The revolving door: antibiotic allergy labelling in a tertiary care centre

Penicillin or cephalosporin antibiotic allergy label: Influence on length of stay and hospital readmission

Background

A penicillin or cephalosporin antibiotic (PCA) allergy label (PCAAL) has negative implications for both the patient and health care alike.

Objective

A retrospective study was undertaken to evaluate the influence of a PCAAL on length of stay (LOS) and hospital readmissions.

Methods

Over 4 weeks, inpatients with a PCAAL who were referred to the allergy service or opportunistically reviewed were grouped in the categories delabeled (group 1a) or advice not followed (ie, label carriage) (group 1b). Comparator groups without a PCAAL were identified, those either on a PCA (the PCA group [group 2]) or on a non-PCA (the non-PCA group [group 3]).

Results

The study population comprised 77 patients as follows: group 1a (n = 19), group 1b (n = 6), group 2 (n = 36), and group 3 (n = 16). Those in group 1a were significantly older (median age 78 years) than those in group 1b (median age 53 years [P = .013]) or group 3 (median age 59 years [P = .013]).There was a trend toward lower LOS in group 1a (10 days) than in group 1b (11.5 days [P = not significant]). Group 2 had a significantly lower LOS (6 days) than either both group 1a (10 days [P = .043]) or group 3 (15 days [P = .002]). Group 3 had the highest rate of patients readmitted within 30 days (n = 5 [71.4%]).

Conclusion

A PCAAL carries influence on both LOS and readmissions, thus identifying the prompt need for allergy review to provide specific recommendations: delabeling and transition to an appropriate antibiotic. The significantly older group of those with a PCAAL who received a PCA after delabeling (ie, a 20-year age difference) may also be a signal that more elderly and comorbid patients benefit from this intervention the most.

Beta-lactam allergy in patients: an antibiotic stewardship challenge

BACKGROUND

Patients are commonly reported as being allergic to beta-lactam (BL) antibiotics. However, many patients with this reported allergy are able to receive BL treatments because they do not have true allergies. In many cases these are simply intolerances due to side effects reported as an allergy. Delabelling these patients leads to better clinical outcomes, optimal antibiotic usage, decreased bacterial resistance and reduced healthcare costs. Therefore, the aims of this study were to identify incorrectly labelled BL allergies in hospitalised patients and to assess antibiotic use in delabelled patients in order to establish a quality indicator to optimise antimicrobial treatments.

METHODS

A prospective study was conducted in which hospitalised patients treated with antimicrobial drugs and labelled as 'BL-allergic' were identified by clinical pharmacists. An allergist assessed whether patients were suitable candidates for a skin test or oral challenge. The Allergy Service removed 'BL-allergic' labels if negative results were obtained. Delabelled patients were followed up by clinical pharmacists to study the use of BL antibiotics as a result of the delabelling programme.

RESULTS

A total of 176 suspected allergic patients were identified and 91 (51.7%) were tested either by a skin test or oral challenge based on the patient indicators. Seven (16.4%) patients tested were allergic to BL antibiotics, 76 (83.5%) were totally delabelled and eight (0.1%) were partially delabelled. Thirty-two (38.1%) delabelled patients required antibiotic treatment in another inpatient or outpatient setting, of whom 27 (84.3%) patients with a new infectious episode received BL treatments while five (15.7%) continued to receive antimicrobial treatments without BL.

CONCLUSION

After the implementation of a protocol to detect incorrect BL allergy labels, 83.5% of the patients in this cohort were completely delabelled. This shows that there is a clear opportunity to optimise the use of antibiotics by delabelling 'BL-allergic' patients.

The Burden of Self-Reported Antibiotic Allergies in Health Care and How to Address It: A Systematic Review of the Evidence

BACKGROUND

Antibiotics are the first-line treatment for bacterial infections; however, overuse and inappropriate prescribing have made antibiotics less effective with increased antimicrobial resistance. Unconfirmed reported antibiotic allergy labels create a significant barrier to optimal antimicrobial stewardship in health care, with clinical and economic implications.

OBJECTIVE

A systematic review was conducted to summarize the impact of patient-reported antibiotic allergy on clinical outcomes and various strategies that have been employed to effectively assess and remove these allergy labels, improving patient care.

METHODS

The review was undertaken using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A critical appraisal was conducted on all studies and a narrative synthesis was performed to identify themes.

RESULTS

Four themes emerged: the prevalence of antibiotic allergy, impact of antibiotic allergy on antimicrobial prescribing, impact of antibiotic allergy on clinical outcomes, and delabeling strategies to improve clinical outcomes. Of the 32 studies, including 1,089,675 participants, the prevalence of reported antibiotic allergy was between 5% and 35%. Patients with a reported antibiotic allergy had poorer concordance with prescribing guidelines in 30% to 60% of cases, with a higher use of alternatives such as quinolone, tetracycline, macrolide, lincosamide, and carbapenem and lower use of beta-lactam antibiotics. Antibiotic allergy delabeling was identified as an intervention and recommendation to advance the state of the science.

CONCLUSIONS

There is substantial evidence within the literature that antibiotic allergy labels significantly impact patient clinical outcomes and a consensus that systematic assessment of reported antibiotic allergies, commonly referred to as delabeling, improves the clinical management of patients.

Characterizing Antibiotic Allergy Labels in a Large UK Hospital Population to Inform Antimicrobial Stewardship and Delabeling Assessment Strategy

BACKGROUND

Antibiotic allergy labels are important barriers to treatment and antimicrobial stewardship, but their prevalence in UK hospitals is poorly described.

OBJECTIVE

To ascertain the prevalence and characteristics of antibiotic allergy labels in a large UK hospital setting and estimate the proportion of penicillin allergy labels for which point-of-care (POC) delabeling assessment would be appropriate.

METHODS

Electronic health records data were analyzed from all patients treated at Cambridge University Hospitals NHS Foundation Trust in 2019. Validated POC delabeling risk stratification criteria were retrospectively applied to penicillin allergy labels.

RESULTS

Recorded reactions to antibiotics were present in 11.8% of all patients (32,148 of 273,216), 16.3% of inpatients (13,874 of 85,230), and 9.7% of outpatients (18,274 of 187,986). Penicillins were the commonest reaction precipitant described (9.0% of patients; 24,646 of 273,216), followed by sulfonamides/trimethoprim (1.4%; 3869 of 273,216) and macrolides/lincosamides (1.3%; 3644 of 273,216). A total of 3.9% of inpatients had recorded reactions to >1 antibiotic class (3348 of 85,230). Cutaneous manifestations were the most commonly described reaction features (40.7% of labels; 15,821 of 38,902). Of 15,949 labels describing probable or possible penicillin "allergy" with sufficient detail to allow for the retrospective assessment of POC delabeling suitability, 1702 were deemed suitable for removal or downgrading of the label to "intolerance" without further investigation (10.7%), 11,887 were appropriate for POC assessment using an oral penicillin challenge (OPC) or OPC with prior bedside skin testing (74.5%), and 2360 were identified as unsuitable for any form of POC assessment (14.8%).

CONCLUSIONS

Antibiotic allergy labels are highly prevalent in a UK hospital setting. A large proportion of penicillin allergy labels may be suitable for POC delabeling assessment.

Evaluating the cost-effectiveness of testing pregnant women for penicillin allergy

INTRODUCTION

True penicillin allergy is rare and is commonly incorrectly reported. In fact, less than five percent of patients who report a penicillin allergy will have a currently active clinically-significant IgE- or T-cell-mediated hypersensitivity when appropriately tested. Penicillin is the agent of choice for intrapartum antibiotic prophylaxis to reduce the risk of group B streptococcus early-onset disease in the newborn. Inaccurate penicillin allergy status may lead to inappropriate antibiotic use, as most alternative drugs are more expensive and broader spectrum than penicillin. Penicillin allergy testing has been found to be safe in pregnancy and cost-effective in other patient populations.

OBJECTIVE

To evaluate the cost-effectiveness of penicillin allergy testing and appropriate antibiotic treatment (test then treat strategy) compared to usual care among pregnant women.

METHODS

We developed a decision tree to evaluate the cost of providing appropriate care via a test then treat strategy for pregnant women who report a penicillin allergy, compared to usual care.

RESULTS

Using the test then treat strategy the additional cost to ensure appropriate care for all pregnant women who report a penicillin allergy, was $1122.38 per person. Adopting a test then treat strategy increased the number of appropriate antibiotic use from 7,843/10,000 to 10,000/10,000 simulations.

CONCLUSION

Our results show that a test then treat strategy for pregnant women who report a penicillin allergy is a good-value intervention.

History-based preoperative evaluation of antibiotic-related allergies and design of an easy to use questionnaire

BACKGROUND

An unconfirmed history of antibiotic allergies may negatively influence prescribing patterns for preoperative antibiotic prophylaxis and increase rates of postoperative wound infections through unnecessary use of alternative antibiotics.

METHODS

After a literature search, we developed a questionnaire for the structured collection of antibiotic allergy history in the anesthesia consultation center and tested it over 2 years at a tertiary care hospital under everyday conditions as part of a quality assurance project. All data were evaluated completely anonymously in the context of standard care.

RESULTS

After refining the questionnaire, we analyzed 4866 recorded optimized questionnaires, of which 51 were incomplete. An antibiotic allergy was denied 4312 times and affirmed 503 times, which corresponds to 10% in our sample. The most frequent single substances or groups in the 503 respondents with a positive history of antibiotic allergy were penicillin in 271 (54%), amoxicillin in 65 (13%), an unknown single agent in 50 (10%) and multiple substances in 25 (5%). The reported event occurred more than 10 years ago in 192 (38%) of the respondents, less than 10 years ago in 116 (23%), and 195 (39%) could not provide information. The time from exposure to symptom onset was less than 1h in 96 (19%), between 1 and 24 h in 75 (15%), more than 24 h in 106 (21%), and the remainder could not provide information. Allergy-specific treatment was recalled by 75 (15%) respondents, 287 (57%) reported not having received specific treatment, and the remainder could not recall. A specific allergy test was reported by 55 (11%) respondents, 337 (67%) said no allergy test had been made, and the rest could not recall. A substance-specific allergy passport was issued in 80 (16%) respondents. According to expert assessment, symptoms compatible with an IgE-mediated reaction were present in 96 (19%) of the respondents. An IgE-mediated reaction was considered possible in 70 (14%) and could be excluded by history in 337 (67%) of respondents. Out of 503 respondents with a positive history 51 (10%) could not remember the allergic substance but 7 (14%) of the 51 reported symptoms compatible with severe anaphylaxis or anaphylactic shock and 6 of the 51(12%) reported symptoms possibly related to an IgE-mediated reaction.

DISCUSSION

Our survey revealed approximately 10% of respondents reporting an antibiotic allergy, which is in the upper range of data published in international literature and corresponds most closely to American data. Thus, the topic is also relevant to German anesthesia consultation centers, given the high rate of respondents who could have been "delabeled" based on the comprehensive assessment of their history. More expert allergy testing is needed in patients who report symptoms related or probably related to an IgE-mediated reaction. In our opinion, a special issue exists in those patients who did not remember the exact antibiotic but reported symptoms compatible with severe anaphylaxis putting them at high risk of unintended re-exposure.

Differences in beta-lactam and penicillin allergy: Beyond the West and focusing on Asia-Pacific

Beta-lactam (BL) antibiotic "allergy" labels are common, but often overdiagnosed. Although much research has been focused on the BL allergy and the delabelling process in the West, studies from other parts of the world remain sparse. This review outlines the contrasting global epidemiology, shifting clinical practices and disparities of BL allergy in the Asia-Pacific region compared with the West. Innovative strategies to overcome barriers in BL allergy workup are discussed and potential directions for future research and service development are also proposed.

Penicillin allergy SHACK: Survey of hospital and community knowledge

AIM

Penicillin allergy accounts for the majority of all reported adverse drug reactions in adults and children. Foregoing first-line antibiotic therapy due to penicillin allergy label is associated with an increased prevalence of infections by resistant organisms and longer hospitalisation. Clinician awareness of allergy assessment, referral indications, management of allergy and anaphylaxis is therefore vital but globally lacking. We aim to assess the knowledge of penicillin allergy, assessment and management in Western Australian health professionals.

METHODS

An anonymous survey was distributed to pharmacists, nurses and physicians within Western Australian paediatric and adult Hospitals, Community and General Practice.

RESULTS

In total, 487/611 were completed and included in the statistical analysis. Only 62% (301/487) of respondents routinely assessed for patient medication allergies. Of those who assessed allergy, 9% (28/301) of respondents met the Australian standards for allergy assessment. Only 22% (106/487) of participants correctly cited all indications for management with adrenaline in anaphylaxis to antibiotics and 67% (197/292) of physicians rarely or never referred to an allergy service. Paediatric clinicians had an increased understanding of allergy assessment and anaphylaxis management. Recent penicillin allergy education within a 5-year period led to significant improvements in allergy knowledge.

CONCLUSION

Overall, knowledge, assessment and management of penicillin allergies among practitioners in Western Australia are currently inadequate in adults and paediatric clinicians to provide safe and effective clinical care. The implementation of a targeted education program for WA health professionals is urgently required and is expected to improve clinician knowledge and aid standardised penicillin assessment (de-labelling) practices.

Standardized testing and written communication improve patient understanding of beta-lactam allergy testing outcomes: A multicenter, prospective study

Background

Historical penicillin allergy is commonly reported, but the lack of standardized allergy clinic practices may diminish the ability to delabel beta-lactam allergy appropriately.

Objective

We sought to improve beta-lactam allergy testing and patient understanding of their antibiotic allergy status by standardizing testing and communication practices between 7 adult and pediatric hospital centers.

Methods

Phase 1 prospectively described the beta-lactam allergy testing practices at each center. Following this, practice was standardized to achieve a defined panel of skin testing reagents, pro forma result letters for patients and referring doctors, and provision of medical alert jewelry to those with confirmed allergy. Testing outcomes and patient perception regarding allergy status 8 weeks postassessment were compared before (phase 1) and after standardization (phase 2). Primary outcomes were the percentage of participants delabeled after testing, and concordance rates between participant perception of their allergy status and their status as determined by the treating physician at 8-week follow-up.

Results

Of 195 adult and pediatric participants (median age, 50 years; 21.5% <18 years; 36.9% males), 75% were delabeled of their beta-lactam allergy. No patient experienced anaphylaxis related to any beta-lactam delabeling testing. In phase 1, 75% of participants received written results, 52% were informed verbally, and 48% received results in more than 1 form. All phase 2 participants received written results (P < .01), 61% received verbal results from a physician as well (P > .05). At 8-week follow-up, 54% of phase 1 participants had concordant perceptions of their allergy status as the testing team versus 91.6% in phase2 (P < .001). Of the 17 participants who were delabeled and treated with a beta-lactam antibiotic during the 8-week follow-up period, there were no reported allergic reactions, although 1 participant experienced anaphylaxis following exposure to amoxicillin-clavulanic acid 1 year after delabeling.

Conclusions

Standardization of testing and written patient information improved short-term patient perception of beta-lactam allergy status.

Improving routine prenatal penicillin allergy testing for reported penicillin allergy

Background

Patients with self-reported antibiotic allergies have a higher cost of care, more frequent infections with resistant bacteria and worse health outcomes than patients without antibiotic allergies. Ultimately, less than 5% of patients who report a penicillin allergy have a clinically significant immune-mediated hypersensitivity reaction when tested. As 10%–30% of the population of pregnant patients are colonised for group B Streptococcus (GBS) and guidelines recommend penicillin as the treatment of choice for GBS, current recommendations support penicillin allergy testing in pregnant patients who report an allergy.

Methods and intervention

In this quality improvement project, nursing staff used an algorithm outlining inclusion and exclusion criteria to determine which patients were eligible to have penicillin allergy testing completed. Penicillin allergy testing consisted of a skin test using benzylpenicilloyl polylysine (Pre-Pen), penicillin G potassium, amoxicillin and alkaline hydrolysis mix (penicilloate) as a prick skin test, followed by intradermal skin test and finally an oral challenge with either amoxicillin or penicillin. Patient outcomes were analysed to evaluate the impact of the intervention.

Results

Of the 1266 patients receiving prenatal care during the intervention, 236 (19%) reported a history of penicillin allergy, and 212 if these were eligible for testing. 150 of the eligible patients were offered penicillin allergy testing. 101 patients (67%) completed testing and 49 (33%) declined testing. Seven patients (7%) had positive penicillin allergy testing, while 94 patients (93%) had negative penicillin allergy testing and were immediately de-labelled as penicillin allergic. Seventeen of the de-labelled patients subsequently tested positive for GBS colonisation, and all received intrapartum penicillin without adverse events.

Conclusions

Pursuing penicillin allergy testing for pregnant patients with reported penicillin allergy is a safe and feasible approach, allowing for allergy de-labelling and safe, guideline-driven antimicrobial therapy during subsequent labour and delivery hospitalisations. Cost-effectiveness of the allergy testing and impact on later episodes of care should be further investigated.

Association of antibiotic allergy labels with hospital length of stay

BACKGROUND

Many antibiotic allergy labels (AAL) are invalid. Excluding true allergy in people with AAL ("delabeling") could improve health outcomes and decrease costs. Several studies with limited covariate adjustment have associated AAL with a prolonged hospital length of stay (LOS).

OBJECTIVE

This study determined whether AAL's association with LOS persisted after extensive adjustment for potential confounders and covariates.

METHODS

All nonpsychiatric admissions to a tertiary care teaching hospital from 2012 to 2015 were included. Generalized estimating equation methods were used to model the daily discharge likelihood as a function of AAL and other important factors (death risk score, daily discharge score, daily severity of illness score, antibiotic use, hospital day and location, weekend-holiday status, and service).

RESULTS

A total of 111,611 admissions (76,460 patients) were studied, in which 16,489 (14.8%) had recorded AAL. Patients with an AAL had a notably greater disease burden: they were older and had more comorbidities, greater health system utilization, and higher death risk. In the univariate analysis, AAL was associated with a significantly decreased daily discharge likelihood (odds ratio [OR], 0.93; [95% confidence interval, 0.90-0.95]). After adjustment for potential confounders and covariates, AAL was not associated with daily discharge likelihood (adjusted OR [aOR] without antibiotics: 1.00 [0.98-1.03]; aOR with antibiotics: 1.02 [0.99-1.04]). Similar results were also seen with penicillin AAL (aOR without antibiotics: 0.99 [0.95-1.02]; aOR with antibiotics: 1.00 [0.96-1.03]).

CONCLUSION

Antibiotic allergy label was strongly associated with a greater disease burden. After adjusting for important covariates, our analysis found no significant association between AAL and hospital LOS.

Assessment of the validity of the beta-lactam antibiotic allergy assessment tool for use in the rural context, QLD

OBJECTIVE(S)

The objective of the study was to validate a clinical aid to guide the assessment and management of a patient's listed beta-lactam antibiotic allergy for use in rural areas of Australia.

DESIGN

Rural generalists, pharmacists and junior doctors completed an online assessment of eight patient case studies using the tool.

SETTING

The study was conducted in the Southern Downs, QLD.

PARTICIPANTS

Twenty-seven rural generalists, nine pharmacists and eight junior doctors.

MAIN OUTCOME MEASURES

The sensitivity of the selected allergy phenotype and management option for each case study was calculated by profession and overall. Hazardous responses were reported by management category and profession.

RESULTS

The sensitivity overall for phenotype selection was 82.4% (95% CI, 78.0-86.2) and for management 88.1% (95% CI, 84.2-91.2). The sensitivity for phenotype selection was lower for junior doctors than other professions 73.4% (95% CI, 60.9-83.7), but did not reach statistical significance (p = 0.08). A total of 10/308 responses for management recommended the least restrictive option of direct delabelling or oral challenge, where the correct answer was skin prick testing or referral to an allergist.

CONCLUSION(S)

With further education the tool could be a key component of increased antimicrobial stewardship in rural areas in Australia.

Burden of antibiotic allergy labels in Australian aged care residents: Findings from a national point-prevalence survey

OBJECTIVE

To determine the prevalence of antibiotic allergy labels (AALs) in Australian aged care residents and to describe the impact of labels on antibiotic prescribing practices.

DESIGN

Point-prevalence survey.

SETTING

Australian residential aged care facilities.

PARTICIPANTS

We surveyed 1,489 residents in 407 aged care facilities.

METHODS

Standardized data were collected on a single day between June 1 and August 31, 2018, for residents prescribed an antibiotic. An AAL was reported if it was documented in the resident's health record. Resident-level data were used to calculate overall prevalence, and antibiotic-level data were used to report relative frequency of AALs for individual antibiotics and classes.

RESULTS

Among 1,489 residents, 356 (24%) had 1 or more documented AALs. The AALs for penicillin (28.3%), amoxicillin or amoxicillin/clavulanic acid (10.5%), cefalexin (7.2%), and trimethoprim (7.0%) were most commonly reported. The presence of an AAL was associated with significantly less prescribing of penicillins (OR, 0.43; 95% CI, 0.31-0.62; P < .001) and significantly more prescribing of lincosamides (OR, 4.81; P < .001), macrolides (OR, 2.03; P = .007), and tetracyclines (OR, 1.54; P = .033). Of residents with AALs, 7 residents (1.9%) were prescribed an antibiotic that was listed on the allergy section of their health record.

CONCLUSIONS

A high prevalence of AALs was observed among residents of Australian aged care facilities, comparable to the prevalence of AALs in high-risk hospitalized patients. Significant increases in prescribing of lincosamide, macrolide, and tetracycline agents poses a potential risk to aged populations, and future studies must evaluate the benefits of AAL delabelling programs tailored for aged care settings.

Role of clinical history in beta-lactam hypersensitivity

PURPOSE OF REVIEW

Understand how the clinical history has been used to risk stratify patients reporting a beta-lactam allergy, both in clinical care pathways and predictive models.

RECENT FINDINGS

Drug allergy clinical care pathways have emerged as a safe and effective method of stratifying patients with a reported beta-lactam allergy into risk categories, with 'low-risk' patients able to proceed straight to direct challenges or test doses. These methods have streamlined antibiotic stewardship policies and penicillin allergy de-labeling. However, how to define 'low-risk' has been subject to much debate. New research has developed predictive models that utilize the clinical history to assess a patient's true risk of beta-lactam allergy.

SUMMARY

The clinical history has long been an essential part of drug allergy evaluation and has proven invaluable within the past decade in the development of drug allergy clinical pathways. Evidence-based predictive models that use the clinical history to assess a patient's true risk of beta-lactam allergy offer tremendous promise, but differ in crucial areas such as the populations they study, the predictor variables they use, and the ultimate accuracy they attain. These models highlight key aspects of the drug allergy history and pave the way for future large-scale research.

DALES, Drug Allergy Labels in Elective Surgical patients: a prospective multicentre cross-sectional study of incidence, risks, and attitudes in penicillin de-labelling strategies

BACKGROUND

We sought to define the prevalence and nature of patient-reported drug allergies, determine their impact on prescribing, and explore drug allergy knowledge and attitudes amongst anaesthetists.

METHODS

We performed a prospective cross-sectional study in 213 UK hospitals in 2018. Elective surgical patients were interviewed, with a detailed allergy history taken in those self-reporting drug allergy. Anaesthetists completed a questionnaire concerning perioperative drug allergy.

RESULTS

Of 21 219 patients included, 6214 (29.3 %) (95% confidence interval [CI]: 28.7-29.9) reported drug allergy. Antibiotics, NSAIDs, and opioids were the most frequently implicated agents. Of a total of 8755 reactions, 2462 (28.1%) (95% CI: 29.2-31.1) were categorised as high risk for representing genuine allergy after risk stratification. A history suggestive of chronic spontaneous urticaria significantly increased the risk of reporting drug allergy (odds ratio 2.68; 95% CI: 2.4-3; P<0.01). Of 4756 anaesthetists completing the questionnaire, 1473 (31%) (95% CI: 29.7-32.3) routinely discuss perioperative allergy risk with patients. Prescribing habits in the presence of drug allergy labels differ depending on the implicated agent. Most anaesthetists (4678/4697; 99.6%) (95% CI: 99.4-99.8) prescribe opioids when reactions are consistent with side-effects, although 2269/4697 (48%) (95% CI: 46.9-49.7) would avoid the specific opioid reported.

CONCLUSIONS

Almost 30% of UK elective surgical patients report a history of drug allergies, but the majority of reported reactions are likely to be non-allergic reactions. Allergy labels can impact on perioperative prescribing through avoidance of important drugs and use of less effective alternatives. We highlight important knowledge gaps about drug allergy amongst anaesthetists, and the need for improved education around allergy.

Prevalence of drug allergy in South Australia

INTRODUCTION

Drug allergy is commonly reported in patient notes and electronic health records. The prevalence of self-reported drug allergy in the general Australian population has not previously been studied.

METHODS

We surveyed a representative sample of the South Australian adult population regarding their own perception of drug allergy, including drug type and severity as well as the use of medical alert devices. Data were weighted to correspond to age and sex of the South Australian population.

RESULTS

22.2% of adults in South Australia consider themselves allergic to one or more drugs, 9.3% declared themselves to be allergic to penicillin, 5% to an antibiotic other than penicillin, and 13% to one or more antibiotics. Drug allergy and penicillin allergy was significantly more prevalent in females, and increased with age. Thirteen percent of those with an antibiotic allergy reported a severe reaction, of whom 27% wore a medical notification device. Of those allergic to penicillin, 75% had their index reaction more than 10 years ago and did not report severe features.

DISCUSSION

Self-reported drug allergy is common in the general population, as it is in medical clinic and hospital populations. The majority of those reporting penicillin allergy would be considered low-risk and suitable for delabelling procedures. This article is protected by copyright. All rights reserved.

Penicillin Allergy Testing Is Cost-Saving: An Economic Evaluation Study

BACKGROUND

Having a penicillin allergy label is associated with the use of less appropriate and more expensive antibiotics and increased healthcare utilization. Penicillin allergy testing results in delabeling most allergy claimants and may be cost-saving. This study aimed to project whether penicillin allergy testing in patients reporting a penicillin allergy is cost-saving.

METHODS

In this economic evaluation study, we built decision models to project the economic impact of 2 strategies for a patient with a penicillin allergy label: (1) perform diagnostic testing (drug challenges, with or without skin tests); and (2) do not perform diagnostic testing. The health service perspective was adopted, considering costs with penicillin allergy tests, and with hospital bed-days/outpatient visits, antibiotic use, and diagnostic testing. Twenty-four base case decision models were built, accounting for differences in the diagnostic workup, setting (inpatient vs outpatient) and geographic region. Uncertainty was explored via probabilistic sensitivity analyses.

RESULTS

Penicillin allergy testing was cost-saving in all decision models built. For models assessing the performance of both skin tests and drug challenges, allergy testing resulted in average savings (in United States [US] dollars) of $657 for inpatients (US: $1444; Europe: $489) and $2746 for outpatients (US: $256; Europe: $6045). 75% of simulations obtained through probabilistic sensitivity analysis identified testing as the less costly option.

CONCLUSIONS

Penicillin allergy testing was projected to be cost-saving across different scenarios. These results are devised to inform guidelines, supporting the adoption of policies promoting widespread testing of patients with a penicillin allergy label.

Safety and efficacy of direct two-step penicillin challenges with an inpatient pharmacist-driven allergy evaluation

Background: Penicillin allergy is commonly reported and has clinical and financial consequences for patients and hospitals. A penicillin evaluation program can safely delabel patients and optimize antibiotic therapy. Pharmacists who perform this task have focused on a detailed interview or penicillin skin testing (PST). Antibiotic graded challenge after PST requires more resources and is more costly than going directly to a two-step challenge. Objective: To determine whether a pharmacist-driven penicillin allergy evaluation and a testing protocol that primarily uses direct oral challenges can safely delabel patients. Methods: Adult patients (ages >18 years) with a penicillin allergy in their electronic medical record (EMR) who were admitted between September 2019 and June 2020 were eligible. Although all patients with penicillin allergy were eligible, priority was given to patients who required antibiotics. Patients were interviewed, and, if indicated, based on an institutional protocol, were tested by using PST and/or two-step oral challenge. If the patient passed the challenge, then the penicillin allergy label was removed in the EMR and the patient counseled. Demographic information, allergy questionnaire results, testing results, and changes in antimicrobial therapy were collected. Results: Fifty patients were evaluated from September 2019 to June 2020. Ninety-six percent of the patients were delabeled, and antibiotic therapy changed for 54%. Twenty patients were delabeled with an interview alone, and 30 patients underwent oral two-step challenge. Only one patient required PST. Conclusion: A pharmacist-driven penicillin allergy evaluation program focused on direct oral graded challenges and bypassing PST can effectively delabel admitted patients. However, more safety data are needed before implementation of similar programs to optimize antibiotic treatment.

Prevalence of Antibiotic Allergy Labels in a Tertiary Referral Center in Belgium

BACKGROUND

Antibiotic (AB) allergies are among the most frequently occurring adverse drug reactions. In US literature, AB allergy labels (AAL) are reported in 10% to 15% of patients' charts; however, large-scale European analyses are scarce.

OBJECTIVES

To retrospectively assess the prevalence of AAL in a tertiary referral hospital in Belgium between 2010 and 2018.

METHODS

Patients who consulted and/or were hospitalized during the study period, who had been labeled with an AB allergy, were selected for further analysis.

RESULTS

Of 1,009,598 unique patients (outpatients, n = 736,469; inpatients, n = 273,129), 28,147 patients (3%) were registered with 1 or more AAL, being 1% of outpatients (n = 9562) and 7% of inpatients (n = 18,585). Women were more likely to carry an AAL (68%) compared with men (32%, P < .001). In patients with an AAL, 9% had multiple labels and 5% had labels for multiple AB classes. Most frequently, beta-lactams were involved (84% of AAL), followed by quinolones (7%) and sulfonamides and macrolides (both 3%). Moreover, 88% of the reactions were self-reported, mostly being an unspecified rash (53%), whereas only 3% were considered confirmed AAL.

CONCLUSION

With an overall prevalence of 3%, the burden of AAL is less in our Western European center compared with US reports. However, this prevalence most likely still represents an overestimation of genuine AB allergic patients because most labels lack confirmation and/or specifications. Our work indicates that knowledge of the local epidemiology of AAL is necessary to estimate the impact of better allergy labeling and delabeling strategies.

The impact of antibiotic allergy labels on antibiotic exposure, clinical outcomes, and healthcare costs: A systematic review

OBJECTIVE

A growing body of evidence suggests that antibiotic allergy labels as documented in medical records are a risk factor for poor clinical outcomes. In this systematic review, we aimed to determine how antibiotic allergy labels influence 3 domains: antibiotic use and exposure, clinical outcomes, and healthcare-related costs.

DESIGN

We performed a systematic review to identify studies reporting outcomes in patients with antibiotic allergy labels compared to nonallergic counterparts. The search included PubMed, EMBASE, Cochrane CENTRAL, EBSCO, Cochrane Database of Abstracts of Reviews of Effects and Web of Science. Two reviewers independently screened studies for inclusion and abstracted data. Studies were graded using the Newcastle-Ottawa quality assessment scale. Study outcomes included antibiotic use, clinical outcomes, and economic outcomes.

RESULTS

In total, 41 studies met our criteria for inclusion. These studies varied in medical specialty, patient population, healthcare delivery system, and design, but most were conducted among adults age >18 years (85%) in the inpatient setting (82.5%). Among 34 studies examining antibiotic exposure, 32 (94%) found that patients with antibiotic allergy labels received more broad-spectrum antibiotics. Moreover, 31 studies examined clinical outcomes such as length of hospitalization, ICU admission, hospital readmission, multidrug-resistant or opportunistic infection, or mortality, and 27 (87%) found that allergy-labeled patients had at least 1 negative outcome. Of 9 studies examining healthcare costs, 7 (78%) found that allergy-labeled patients incurred significantly higher drug or hospital-related costs.

CONCLUSIONS

Antibiotic allergy labels have negative effects on antibiotic use, clinical outcomes, and economic outcomes in a variety of clinical settings and populations.

Antibiotic allergy labels and optimal antimicrobial stewardship

BACKGROUND

Although common, antimicrobial allergy labels (AAL) rarely reflect immunologically-mediated hypersensitivity and can lead to poorer outcomes from alternative antimicrobial agents. Antimicrobial stewardship programs are ideally placed to assess AAL early as a means of improving antimicrobial use.

OBJECTIVES

To quantify the prevalence of AAL in patients referred for antimicrobial stewardship review and assess their impact on antibiotic prescribing, patient mortality, hospital length of stay, readmission, and rates of multidrug-resistant infections.

METHODS

We conducted a retrospective analysis of adult patients referred for inpatient antimicrobial prospective audit and feedback rounds (PAFR) via an electronic referral system (eReferrals) over a 12-month period in 2015. Outcome data was collected for a period of 36 months following the initial review.

RESULTS

Of the 639 patient records reviewed, 630 met inclusion criteria; 103 (16%) had an AAL, of which 82 (13%) had reported allergies to β-lactam antibiotics. Those with AAL were significantly less likely to be receiving guideline-recommended antimicrobial therapy (50% versus 64%, p=0.0311), however there were no significant difference in mortality, hospital length of stay, readmission or increased incidence of multidrug-resistant infections.

CONCLUSIONS

Our cohort demonstrated that AAL was associated with reduced adherence to antibiotic guidelines. The lack of association with adverse outcomes may reflect limitations within the study including retrospective cohort study numbers and observational nature, further skewed by high rates of poor documentation. A clear opportunity exists for antimicrobial stewardship programs to incorporate allergy assessment, delabelling, challenge and referral into these rounds. This article is protected by copyright. All rights reserved.

The democratization of de-labeling: a review of direct oral challenge in adults with low-risk penicillin allergy

INTRODUCTION

Penicillin antibiotic allergy labels (AALs) are common and lead to significant negative health and health system outcomes. Direct oral challenge offers a rapid and cost-effective way of removing inaccurate AALs and improving outcomes.

AREAS COVERED

A narrative review (Medline, May 2020) of direct oral challenge in low-risk penicillin allergy in adults is described, and the evidence for the safety and efficacy of this approach in inpatients, outpatients, and special patient groups is presented.

EXPERT OPINION

Whilst the current literature demonstrates the safety and efficacy of direct oral challenge in de-labeling low-risk penicillin allergy in adults, novel approaches are needed to improve access to antibiotic allergy assessment and address the growing global need.

Immediate cephalosporin allergy

BACKGROUND

Patients who suffer from acute IgE-mediated allergy to a cephalosporin antibiotic are frequently assumed to be at high risk of allergy to other cephalosporins and penicillins.

AIM

To define cross-reactivity patterns in patients with confirmed allergy to a cephalosporin.

METHODS

Subjects presenting with a history of immediate allergy to a cephalosporin-family antibiotic between March 2009 and July 2017 were investigated with specific IgE testing to penicillin, amoxycillin and cefaclor, followed by skin prick testing, intradermal testing and drug provocation testing with a panel of penicillins and cephalosporins.

RESULTS

Out of 564 subjects with a reported beta-lactam allergy, 90 identified a cephalosporin as their index drug. Fifty-five (61.1%) of the 90 subjects tested had a history consistent with an IgE-mediated reaction, of whom 24 (43.6%) were proven to be allergic to their index cephalosporin. Twenty (83.3%) of the 24 were allergic only to their index cephalosporin. Of the four remaining subjects, two were co-sensitised to another beta-lactam with a similar side chain, while the other two had no specific cross-reactivity pattern. Major and minor penicillin determinants were negative for all cephalosporin-allergic individuals.

CONCLUSION

In our cohort, cephalosporin allergy does not appear to be a class effect, with most cases found allergic only to their index cephalosporin. Co-sensitisation to other cephalosporins or penicillins was uncommon, and when it occurred, was usually consistent with side chain cross-reactivity.

Penicillin allergy: a practical approach to assessment and prescribing

Penicillin allergies are not always lifelong. Approximately 50% are lost over five years

A reaction to penicillin during a childhood infection is unlikely to be a true allergy

Only 1–2% of patients with a confirmed penicillin allergy have an allergy to cephalosporins. In patients with a low risk of severe allergic reactions, cephalosporins are a relatively safe treatment option

Patients with a history of delayed non-severe reactions, such as mild childhood rashes that occurred over 10 years ago, may be suitable for an oral rechallenge with low-dose penicillin. This should be done in a supervised hospital environment

In many cases, with appropriate assessment and allergy testing, it may be possible to remove the penicillin allergy label

An update on allergy and anaphylaxis in pediatric anesthesia

Childhood allergy is common, and increasing. Many children are incorrectly labeled as having allergy or adverse drug reactions. This can pose a dilemma for anesthetists and lead to a change in practice or drug selection. We review the pathophysiology of hypersensitivity reactions and the implications for anesthesia of food allergy, atopy, and family history of allergy in children. The epidemiology of anaphylaxis is discussed. We discuss the common triggers of perioperative anaphylaxis in children and explore emerging triggers including chlorhexidine and sugammadex. Accurate data on pediatric perioperative anaphylaxis is limited worldwide, with marked geographic variation. This highlights the need for accurate local, district and/or nationwide incident reporting. The clinical features, diagnosis, and management of anaphylaxis under anesthesia are discussed. We review the process of expert allergy testing following a suspected case of anaphylaxis to guide future safe anesthesia administration. The preoperative consultation is an opportunity for referral for allergy testing to allow de-labeling. This has the potential for improved antibiotic stewardship and more effective treatment with first-line therapeutic agents.

Safety of direct drug provocation testing in adults with penicillin allergy and association with health and economic benefits

BACKGROUND

Nonprescription of penicillin-containing antibiotics in patients diagnosed with penicillin allergy is associated with morbidity and mortality. Adverse reactions to penicillins comprise type A and B reactions.

OBJECTIVE

To assess the feasibility of penicillin allergy evaluation without penicillin skin testing (PST) for adult patients with type B reactions and the health and economic benefits of this process.

METHODS

Inpatients at an Australian tertiary hospital between April 1, 2017, and April 30, 2018, with a diagnosis of type B penicillin allergy, requiring a penicillin-containing antibiotic for treatment, were included. All patients underwent clinical history review, PST, and drug provocation testing (DPT).

RESULTS

Seventy-one patients were enrolled. Sixty-three reported a history of type B or unknown adverse reactions. No patients had a history of anaphylaxis requiring intubation or epinephrine within the last 10 years or a history suggesting Gell and Coombs type 2, 3, or 4 (severe) hypersensitivity reaction. Seven did not complete DPT because the treating team used a β-lactam antibiotic other than amoxicillin. Fifty-four of 56 remaining patients (96%) completed 3-day DPT to amoxicillin with no adverse reaction. Two experienced mild cutaneous reactions. Penicillin allergy evaluation was significantly associated with reduced length of stay, reduced hospital expenditure on bed and second-line antibiotics, and reduced readmission rates.

CONCLUSION

Penicillin allergy evaluation with DPT without PST may be feasible for all adult patients with a reported history of type B reactions to penicillins who do not have a history of anaphylaxis within the last 10 years or a type 2, 3, or 4 (severe) hypersensitivity reaction.

Focus group study exploring the issues and the solutions to incorrect penicillin allergy-labelled patients: an antibiotic stewardship patient safety initiative

OBJECTIVES

Approximately 10% of the general population are reported to have a penicillin allergy, but more than 90% of these patients are able to tolerate penicillins after formal assessment. Patients with penicillin allergy labels have poorer health outcomes and incorrect labels impact negatively on healthcare systems. Identifying patients with incorrect penicillin allergy labels (those who can safely take penicillin) has the potential to benefit patients and healthcare systems. This study explores barriers and enablers towards identifying and removing incorrect penicillin allergy labels in inpatients ('delabelling').

METHODS

Two focus groups were completed with a total of 17 doctors, nurses and pharmacists at a 750-bed district general hospital in England.

RESULTS

Thematic analysis identified four main themes: managing penicillin allergic patients, environmental barriers, education for patients and staff and a future delabelling process. Staff reported that identifying and delabelling incorrect penicillin allergy records was a complex task and not a priority during the acute presentation. Participants felt confident removing erroneous allergy records if the patient was able to describe the reaction. Balancing time to confirm and delabel with competing duties was felt to be a challenge. Revisiting the discussion with the patient when time was less pressured was offered as a solution to the problem. The lack of provision to translate uncertainty about allergy status in the electronic health record was mentioned as a barrier to accurate documentation of allergy history. Ensuring all patient records were amended to reflect the new allergy status was identified as a challenge. A delabelling process involving nurses, doctors and pharmacist was discussed.

CONCLUSIONS

Delabelling patients with erroneous penicillin allergy labels was recognised as a complex problem. A patient pathway involving nurses, doctors and pharmacist is likely to be the optimal method to safely delabel patients.

Adverse drug reaction classification by health professionals: appropriate discrimination between allergy and intolerance?

Background

The correct classification of an adverse drug reaction (ADR) as allergy (immunological) or intolerance (non-immunological) has important clinical implications. The aim of this study was to examine the ability of health professionals to discriminate between allergy and intolerance, classify the severity of the ADR and degree of contraindication.

Methods

Health professionals were presented ten ‘real-life’ ADR scenarios using an online questionnaire and asked to: categorise the reaction as allergy or intolerance, rate the severity of the reaction and judge the level of contraindication of the causative drug. The number and proportion of responses were calculated for each of the cases presented and associations between classification of reaction type, severity and level of contraindication were examined.

Results

A total of 394 responses were received. Overall 59.0% (SD 28.9) correctly categorised the cases, 60.8% (SD 16.8) classified the severity correct, and less than half (44.7%, SD 28.6) correctly identified the level of contraindication. The proportion of health professionals correctly answering the type, severity and level of contraindication for the allergy case was significantly higher (p < 0.0001) by comparison to the intolerance cases (type: 56.6% ± 33.1; severity: 57.3 ± 11.9; level of contraindication: 38.5 ± 19.9).

Conclusions

Health professionals have suboptimal understanding of classification of ADRs. Strategies are required to strictly avoid re-exposure of patients to drugs which carry an increased risk of inducing a dangerous reaction, whilst minimising the avoidance of drugs which are of minimal risk or allowing the use of low-risk drugs where the benefits may be significant.

Management of a surgical patient with a label of penicillin allergy: narrative review and consensus recommendations

Unsubstantiated penicillin-allergy labels are common in surgical patients, and can lead to significant harm through avoidance of best first-line prophylaxis of surgical site infections and increased infection with resistant bacterial strains. Up to 98% of penicillin-allergy labels are incorrect when tested. Because of the scarcity of trained allergists in all healthcare systems, only a minority of surgical patients have the opportunity to undergo testing and de-labelling before surgery. Testing pathways can be modified and shortened in selected patients. A variety of healthcare professionals can, with appropriate training and in collaboration with allergists, provide testing for selected patients. We review how patients might be assessed, the appropriate testing strategies that can be used, and the minimum standards of safe testing.

Allergy alerts - The incidence of parentally reported allergies in children presenting for general anesthesia

BACKGROUND AND AIM

Pediatric patients increasingly report allergies, including allergies to food and medications. We sought to determine the incidence and, nature of parent-reported allergies in children presenting for surgery and its significance for anesthetists.

METHODS

We prospectively collected data on admissions through our surgical admission unit over a 2-month period at a pediatric tertiary care teaching hospital. Data collected included patient demographics, history of atopy, with more comprehensive information collected if an allergy was reported. A clinical immunologist and an anesthetist reviewed the documentation of all patients reporting an allergy.

RESULTS

We reviewed 1001 pediatric patients, 158 (15.8%) patients with parent-reported allergies; to medications/drugs (n = 73), food (n = 66), environmental allergens (dust/grasses, n = 35), tapes/dressings (n = 27), latex (n = 4), and venom (eg, bee, wasp, n = 9). Forty-one patients reported antibiotic allergies, with Beta-lactam antibiotics being the most common, with the majority presenting with rash alone (57%). Ten patients reported allergies to nonsteroidal anti-inflammatory drugs and eight to opioids. Twenty-four patients reported egg and/or peanut allergy. Only 3/1001 (0.3%) patients were deemed to have evidence of likely IgE-mediated drug allergy. Of the reported allergies, only 60 (38.2%) had been investigated prior, most likely to be followed up were food (53%) and environmental allergies (44.4%). Only 4/73 (5.5%) reported medication allergies had further follow-up. Just four patients (0.4% of the entire cohort) had drug sensitivities/allergies that were likely to majorly alter anesthesia practice.

CONCLUSION

Only the minority of parent-reported allergies in pediatric surgical patients were specialist confirmed and likely to be clinically relevant. Self-reported food allergy is commonly specialist verified whereas reactions to medications were generally not. Over-reporting of allergies is increasingly common and limits clinician choice of medications. Better education of patients and their families and more timely verification or dismissal of parent-reported reactions is urgently needed.

Antibiotic allergy labels in hospitalized and critically ill adults: A review of current impacts of inaccurate labelling

Antibiotic allergy labels (AALs) are reported by approximately 20% of hospitalized patients, yet over 85% will be negative on formal allergy testing. Hospitalized patients with an AAL have inferior patient outcomes, increased colonization with multidrug-resistant organisms and frequently receive inappropriate antimicrobials. Hospitalized populations have been well studied but, to date, the impact of AALs on patients with critical illness remains less well defined. We review the prevalence and impact of AALs on hospitalized patients, including those in in critical care.

Penicillin allergy de-labelling ahead of elective surgery: feasibility and barriers

BACKGROUND

Around 10-15% of the in-patient population carry unsubstantiated 'penicillin allergy' labels, the majority incorrect when tested. These labels are associated with harm from use of broad-spectrum non-penicillin antibiotics. Current testing guidelines incorporate both skin and challenge tests; this is prohibitively expensive and time-consuming to deliver on a large scale. We aimed to establish the feasibility of a rapid access de-labelling pathway for surgical patients, using direct oral challenge.

METHODS

'Penicillin allergic' patients, recruited from a surgical pre-assessment clinic, were risk-stratified using a screening questionnaire. Patients at low risk of true, immunoglobulin E (IgE)-mediated allergy were offered direct oral challenge using incremental amoxicillin to a total dose of 500 mg. A 3-day course was completed at home. De-labelled patients were followed up to determine antibiotic use in surgery, and attitudes towards de-labelling were explored.

RESULTS

Of 219 patients screened, 74 were eligible for inclusion and offered testing. We subsequently tested 56 patients; 55 were de-labelled. None had a serious reaction to the supervised challenge, or thereafter. On follow-up, 17 of 19 patients received appropriate antimicrobial prophylaxis during surgery. Only three of 33 de-labelled patients would have been happy for the label to be removed without prior specialist testing.

CONCLUSION

Rapid access de-labelling, using direct oral challenge in appropriately risk-stratified patients, can be incorporated into the existing surgical care pathway. This provides immediate and potential long-term benefit for patients. Interest in testing is high among patients, and clinicians appear to follow clinic recommendations. Patients are unlikely to accept removal of their allergy label on the basis of history alone.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: AN17/92982.

Antibiotic allergy labels-the impact of taking a clinical history

BACKGROUND

Many patients admitted to hospital have an antibiotic allergy (AAL) documented in their medical record. In many of these, the reaction is not a hypersensitivity reaction or may no longer be relevant. Despite this, the label adversely affects patient care directly in terms of antibiotic selection, and indirectly in terms of patient costs and the development of antimicrobial resistance.

AIMS

To estimate the prevalence of AALs in a cohort of hospitalised patients, to investigate the feasibility of de-labelling through re-challenge based solely upon clinical grounds.

DESIGN

This is a cross-sectional study conducted over a 6-month period on adult inpatients. An allergy history was taken from each patient and compared with medical record data regarding allergy. Antibiotic selection data were collected (if relevant). It was then determined whether immediate de-labelling was appropriate, if direct provocation test (DPT) could be relatively safely performed, and if antibiotic selection was appropriate.

RESULTS

Three thousand eight hundred and fifty five patients were screened, 553 (14.35%) had an AAL, and 352 were interviewed. There were 426 AALs; 276 (64.8%) towards a penicillin. After taking a detailed clinical history of the type of reaction, approximately 20% could be immediately de-labelled and educated (non-allergic, non-severe reactions) and another 38% with either a definite or vague history of mild cutaneous reaction would be suitable for an attempt at clinical de-labelling DPT.

CONCLUSIONS

These simple measures to 'de-label' patients appropriately, would increase the quality of care of this group known to have higher costs, infection with more resistant bacteria and worse health outcomes that 'non-labelled' patients.

The Cost of Self-Reported Penicillin Allergy: A Systematic Review

BACKGROUND

Patients who report a penicillin (PCN) allergy receive suboptimal antibiotic therapy compared with patients not reporting an allergy. However, a majority of patients who report PCN allergy are not truly allergic on confirmatory testing. Ruling out PCN allergy by testing may improve clinical and economic outcomes for patients with reported allergies requiring antibiotic therapy.

OBJECTIVE

The objective of this study was to summarize clinical and economic outcomes associated with PCN allergy and provide recommendations for future cost-effectiveness analyses for PCN allergy testing.

METHODS

A literature search was conducted using SCOPUS, EMBASE, and PubMed, including all articles published any date through April 25, 2017 (PROSPERO Registration number 42017064112). A total of 1518 abstracts were found during the initial search with 96 duplicates, for a total of 1422 articles for screening. Thirty articles were included for qualitative synthesis and full data extraction.

RESULTS

The majority of the studies included had an observational design focusing on inpatient admissions. The most frequently measured outcome in the context of PCN allergy was optimizing antibiotic therapy. Patients with PCN allergy were found to have direct drug costs during inpatient admission ranging from no difference to an additional $609/patient compared with patients without PCN allergy. Outpatient prescription costs were estimated from $14 to $193/patient higher for PCN allergic patients. Total inpatient costs were less for patients without PCN allergy with average savings from $1145 to $4254/patient.

CONCLUSIONS

Evaluations of clinical and economic outcomes of PCN allergy are primarily observational and focus on inpatient populations. Long-term relationships between PCN allergy and clinical and economic outcomes are unknown.

Typical antimicrobials induce mast cell degranulation and anaphylactoid reactions via MRGPRX2 and its murine homologue MRGPRB2

Mast cells are unique immune cells that function as sentinels in host defence reactions, including immediate hypersensitivity responses and allergic responses. The mast cell-specific receptor named MAS-related G protein-coupled receptor X2 (MRGPRX2) triggers mast-cell degranulation, a key process in anaphylactoid reactions. It is widely observed that antimicrobials can induce pseudo-allergic reactions (i.e. IgE-independent mechanism) with symptoms ranging from skin inflammation to life-threatening systemic anaphylaxis. However, their direct involvement and the mechanisms underlying anaphylactoid reactions caused by antimicrobials have not been demonstrated. Structurally different antimicrobials were screened by Ca²⁺ imaging using MRGPRX2 overexpressing HEK293 cells. MRGPRX2 related anaphylactoid reactions induced by these components were investigated by body temperature drop and mast cell degranulation assays. We showed that MRGPRX2 is involved in allergic-like reactions to three types of antimicrobials in a dose-dependent manner. However, mast cells lacking the receptor show reduced degranulation. Furthermore, mice without MAS-related G protein-coupled receptor B2 (the orthologous gene of MRGPRX2) exhibited reduced substance-induced inflammation. Interestingly, β-lactam and antiviral nucleoside analogues did not induce anaphylactic reactions, which were also observed in vitro. These results should alarm many clinicians that such drugs might induce anaphylactoid reactions and provide guidance on safe dosage of these drugs.