BSACI guideline for the set-up of penicillin allergy de-labelling services by non-allergists working in a hospital setting

Covalent penicillin-protein conjugates elicit anti-drug antibodies that are clonally and functionally restricted

Many archetypal and emerging classes of small-molecule therapeutics form covalent protein adducts. In vivo, both the resulting conjugates and their off-target side-conjugates have the potential to elicit antibodies, with implications for allergy and drug sequestration. Although β-lactam antibiotics are a drug class long associated with these immunological phenomena, the molecular underpinnings of off-target drug-protein conjugation and consequent drug-specific immune responses remain incomplete. Here, using the classical β-lactam penicillin G (PenG), we probe the B and T cell determinants of drug-specific IgG responses to such conjugates in mice. Deep B cell clonotyping reveals a dominant murine clonal antibody class encompassing phylogenetically-related IGHV1, IGHV5 and IGHV10 subgroup gene segments. Protein NMR and x-ray structural analyses reveal that these drive structurally convergent binding modes in adduct-specific antibody clones. Their common primary recognition mechanisms of the penicillin side-chain moiety (phenylacetamide in PenG)-regardless of CDRH3 length-limits cross-reactivity against other β-lactam antibiotics. This immunogenetics-guided discovery of the limited binding solutions available to antibodies against side products of an archetypal covalent inhibitor now suggests future potential strategies for the 'germline-guided reverse engineering' of such drugs away from unwanted immune responses.

Penicillin Allergy in China: Consequences of Inappropriate Skin Testing Practices and Policies

Penicillins are the most frequently prescribed class of medications worldwide and first-line antibiotic of choice for most bacterial infections. They are also commonly labelled as the culprit of drug 'allergy'; leading to obligatory use of second-line antibiotics, suboptimal antibiotic therapy and increased antimicrobial resistance. However, the majority of reported penicillin 'allergy' labels are found to be incorrect after allergy testing, emphasising the importance of proper drug allergy testing and evaluation. Penicillin skin testing (PST) remains an important component of drug allergy diagnosis; however, its practice and policies significantly differ across the world. Inappropriate and non-evidence-based PST practices can lead to consequences associated with allergy mislabelling. Even within different regions of China, with a population exceeding 1.4 billion, there are marked differences in the implementation, execution and interpretation of PST. This review aims to examine the differences in PST between Mainland China, Hong Kong and the rest of the world. We critically analyse the current practice of 'pre-emptive' PST in Mainland China, which has a significant false-positive rate leading to high levels of penicillin allergy mislabelling. Non-evidence-based practices further compound the high false-positive rates of indiscriminatory PST. We postulate that inappropriate PST policies and practices may exacerbate the mislabelling of penicillin allergy, leading to unnecessary overuse of inappropriate second-line antibiotics, increasing antimicrobial resistance and healthcare costs. We advocate for the importance of more collaborative research to improve the contemporary workflow of penicillin allergy diagnosis, reduce mislabelling and promote the dissemination of evidence-based methods for allergy diagnosis.

β-Lactam allergy delabeling is safe and saves costs in Primary Care

OBJECTIVE

To determine whether the β-lactam allergy delabeling was safe and cost-saving in Primary Care (PC) patients.

DESIGN

We have conducted a retrospective chart review of PC patients with β-lactam allergy label evaluated in our Allergy Unit between 2017 and 2022. SITE: Allergy Department. Hospital Virgen del Rocio (Sevilla).

PARTICIPANTS

A total of 391 patients labeled for β-lactam allergy in PC were studied.

MAIN MEASUREMENTS

(a) Outcome evaluation of a β-lactam allergy delabeling procedure. (b) A ratio between the total e-prescribed antibiotic cost and the number of treatment days (the experimental daily antibiotic cost or EDAC) before and after delabeling was analyzed in delabeled and truly allergic patients.

RESULTS

The results of skin testing were positive in 9.2% of the reported cases (36 of 391 patients). The reactions to oral provocation challenge (OPC) occurred in 2.14% of the patients who underwent negative skin testing to offending β-lactam (in 15 of 699 OPC). A total of 307 patients (78.5%) were delabeled; 70 (17.9%) had a β-lactam selective response and 14 (3.59%) reacted to both penicillin and cephalosporin. The EDAC before and after the procedure in delabeled patients was significantly lower (0.88 € vs 0.62 €, p<10-3), than that observed in truly allergic group (0.87 € vs. 0.76 €, p=not significant).

CONCLUSION

To delabel β-lactam allergy in Primary Care patients is safe in most patients, cost-saving in antibioticotherapy, and allows identify the main clinical β-lactam allergy phenotypes that benefit from this procedure.

Performance Characteristics of Basophil Activation Tests for Diagnosing Penicillin Allergy: A Meta-Analysis

BACKGROUND

Approximately 10% of the global population identify themselves as penicillin allergic, yet 90% are not truly allergic and could safely tolerate penicillin. There is no simple way to identify these people. Current in vitro diagnostics include specific immunoglobulin E (with a sensitivity of 19% and specificity of 97%) and a basophil activation test (BAT) with undefined sensitivity and specificity.

OBJECTIVE

To define the sensitivity and specificity of BAT in the diagnosis of penicillin allergy METHODS: We searched PubMed and EMBASE from inception to April 2, 2023, for original studies evaluating the performance characteristics of BAT for penicillin allergy in adults. Study selection, data extraction, risk of bias, assessment with QUADAS-2 tool, certainty assessment with Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology were performed independently, in duplicate. Meta-analysis was performed using Reitsma methodology.

RESULTS

Twenty-two studies fulfilled the inclusion criteria. Twelve used the same positive threshold giving a summary point sensitivity 51% (95% confidence interval [95% CI]46%-56%) and specificity 89% (95% CI 85%-93%). Significant risk of bias was identified owing to patient selection. GRADE certainty of evidence rated sensitivity very low due to imprecision and specificity as low. There was great heterogeneity in methods used. Use of 1,000 basophils per test did not improve performance above 500 basophils.

CONCLUSIONS

BAT sensitivity is highly variable across studies and remains too low to be considered as a routine element of clinical practice. BAT specificity is not as good as specific immunoglobulin E in penicillin allergy diagnosis. Significant further work is required in this field before clinical application of BAT in routine practice.

A multicentre observational study to investigate feasibility of a direct oral penicillin challenge in de-labelling 'low risk' patients with penicillin allergy by non-allergy healthcare professionals (SPACE study): Implications for healthcare systems

OBJECTIVE

The huge burden of inaccurate penicillin allergy labels (PALs) is an important driver of antimicrobial resistance. This is magnified by insufficient allergy specialists and lack of 'point-of-care' tests. We investigated the feasibility of non-allergy healthcare professionals (HCPs) delivering direct oral penicillin challenges (DPCs) for penicillin allergy de-labelling.

METHODS

This prospective observational study was conducted in three hospitals in England across three settings (acute medical, pre-surgical and haematology-oncology). Patients with a PAL were screened and stratified as low risk/high risk. Low risk patients (non-immune mediated symptoms, benign rash, tolerated amoxicillin since and family history) underwent a DPC.

RESULTS

N = 2257 PALs were screened, 1054 were eligible; 643 were approached, 373 declined, 270 consented and 259 risk stratified (low risk = 155; high risk = 104). One hundred and twenty-six low risk patients underwent DPC, 122 (96.8%) were de-labelled with no serious allergic reactions. Conversion rate from screening-to-consent was 12% [3.3% and 17.9% in acute and elective settings respectively; odds ratios for consent were 3.42 (p < 0.001) and 5.53 (p < 0.001) in haematology-oncology and pre-surgical setting respectively. Common reasons for failure to progress in the study included difficulty in reaching patients, clinical instability/medical reasons, lacking capacity to consent and psychological factors.

INTERPRETATION

DPCs can be delivered by non-allergy HCPs. A high proportion of patients with PALs did not progress in the study pathway. Strategies to deliver DPC at optimal points of the care pathway are needed to enhance uptake. Elective settings offer greater opportunities than acute settings for DPC. The safety and simplicity of DPCs lends itself to adoption by healthcare systems beyond the UK, including in resource-limited settings.

Outpatient and primary care direct provocation challenges for antibiotic allergy in children

OBJECTIVE

To evaluate the use of a questionnaire-based decision-making algorithm to triage children with reported antibiotic allergies to proceed directly to an oral provocation challenge.

DESIGN

Cohort study.

SETTING

Children aged 2-16 years attending paediatric emergency department over 1 year (1 June 2018 till 31 May 2019) or identified from four primary care centres in Sheffield with a recorded antibiotic allergy and no previous testing.

PARTICIPANTS

313 children with 325 recorded antibiotic allergies.

EXPOSURE

Clinical decision-making algorithm used to either exclude, directly delabel or stratify children to oral antibiotic challenge in outpatient department or primary care practice.

MAIN OUTCOME MEASURES

To assess the safety of using the questionnaire-based algorithm for proceeding to a direct oral provocation challenge.The secondary outcomes were to look for associations and predictive factors in positive challenges and to assess parent/carer acceptability of the service by using Likert Scale.

RESULTS

Successful contact was made with 200 children, of which 153 children could be evaluated based on inclusion criteria, engagement and availability of medical records.15 children were directly delabelled based on history and records. 138 children underwent challenges in outpatient and primary care. 6% of challenges were reactive with a mild, delayed reaction. Overall, a delabelling rate of 91% was achieved. There were no clear predictors for a positive challenge.

CONCLUSION

Our questionnaire-based algorithm for stratifying children with antibiotic allergies to proceed directly to an oral outpatient or primary care challenge was found to be safe, feasible and acceptable.

Non-allergist healthcare workers views on delivering a penicillin allergy de-labelling inpatient pathway: identifying the barriers and enablers

Background

Non-allergist delivered PADL is supported by UK and World Health Organization guidelines but is not yet routine in UK hospitals. Understanding the views of healthcare workers (HCWs) on managing patients with penA records and exploring perspectives on delivering a PADL inpatient pathway are required to inform the development of non-allergist delivered PADL pathways.

Objective

To explore the perspectives of non-allergist HCWs working in medical specialties on managing patients with penA records, and to explore the enablers and barriers to embedding PADL as a standard of care for inpatients.

Methods

Semi-structured interviews with doctors, nurses, pharmacists and medicines optimization pharmacy technicians working in a district general hospital in the UK. Thematic analysis was used to analyse the data.

Results

The PADL pathway was considered a shared responsibility of the multidisciplinary team, which needed to be structured and supported by a framework. PADL aligns with HCW roles but time to deliver PADL was a barrier. Training for HCWs on the benefits of PADL and delivering PADL for those patients where a penicillin might be beneficial during the current episode of care would both motivate HCWs to deliver PADL.

Discussion and conclusion

The PADL pathway was acceptable to HCWs and aligned with their roles and current healthcare processes but their capacity to deliver PADL in a time pressured environment was a significant barrier.

Sepsis Stewardship: The Puzzle of Antibiotic Therapy in the Context of Individualization of Decision Making

The main recent change observed in the field of critical patient infection has been universal awareness of the need to make better use of antimicrobials, especially for the most serious cases, beyond the application of simple and effective formulas or rigid protocols. The increase in resistant microorganisms, the quantitative increase in major surgeries and interventional procedures in the highest risk patients, and the appearance of a significant number of new antibiotics in recent years (some very specifically directed against certain mechanisms of resistance and others with a broader spectrum of applications) have led us to shift our questions from "what to deal with" to "how to treat". There has been controversy about how best to approach antibiotic treatment of complex cases of sepsis. The individualized and adjusted dosage, the moment of its administration, the objective, and the selection of the regimen are pointed out as factors of special relevance in a critically ill patient where the frequency of resistant microorganisms, especially among the Enterobacterales group, and the emergence of multiple and diverse antibiotic treatment alternatives have made the appropriate choice of antibiotic treatment more complex, requiring a constant updating of knowledge and the creation of multidisciplinary teams to confront new infections that are difficult to treat. In this article, we have reviewed the phenomenon of the emergence of resistance to antibacterials and we have tried to share some of the ideas, such as stewardship, sparing carbapenems, and organizational, microbiological, pharmacological, and knowledge tools, that we have considered most useful and effective for individualized decision making that takes into account the current context of multidrug resistance. The greatest challenge, therefore, of decision making in this context lies in determining an effective, optimal, and balanced empirical antibiotic treatment.

Invasive group A streptococcal disease

We report on two children who had presented in a poor clinical state after an initial bout of cough, sore throat and fever for a few days. Both of them had multisystemic involvement with fluid-refractory septic shock requiring ionotropic support, intubation and care in the paediatric intensive care unit. Recent significant rise in scarlet fever has led to a significant increase in the number of invasive group A streptococcal infections with increased mortality in paediatric patients. Both of them had co-infection with influenza, which could have led to an increased risk of invasive group A streptococcal (iGAS) infection. After prompt treatment, including early initiation of antibiotics, they both recovered well. To our knowledge, there are no reported cases of iGAS infection from the UK in any medical journal though the fatal cases have been reported to the health statistics department by various National Health Service trusts individually.

Approach for delabeling beta-lactam allergy in children

A considerable number of pediatric patients treated with beta-lactam (BL) antibiotics develop delayed onset of skin rashes during the course of treatment. Although the most frequent cause of these symptoms is infectious, many cases are labeled as allergic reactions to these drugs. BL allergy labels could have a negative impact, as they imply avoidance of this group of drugs and the use of second-line antibiotics, leading to a potential increase in adverse effects and the utilization of less effective therapies. This constitutes a major public health concern and economic burden, as the use of broad-spectrum antibiotics can result in multidrug-resistant organisms and prolonged hospital stays. Therefore, it is crucial to delabel patients during childhood to avoid false labeling in adult life. Although the label of BL allergy is among the most frequent causes of allergy referral, its management remains controversial, and new diagnostic perspectives are changing the paradigm of managing BL allergies in children. Traditionally, drug provocation testing (DPT) was exclusively performed in patients who had previously obtained negative results from skin tests (STs). However, the sensitivity of STs is low, and the role of in vitro testing in the pediatric population is not well defined. Recent studies have demonstrated the safety of direct DPT without prior ST or serum tests for pediatric patients who report a low-risk reaction to BLs, which is cost-effective. However, there is still a debate on the optimal allergic workup to be performed in children with a benign immediate reaction and the management of children with severe cutaneous adverse drug reactions. In this review, we will discuss the impact of the label of BL allergy and the role of the different tools currently available to efficiently address BL allergy delabeling in children.

Challenges and opportunities related to penicillin allergy in the Veterans Health Administration: a narrative review

The presence of a penicillin allergy label in a patient's medical chart is associated with negative clinical and economic outcomes. Given that less than 10% of reported reactions are truly immunoglobulin E-mediated, removal of unverified penicillin allergy labels is a public health priority and an area of ongoing implementation research. The Veterans Health Administration (VHA) is the largest integrated healthcare system in the United States, with almost 9 million veterans currently enrolled. However, studies analyzing the impact of the penicillin allergy label in this population are limited to single facilities and largely focus on short-term outcomes of allergy documentation correction, usage of β-lactams, and avoidance of antibiotic-related side effects. Broader, national VHA studies focusing on health outcomes and costs are lacking. As with non-VHA facilities, penicillin allergy evaluations are limited owing to the absence of formal allergy/immunology services at most VHA facilities. Pharmacy-driven screening and referral for clinic-based penicillin skin testing is a promising and frequently discussed modality in the literature, but its scalability within the VHA is not yet proven. Broader, evidence-based strategies that can be adapted to the available resources of individual VHA facilities, including those without on-site access to allergy providers, are needed.

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.

Delabelling multiple antibiotic allergy: Practical issues

With the growing incidence of multi-drug resistant organisms, delabelling incorrect antibiotic allergies has become an integral part of antimicrobial stewardship worldwide. For example, around 90% of penicillin allergy labels are found to be inaccurate following a full allergy work-up, which deprive patients the use of effective first-line penicillin antibiotics and increase the risk of antimicrobial resistance with the use of other extended spectrum non-penicillin antimicrobials. Significant numbers of adult and paediatric patients over time are labelled with multiple penicillin and non-penicillin antibiotic allergies often during inappropriate antimicrobial use, resulting in a label of “multiple antibiotic allergy”. In contrast to delabelling penicillin allergy where oral direct provocation tests can be used for low-risk, mild reactions, and sensitivity/specificity/positive and negative predictive values of skin tests have been demonstrated, diagnostic tests for multiple antibiotic allergy often require the use of a combination of in-vivo and in-vitro tests across different antimicrobial classes for evaluation. Shared decision making with patients and informed consent are also needed when prioritising which drugs to delabel first, balancing the risks, benefits of testing vs. interim use of alternative antibiotics. Similar to delabelling penicillin allergy, the cost-effectiveness of delabelling multiple drug allergies is unknown.