicillin allergy testing protocols risks suboptimal delivery of PADL. We compared the similarities and the differences between non-allergist-delivered PADL testing protocols and make suggestions for harmonization. The observed variation in testing practice has two broad elements: (i) definitions and terminology; and (ii) differences in the acceptability of perceived risk. All direct drug provocation testing (DDPT) protocols included patients with benign delayed rash as eligible for testing, although the remoteness of the rash, and the terminology used to describe the rash, differed. Patients with features of potential IgE reactions were excluded from most DDPT protocols, but not all of them. There was differing advice on how to manage patients who had subsequently tolerated penicillin since the index reaction and differences in which patients were considered ineligible for DDPT due to acuity of illness, comorbidities and concomitant medications. Standardization of the terminology used in penicillin allergy testing protocols and consensus on inclusion and exclusion criteria are required for safe and efficient PADL delivery at scale by non-allergists.

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.

A new pathway for penicillin delabeling in Norway

Background

Penicillin allergy is self-reported by 3-10% of patients admitted to hospital. The label is wrong in 90% of the cases and has severe health implications. Penicillin-delabeling can reverse the negative effects of the label, and pathways adapted to local practice are needed. No tools are available in Norway for penicillin delabeling outside an allergy clinic.

Objective

To create and validate the first penicillin delabeling pathway applicable outside an allergy clinic in Norway.

Methods

An interdisciplinary taskforce created a penicillin allergy delabeling program (PAD) adapted to the Norwegian health care system. This was validated in a prospective, single-center study. Very low-risk and low-risk patients underwent a direct oral penicillin challenge and high-risk patients were referred for allergologic evaluation.

Results

One-hundred forty-nine patients declaring penicillin allergy were included. Seventy-four (50%) were very-low- and low risk patients suitable for a direct oral penicillin challenge resulting in only 1 mild reaction. Sixty high-risk patients were eligible for an oral penicillin challenge after allergologic evaluation; 3 patients reacted non-severely.

Conclusion

We have created and demonstrated feasibility of the first penicillin delabeling program (PAD) applicable in a hospital setting outside an allergy clinic in Norway. Our data suggest this is safe and beneficial, with 49% patients delabeled through a direct oral penicillin challenge, performed without any serious adverse events, and an overall 87% delabeling rate.

Evaluating the PEN-FAST Clinical Decision-making Tool to Enhance Penicillin Allergy Delabeling

This cohort study evaluated the diagnostic accuracy of PEN-FAST as a clinical decision-making tool to enhance penicillin allergy evaluation.

The Quality and Management of Penicillin Allergy Labels in Pediatric Primary Care

BACKGROUND AND OBJECTIVES

Penicillin allergy labels are the most common drug allergy label. The objective of this study was to describe the quality and management of penicillin allergy labels in the pediatric primary care setting.

METHODS

Retrospective chart review of 500 of 18 015 children with penicillin allergy labels born from January 1, 2010 to June 30, 2020 randomly selected from an outpatient birth cohort from Texas Children's Pediatrics and Children's Hospital of Philadelphia networks. Penicillin allergy risk classification ("not allergy," "low risk," "moderate or high risk," "severe risk," "unable to classify") was determined based on documentation within (1) the allergy tab and (2) electronic healthcare notes. Outcomes of allergy referrals and penicillin re-exposure were noted.

RESULTS

Half of penicillin allergy labels were "unable to classify" based on allergy tab documentation. Risk classification agreement between allergy tabs and healthcare notes was fair (Cohen's ĸ = 0.35 ± 0.02). Primary care physicians referred 84 of 500 (16.8%) children to an allergist, but only 54 (10.8%) were seen in allergy clinic. All children who were challenged (25 of 25) passed skin testing. Removal of allergy labels was uncommon (69 of 500, 13.8%) but occurred more often following allergy appointments (26 of 54, 48%) than not (43 of 446, 9.6%, P < .001). Children delabeled by primary care physicians were as likely to tolerate subsequent penicillin-class antibiotics as those delabeled by an allergist (94% vs 93%, P = .87).

CONCLUSIONS

Penicillin allergy documentation within the allergy tab was uninformative, and children were infrequently referred to allergists. Future quality improvement studies should improve penicillin allergy documentation and expand access to allergy services.

The Combined Use of Chronological and Morphological Criteria in the Evaluation of Immediate Penicillin Reactions: Evidence From a Large Study

BACKGROUND

Immediate hypersensitivity reactions to penicillins are often labeled on the basis of a similar set of symptoms, but a key feature of these reactions that can be reproduced in diagnostic testing may be the timing of a reaction in relation to the dose administration.

OBJECTIVE

To determine whether the timing of a reaction in response to the last dose of a penicillin would predict the results of diagnostic testing.

METHODS

We evaluated 1074 patients by performing skin tests, serum specific IgE assays (ImmunoCAP), and challenges. Patients who were evaluated by us more than 6 months after their reactions and found negative were reevaluated within 2 to 4 weeks.

RESULTS

Patients who had reacted within 1 hour after the first dose, within 1 hour after subsequent doses, more than 1 hour to within 6 hours after the first dose, or more than 1 hour to within 6 hours after subsequent doses were classified as group A (758 individuals), B (92), C (67), or D (157), respectively. Penicillin hypersensitivity was diagnosed in 707 patients (65.8%) by skin tests (407 patients, 57.6%), ImmunoCAP (47, 6.6%), both tests (232, 32.8%), or challenges (21, 3%). A conversion to allergy-test positivity occurred in 7 of 10 patients with anaphylactic reactions and in 1 of 28 patients with other reactions who were reevaluated after negative challenges. The rate of penicillin-allergic patients in groups A, B, C, and D was 85%, 35.9%, 35.8%, and 3.8%, respectively. Only 1 of 107 patients reporting cutaneous reactions lasting more than 1 day had positive results to allergy tests.

CONCLUSIONS

IgE-mediated hypersensitivity can be diagnosed by skin tests in about 70% of subjects who react within 1 hour (eg, patients from groups A and B). This hypersensitivity can be lost over time, as demonstrated by the negativization of allergy tests in follow-up studies. In subjects with anaphylactic reactions, however, it is advisable to not consider this phenomenon definitive. In fact, a conversion to allergy test positivity can be observed in up to 20% of such subjects retested after negative challenges.

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.

Allergy Electronic Health Record Documentation: A 2022 Work Group Report of the AAAAI Adverse Reactions to Drugs, Biologicals, and Latex Committee

The allergy section of the electronic health record (EHR) is ideally reviewed and updated by health care workers during routine outpatient visits, emergency room visits, inpatient hospitalizations, and surgical procedures. This EHR section has the potential to help proactively and comprehensively avoid exposures to drugs, contact irritants, foods, and other agents for which, based on an individual's medical history and/or genetics, there is increased risk for adverse outcomes with future exposures. Because clinical decisions are made and clinical decision support is triggered based on allergy details from the EHR, the allergy module needs to provide meaningful, accurate, timely, and comprehensive allergy information. Although the allergy section of the EHR must meet these requirements to guide appropriate clinical decisions and treatment plans, current EHR allergy modules have not achieved this standard. We urge EHR vendors to collaborate with allergists to optimize and modernize allergy documentation. A work group within the Adverse Reactions to Drugs, Biologicals, and Latex Committee of the American Academy of Allergy, Asthma & Immunology was formed to create recommendations for allergy documentation in the EHR. Whereas it is recognized that the term "allergy" is often used incorrectly because most adverse drug reactions (ADRs) are not true immune-mediated hypersensitivity reactions, "allergy" in this article includes allergies and hypersensitivities as well as side effects and intolerances. Our primary objective is to provide guidance for the current state of allergy documentation in the EHR. This guidance includes clarification of the definition of specific ADR types, reconciliation of confirmed ADRs, and removal of disproved or erroneous ADRs. This document includes a proposal for the creation, education, and implementation of a drug allergy labeling system that may allow for more accurate EHR documentation for improved patient safety.

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.