Update on the evaluation of hypersensitivity reactions to betalactams

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.

Anaphylaxis to beta-lactam antibiotics at pediatric age: Six-year survey

INTRODUCTION

Beta-lactams are the most frequently used antibiotics in pediatric age. Anaphylactic reactions may occur and need to be properly studied, but studies in children are scarce.

OBJECTIVE

Characterization of case reports of anaphylaxis in children referred to an allergy department with suspected beta-lactams hypersensitivity.

MATERIALS AND METHODS

Retrospective analysis of all children referred to our Drug Allergy Center with suspected beta-lactams hypersensitivity between January 2011 and December 2016. Description of the drug allergy work-up performed studied according to standardized diagnostic procedures of ENDA/EAACI, including specific-IgE assay, skin prick and intradermal tests and diagnostic/alternative drug challenge tests.

RESULTS

146 children with suspected beta-lactams hypersensitivity were studied, and in 21 (14.4%) the diagnosis was confirmed. In all of them, except for three children, an alternative beta-lactam was found. In seven children (33.3% of those with confirmed beta-lactams hypersensitivity) anaphylaxis was confirmed, and all of them described reactions with cutaneous and respiratory or gastrointestinal involvement. The culprit drug was amoxicillin in six and flucloxacillin in one. In this sample, we also performed oral challenge with cefuroxime, being negative in all cases. Almost all cases of confirmed anaphylaxis (six from seven cases) were IgE mediated, with positive skin tests despite negative serum specific-IgE.

CONCLUSIONS

Allergic reactions to beta-lactams, although rare in children, require a detailed clinical history and a specialized drug allergy work-up to allow a correct diagnosis as well as to avoid the possibility of a potential life-threatening reaction and provide alternative drugs.

Antibiotic allergy

Antibiotics are the commonest cause of life-threatening immune-mediated drug reactions that are considered off-target, including anaphylaxis, and organ-specific and severe cutaneous adverse reactions. However, many antibiotic reactions documented as allergies were unknown or not remembered by the patient, cutaneous reactions unrelated to drug hypersensitivity, drug-infection interactions, or drug intolerances. Although such reactions pose negligible risk to patients, they currently represent a global threat to public health. Antibiotic allergy labels result in displacement of first-line therapies for antibiotic prophylaxis and treatment. A penicillin allergy label, in particular, is associated with increased use of broad-spectrum and non-β-lactam antibiotics, which results in increased adverse events and antibiotic resistance. Most patients labelled as allergic to penicillins are not allergic when appropriately stratified for risk, tested, and re-challenged. Given the public health importance of penicillin allergy, this Review provides a global update on antibiotic allergy epidemiology, classification, mechanisms, and management.

Mild to moderate hypersensitivity reactions to beta-lactams in children: a single-centre retrospective review

OBJECTIVE

Beta-lactam (BL) antibiotics are the most reported drugs in hypersensitivity reactions in children. More than 90% of these children tolerate the suspected drug after diagnostic work-up. Skin tests (STs) show low sensitivity. Our aim was to assess the performance of drug provocation tests (DPTs) without previous ST in mild and moderate delayed reactions and to propose a new DPT protocol.

DESIGN OF THE STUDY

Charts from 213 children under 15 years of age referred for suspected BL allergy from 2011 to 1013 were reviewed. Prick, intradermal and patch tests were performed with major determinant penicilloyl-polylysine, minor determinant mixture, amoxicillin (AMX), cefuroxime, penicillin G and AMX-clavulamate. Children with negative skin tests underwent DPT. After an initial full dose of antibiotic, DPT was carried on for 3 days at home in patients reacting within the first 3 days of treatment. If the reaction took place from day 4 on of treatment, patients took the antibiotic for 5 days.

RESULTS

We included 108 girls and 105 boys. Mean age at the time of reaction was 3.66±3.06 years. 195 patients (91.5%) reacted to one BL. 154 reactions (67.2%) were non-immediate. Mild to moderate skin manifestations were most frequently reported. AMX-clavulanate was the most frequently involved (63.4%). DPT confirmed the diagnosis of drug hypersensitivity in 17 (7.3%) cases. These 17 patients had negative ST.

CONCLUSION

In mild and moderate cases of BL hypersensitivity, diagnosis can be performed by DPT without previous ST.

Suspected Reaction with Cephalosporin May Be a Predictive Factor for β-Lactam Allergy in Children

BACKGROUND

Most children diagnosed with β-lactam allergy based only on history are not truly allergic, and mislabeling leads to use of less effective and more costly alternative broader-spectrum antibiotics, significantly increasing drug resistance.

OBJECTIVE

To determine the frequency and risk factors of confirmed allergy in patients with β-lactam allergy reported by parents or their doctors and evaluate cross-reactivity between β-lactams in children with confirmed allergy.

METHOD

Sixty-seven children with suspected β-lactam allergy were evaluated via history, sIgE measurements, skin tests, and drug provocation tests over a period of 5 years.

RESULTS

β-Lactam allergy was confirmed in 10 (14.9%) patients. Six patients had a positive intradermal test result to one or more of the penicillin skin test materials or ceftriaxone, 4 patients with negative skin test results had positive test results with suspected drugs. Age, gender, time interval between evaluation and the initial reaction, personal history of atopy, parental history of drug allergy, reaction type, and multiple drug allergy history were not significantly different between allergic and tolerant patients. For culprit drugs, there was a significant different between the 2 groups; the rate of confirmed diagnosis was significantly higher for cephalosporins such as ceftriaxone, cefuroxime, and cefprozil (p = 0.03). Three patients with allergy to penicillin tolerated cefuroxime; in 4 patients with selective allergy to ceftriaxone tolerated cephalosporins with a dissimilar side chain (cefadroxil, cefuroxime, cefaclor, and cefdinir).

CONCLUSION

Our study indicates that most patients with a suspected β-lactam allergy tolerated this drug. An appropriate diagnostic allergy workup may prevent the use of less effective and more expensive alternatives.

Controversies in Drug Allergy: Beta-Lactam Hypersensitivity Testing

All beta-lactam use is associated with a certain rate of adverse reactions. Many of these adverse reactions result in an allergy to the beta-lactam being entered into the patient's medical record. Unfortunately, only a small minority of these recorded allergies are clinically significant immunologically mediated drug hypersensitivity. An unconfirmed allergy to beta-lactams is a significant public health risk, because patients so labeled typically do not receive narrow-spectrum penicillins and cephalosporins when clinically indicated. The alternative antibiotics they receive result in poorer clinical outcomes, increased incidence of serious antibiotic-resistant infections, prolonged hospitalizations, and greater health care utilization. There is a wide variation in beta-lactam allergy incidence and prevalence around the world, based in part on the specific beta-lactams used and overused. There is a wide variation in specific protocols used to confirm current tolerance of beta-lactams and remove these inaccurate allergy reports. Harmonizing testing protocols, when possible, may lead to more widespread use of narrow-spectrum beta-lactams, when clinically indicated, and improve patient safety worldwide. Further research is needed to better understand the regional differences in reporting beta-lactam allergy as this relates to regional differences in beta-lactam use and overuse, the frequency of clinically significant immunologically mediated beta-lactam hypersensitivity, and the optimal testing strategies to confirm current tolerance, based on presenting clinical symptoms.

The anti-penicillin antibodies levels in sensitive and insensitive people to intradermal skin test

BACKGROUND

The hypersensitivity reaction to penicillin is a public health problem. Immunological responses to penicillin and other beta-lactam antibiotics can be classified into immediate and non-immediate responses. The immediate hypersensitivity is mediated by IgE; however, the non-immediate sensitivity is facilitated by other isotypes of antibody or T lymphocytes.

OBJECTIVE

This research detected the non-IgE antibody value against penicillin in allergic and normal people.

METHODS

Thirty-eight samples from patients with positive or negative intradermal skin testing results of penicillin allergy were included in this study. The total antibody and IgM levels against penicillin G were defined by in-house ELISA test.

RESULTS

The results showed a significant (P< 0.05) elevation in total immunoglobulin and non-IgM anti-penicillin antibody of sensitive groups; however, the anti-penicillin IgM was significantly greater in non-sensitive peoples.

CONCLUSIONS

Although the sensitized people to penicillin cannot be certainly detected with the total antibody, specific IgG and IgM value against penicillin, these values are good indicators for prediction of immediate and late response of the immune system to penicillin.

Enhancing antibiotic stewardship by tackling "spurious" penicillin allergy

Approximately 90-99% of patients with a label of penicillin allergy (PenA) are not allergic when comprehensively investigated. An inaccurate label of PenA has major public health implications-longer hospital stay, more frequent hospital admissions, greater use of fluoroquinolones, glycopeptides, cephalosporins and other expensive antibiotics resulting in significantly higher costs to the health service and predisposing to Clostridium difficile, methicillin-resistant Staphylococcus aureus infections and vancomycin-resistant enterococcus. We describe lessons learnt from recent studies regarding possible reasons contributing to an inaccurate label of PenA as well as propose a concerted multidisciplinary approach to address this important public health problem. Given the unmet need for allergy services in the UK and several other countries and knowledge gaps regarding PenA amongst healthcare professionals, we describe the potential role for a computerized clinical decision support system to enable non-specialists rapidly identify and de-label "low-risk" hospitalized patients with a label of PenA thereby obviating the need for allergy tests. This approach however needs rigorous evaluation for feasibility, safety, patient and physician acceptability, cost-effectiveness and its compatibility with information technology systems currently employed in the health service.

Prospective assessment of diagnostic tests for pediatric penicillin allergy: From clinical history to challenge tests

BACKGROUND

Diagnostic guidelines for penicillin allergy in children recommend cumbersome protocols based partially on data from adults, which may be suboptimal for pediatric use.

OBJECTIVE

To assess the accuracy of tools for diagnosis of penicillin allergy in children.

METHODS

A prospective, multicenter study was conducted in children with reported adverse events related to penicillin, excluding severe reactions. All patients underwent a uniform diagnostic protocol that consisted of clinical history, skin tests, serum specific IgE (sIgE), and, regardless of these results, drug provocation tests (DPTs).

RESULTS

A total of 732 children (mean age, 5.5 years; 51.2% males) completed the allergy workup, including DPTs. Amoxicillin triggered 96.9% of all reactions. None of the patients with an immediate index reaction (IR) developed a reaction on DPT. Penicillin allergy was confirmed in 35 children (4.8%): 6 immediate reactions (17%) and 29 nonimmediate reactions (83%) on the DPT. No severe reactions were recorded. The allergist diagnosis based on the clinical history was not associated with the DPT final outcome. In 30 of 33 allergic patients (91%), the results of all skin tests and sIgE tests were negative. A logistic regression model identified the following to be associated with penicillin allergy: a family history of drug allergy (odds ratio [OR], 3.03; 95% confidence interval [CI], 1.33-6.89; P = .008), an IR lasting more than 3 days vs 24 hours or less (OR, 8.96; 95% CI, 2.01-39.86; P = .004), and an IR treated with corticosteroids (OR, 2.68; 95% CI, 1.30-5.54; P = .007).

CONCLUSION

Conventional predictors of allergy to penicillin performed weakly. The authors propose straightforward penicillin provocation testing in controlled, experienced centers for the diagnosis of nonsevere penicillin allergy in children.

Antibiotic Allergy in Pediatrics

The overlabeling of pediatric antibiotic allergy represents a huge burden in society. Given that up to 10% of the US population is labeled as penicillin allergic, it can be estimated that at least 5 million children in this country are labeled with penicillin allergy. We now understand that most of the cutaneous symptoms that are interpreted as drug allergy are likely viral induced or due to a drug-virus interaction, and they usually do not represent a long-lasting, drug-specific, adaptive immune response to the antibiotic that a child received. Because most antibiotic allergy labels acquired in childhood are carried into adulthood, the overlabeling of antibiotic allergy is a liability that leads to unnecessary long-term health care risks, costs, and antibiotic resistance. Fortunately, awareness of this growing burden is increasing and leading to more emphasis on antibiotic allergy delabeling strategies in the adult population. There is growing literature that is used to support the safe and efficacious use of tools such as skin testing and drug challenge to evaluate and manage children with antibiotic allergy labels. In addition, there is an increasing understanding of antibiotic reactivity within classes and side-chain reactions. In summary, a better overall understanding of the current tools available for the diagnosis and management of adverse drug reactions is likely to change how pediatric primary care providers evaluate and treat patients with such diagnoses and prevent the unnecessary avoidance of antibiotics, particularly penicillins.

Evaluation of IFN-γ Enzyme-linked Immunospot Assay (ELISPOT) as a First-line Test in the Diagnosis of Non-Immediate Hypersensitivity to Amoxicillin and Penicillin

The current diagnostic algorithm for beta-lactam allergy is based on skin and provocation tests, both of which carry a certain risk of inducing hypersensitivity reactions. Thus, non-invasive in vitro tests reliable enough to replace skin and provocation tests at least in a portion of patients are desirable. We aimed to verify the utility of IFN-γ ELISPOT as a first-line test in patients with suspected non-immediate hypersensitivity reaction to amoxicillin (AMX) and penicillin (PNC). The prospective observational study included 24 patients with recent, suspected non-immediate hypersensitivity reaction to AMX or PNC and 6 recently-exposed healthy subjects. In vitro tests were performed in all patients and healthy subjects: a) IFN-γ ELISPOT with PNC, AMX and amoxicillin plus clavulanic acid (AMX-CL); b) penicillin specific IgE; c) basophil activation test (BAT). Skin and provocation tests followed only in certain patients. IFN-γ ELISPOT results with PNC and AMX stimulation did not differ from the unstimulated condition. The highest IFN-γ responses to AMX-CL were close to previously published criteria in three patients; one of which had true hypersensitivity according to drug provocation tests. Five patients with confirmed hypersensitivity by skin tests showed no response to the culprit antibiotic on IFN-γ ELISPOT assay. Our results did not support the utility of IFN-γ ELISPOT in the diagnosis of mild, non-immediate hypersensitivity to amoxicillin and penicillin.

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.

Positive Skin Test or Specific IgE to Penicillin Does Not Reliably Predict Penicillin Allergy

INTRODUCTION

According to guidelines, patients are diagnosed with penicillin allergy if skin test (ST) result or specific IgE (s-IgE) to penicillin is positive. However, the true sensitivity and specificity of these tests are presently not known.

OBJECTIVE

To investigate the clinical relevance of a positive ST result and positive s-IgE and to study the reproducibility of ST and s-IgE.

METHODS

A sample of convenience of 25 patients with positive penicillin ST results, antipenicillin s-IgE results, or both was challenged with their culprit penicillin. Further 19 patients were not challenged, but deemed allergic on the basis of a recent anaphylactic reaction or delayed reactions to skin testing. Another sample of convenience of 18 patients, 17 overlapping with the 25 challenged, with initial skin testing and s-IgE (median, 25; range, 3-121), months earlier (T_-1), was repeat skin tested and had s-IgE measured (T₀), and then skin tested and had s-IgE measured 4 weeks later (T₁).

RESULTS

Only 9 (36%) of 25 were challenge positive. There was an increased probability of being penicillin allergic if both ST result and s-IgE were positive at T₀. Positive ST result or positive s-IgE alone did not predict penicillin allergy. Among the 18 patients repeatedly tested, 46.2% (12 of 25) of positive ST results at T_-1 were reproducibly positive at T₀. For s-IgE, 54.2% (14 of 24) positive measurements were still positive at T₀ and 7 converted to positive at T₁.

CONCLUSIONS

The best predictor for a clinically significant (IgE-mediated) penicillin allergy is a combination of a positive case history with simultaneous positive ST result and s-IgE or a positive challenge result.

Efficacy and Safety of 5-Day Challenge for the Evaluation of Nonsevere Amoxicillin Allergy in Children

BACKGROUND

Penicillin allergy is the most frequent drug allergy, among which aminopenicillins are reputed for causing delayed rashes in children, particularly in the context of viral infections. Despite a negative allergy evaluation, a significant proportion of individuals continue to avoid penicillin antibiotics for fear of an allergic reaction.

OBJECTIVE

To evaluate the safety and efficacy of a 5-day challenge to amoxicillin and the proportion of subsequent use of amoxicillin.

METHODS

Pediatric patients with a history of a reaction to amoxicillin were prospectively recruited in the study. All patients were challenged, and those with negative immediate challenges underwent an ambulatory 5-day challenge to amoxicillin to rule out nonimmediate reactions. Patients were called 2 years after their initial allergy evaluation to assess subsequent amoxicillin use and tolerance.

RESULTS

One hundred thirty children with a history of amoxicillin allergy underwent a graded drug provocation test (DPT) to amoxicillin. Three patients had a positive immediate challenge, 3 had a positive nonimmediate challenge, and 2 were equivocal. Of the 122 patients with a negative challenge, 114 (93.4%) were reached 2 years after their initial allergy evaluation: 75 had used antibiotics since, of which only 1 (1.3%) had refused to reuse amoxicillin because of fear of an allergic reaction. Finally, the 5-day DPT resulted in a 24.1% decrease in future penicillin avoidance compared with classical single-dose graded DPT performed for 1 day in a historical cohort (P < .0001).

CONCLUSION

The 5-day challenge is a safe and effective way to rule out nonimmediate amoxicillin allergy, and it ensures better compliance with future penicillin use.

Non-immediate-reading skin tests and prolonged challenges in non-immediate hypersensitivity to beta-lactams in children

BACKGROUND

A minority of children reporting non-immediate reactions to beta-lactams (BLs) are allergic. Allergy workup usually includes late-reading (48-72 hours) skin tests (ST) and short (1-3 days) drug provocation tests (DPT), regardless of the chronology of the index reaction. The sensitivity of hyper-late-reading (≥6-7 days) ST and of prolonged DPT for the diagnosis of non-immediate hypersensitivity to BLs is yet to be determined.

OBJECTIVES

To establish the diagnostic values of late-reading ST and hyper-late-reading ST and of prolonged DPT in children reporting non-immediate reactions to BLs.

METHODS

Prospective assessment of children reporting non-immediate reactions to BLs with late- and additional hyper-late-reading intradermal (ID) and patch tests, and if negative, with prolonged DPT.

RESULTS

Five hundred and fifty children reporting reactions to a single or several BLs (674 suspected BLs) were included. Non-immediate hypersensitivity to BLs was diagnosed in 63 children (11.5%), reporting 66 reactions (9.8%), based on responses in ST (n = 17, 25.8%: 5 to ID, 8 to patch tests, and 4 to both tests), DPT (n = 43, 65.2%), and clinical history (n = 6, 9.1%), including 3/9 children with severe cutaneous adverse reactions. Skin test positivity was observed after the 6-7th day in 14/17 children, and DPT positivity after a median time of 3 days. No severe reaction was observed after ST or during prolonged DPT.

CONCLUSION

Additional hyper-late-reading of ST enhanced their positivity. However, their overall sensitivity remained weak, especially in non-severe cases. Prolonged DPT are safe and may improve the performance of DPT in the diagnosis of non-immediate hypersensitivity to BLs.

Patterns of anaphylaxis after diagnostic workup: A follow-up study of 226 patients with suspected anaphylaxis

BACKGROUND

Most published studies on anaphylaxis are retrospective or register based. Data on subsequent diagnostic workup are sparse. We aimed to characterize patients seen with suspected anaphylaxis at the emergency care setting (ECS), after subsequent diagnostic workup at our Allergy Center (AC).

METHODS

Prospective study including patients from the ECS, Odense University Hospital, during May 2013-April 2014. Possible anaphylaxis cases were daily identified based on a broad search profile including history and symptoms in patient records, diagnostic codes and pharmacological treatments. At the AC, all patients were evaluated according to international guidelines.

RESULTS

Among 226 patients with suspected anaphylaxis, the diagnosis was confirmed in 124 (54.9%) after diagnostic workup; 118 of the 124 fulfilled WAO/EAACI criteria of anaphylaxis at the ECS, while six were found among 46 patients with clinical suspicion but not fulfilling the WAO/EAACI criteria at the ECS. The estimated incidence rate of anaphylaxis was 26 cases per 100 000 person-years and the one-year period prevalence was 0.04%. The most common elicitor was drugs (41.1%) followed by venom (27.4%) and food (20.6%). In 13 patients (10.5%), no elicitor could be identified. Mastocytosis was diagnosed in 7.7% of adult patients and was significantly associated with severe anaphylaxis. Atopic diseases were significantly associated only with food-induced anaphylaxis. Cofactors were present in 58.1% and were significantly associated with severe anaphylaxis.

CONCLUSION

A broad search profile in the ECS and subsequent diagnostic workup is important for identification and classification of patients with anaphylaxis. Evaluation of comorbidities and cofactors is important.

A clinical decision-making algorithm for penicillin allergy

BACKGROUND

About 10% of subjects report suspected penicillin allergy, but 85-90% of these patients are not truly allergic and could safely receive beta-lactam antibiotics Objective: To design and validate a clinical decision-making algorithm, based on anamnesis (chronology, severity, and duration of the suspected allergic reactions) and reaching a 100% sensitivity and negative predictive value, to assess allergy risk related to a penicillin prescription in general practise.

STUDY DESIGN AND METHODS

All patients were included prospectively and explorated based on ENDA/EAACI recommendations. Results of penicillin allergy work-up (gold standard) were compared with results of the algorithm.

RESULTS

Allergological work-up diagnosed penicillin hypersensitivity in 41/259 patients (15.8%) [95% CI: 11.5-20.3]. Three of these patients were diagnosed as having immediate-type hypersensitivity to penicillin, but had been misdiagnosed as low risk patients using the clinical algorithm. Thus, the sensitivity and negative predictive value of the algorithm were 92.7% [95% CI: 80.1-98.5] and 96.3% [95% CI: 89.6-99.2], respectively, and the probability that a patient with true penicillin allergy had been misclassified was 3.7% [95% CI: 0.8-10.4].

CONCLUSIONS

Although the risk of misclassification is low, we cannot recommend the use of this algorithm in general practice. However, the algorithm can be useful in emergency situations in hospital settings. Key messages True penicillin allergy is considerably lower than alleged penicillin allergy (15.8%; 41 of the 259 patients with suspected penicillin allergy). A clinical algorithm based on the patient's clinical history of the supposed allergic event to penicillin misclassified 3/41 (3.7%) truly allergic patients.

Confronting the Challenge of Beta-Lactam Allergies: A Quasi-Experimental Study Assessing Impact of Pharmacy-Led Interventions

OBJECTIVE

To improve allergy history documentation and increase the use of beta-lactams when appropriate in patients with a reported beta-lactam allergy.

METHODS

This pre-post study was conducted at a 167-bed tertiary care community hospital and evaluated multidisciplinary interventions on allergy documentation and antibiotic selection. Interventions included education, creation of local practice guidelines, and modified practices for pharmacists and pharmacy technicians. Inpatients with a reported beta-lactam allergy receiving at least 1 antibiotic for >24 hours were included; first admissions were assessed. Primary outcomes were documentation of reaction type and percentage of patients receiving non-beta-lactam therapy. Secondary outcomes included documentation of previously tolerated beta-lactams, modification of non-beta-lactam therapy, discharge antibiotics, and adverse reactions.

RESULTS

A total of 179 patients were included, 91 preintervention and 88 postintervention. No significant differences were observed between the before versus after groups in the percentage of patients with documentation of reaction type (90.1% vs 89.8%, P = .940) or the overall percentage of patients receiving non-beta-lactams (86.8% vs 84.1%, P = .605). However, significantly more patients in the after phase had documentation of previously tolerated beta-lactams (8.8% vs 28.4%, P = .001), and among patients receiving a non-beta-lactam, a greater percentage was subsequently switched to a beta-lactam (11.4% vs 25.7%, P = .022). One allergic reaction was documented during the study, which occurred in the before phase.

CONCLUSION

Multidisciplinary education and local guideline implementation led by pharmacists may improve allergy documentation and antibiotic selection in patients with reported beta-lactam allergies.

Is a positive intracutaneous test induced by penicillin mediated by histamine? A cutaneous microdialysis study in penicillin-allergic patients

Background

Diagnostic workup of penicillin allergy comprises skin testing with penicillins, and patients are deemed allergic if skin test is positive. However, the literature suggests that skin test-positive patients may be challenge-negative, indicating that the skin test may be falsely positive.

Objective

To investigate real-time histamine release from a positive intracutaneous test induced by penicillin in patients with positive and negative challenges to penicillin.

Methods

Skin microdialysis was performed in 21 penicillin-allergic patients with positive skin test, 13 non-allergic volunteers serving as negative controls, and 7 grass pollen-allergic patients serving as positive controls. Histamine was measured by microdialysis after skin test with penicillin/grass/NaCl. Penicillin challenge was subsequently performed in 12 of the patients.

Results

Only 10/21 patients (47.6%) were skin test positive at microdialysis. During microdialysis 13 single intracutaneous tests were positive and histamine was detected in 4/13 occurring in four challenge positive patients. Thirteen/21 patients (61.9%) were deemed allergic to penicillin; eight had positive skin test. Two patients with positive skin test were challenge negative. In grass pollen allergic patients, 7/7 had a positive intracutaneous test to grass and all released histamine in the wheals. All 13 negative controls had negative intracutaneous test to penicillin and no histamine release.

Conclusion

Histamine was only detected in the minority of positive intracutaneous tests with penicillin in penicillin-allergic patients. Other mediators may be involved.

The 3 Cs of Antibiotic Allergy-Classification, Cross-Reactivity, and Collaboration

Antibiotic allergy labeling is highly prevalent and negatively impacts patient outcomes and antibiotic appropriateness. Reducing the prevalence and burden of antibiotic allergies requires the engagement of key stakeholders such as allergists, immunologists, pharmacists, and infectious diseases physicians. To help address this burden of antibiotic allergy overlabeling, we review 3 key antibiotic allergy domains: (1) antibiotic allergy classification, (2) antibiotic cross-reactivity, and (3) multidisciplinary collaboration. We review the available evidence and research gaps of currently used adverse drug reaction classification systems, antibiotic allergy cross-reactivity, and current and future models of antibiotic allergy care.

Cross-reactivity in β-Lactam Allergy

β-Lactam drugs (penicillins, amoxicillin, and cephalosporins) account for 42.6% of all severe drug-induced anaphylaxis. In this review, we focus on clinically significant immunologic cross-reactivity in patients with confirmed penicillin allergy to cephalosporins, and the structural involvement of the R₁ and R₂ chemical side chains of the cephalosporins causing IgE-mediated cross-reactivity with penicillin and other cephalosporins. Skin tests predict IgE-mediated reactions and showed cross-reactivity between penicillins and early generation cephalosporins that shared side chains, but confirmatory challenge data are lacking. Later-generation cephalosporins, which have distinct side chains, do not have any skin test cross-reactivity with penicillin/amoxicillin. There is debate as to the involvement of R₂ side chains as the antigenic determinants that cause IgE-mediated hypersensitivity with various cephalosporins. Avoidance of cephalosporins, when they are the drug of choice in a penicillin-allergic individual, results in significant morbidity that outweighs the low risk of anaphylaxis. We conclude that there is ample evidence to allow the safe use of cephalosporins in patients with isolated confirmed penicillin or amoxicillin allergy.

A New Pathway for Protein Haptenation by β-Lactams

The covalent binding of β-lactams to proteins upon photochemical activation has been demonstrated by using an integrated approach that combines photochemical, proteomic and computational studies, selecting human serum albumin (HSA) as a target protein and ezetimibe (1) as a probe. The results have revealed a novel protein haptenation pathway for this family of drugs that is an alternative to the known nucleophilic ring opening of β-lactams by the free amino group of lysine residues. Thus, photochemical ring splitting of the β-lactam ring, following a formal retro-Staudinger reaction, gives a highly reactive ketene intermediate that is trapped by the neighbouring lysine residues, leading to an amide adduct. For the investigated 1/HSA system, covalent modification of residues Lys414 and Lys525, which are located in sub-domains IIIA and IIIB, respectively, occurs. The observed photobinding may constitute the key step in the sequence of events leading to photoallergy. Docking and molecular dynamics simulation studies provide an insight into the molecular basis of the selectivity of 1 for these HSA sub-domains and the covalent modification mechanism. Computational studies also reveal positive cooperative binding of sub-domain IIIB that explains the experimentally observed modification of Lys414, which is located in a barely accessible pocket (sub-domain IIIA).

Clinical outcomes following inpatient penicillin allergy testing: A systematic review and meta-analysis

BACKGROUND

A documented penicillin allergy is associated with increased morbidity including length of hospital stay and an increased incidence of resistant infections attributed to use of broader-spectrum antibiotics. The aim of the systematic review was to identify whether inpatient penicillin allergy testing affected clinical outcomes during hospitalization.

METHODS

We performed an electronic search of Ovid MEDLINE/PubMed, Embase, Web of Science, Scopus, and the Cochrane Library over the past 20 years. Inpatients having a documented penicillin allergy that underwent penicillin allergy testing were included.

RESULTS

Twenty-four studies met eligibility criteria. Study sample size was between 24 and 252 patients in exclusively inpatient cohorts. Penicillin skin testing (PST) with or without oral amoxicillin challenge was the main intervention described (18 studies). The population-weighted mean for a negative PST was 95.1% [CI 93.8-96.1]. Inpatient penicillin allergy testing led to a change in antibiotic selection that was greater in the intensive care unit (77.97% [CI 72.0-83.1] vs 54.73% [CI 51.2-58.2], P<.01). An increased prescription of penicillin (range 9.9%-49%) and cephalosporin (range 10.7%-48%) antibiotics was reported. Vancomycin and fluoroquinolone use was decreased. Inpatient penicillin allergy testing was associated with decreased healthcare cost in four studies.

CONCLUSIONS

Inpatient penicillin allergy testing is safe and effective in ruling out penicillin allergy. The rate of negative tests is comparable to outpatient and perioperative data. Patients with a documented penicillin allergy who require penicillin should be tested during hospitalization given its benefit for individual patient outcomes and antibiotic stewardship.

Allergy test outcomes in patients self-reported as having penicillin allergy: Two-year experience

BACKGROUND

Penicillin allergy is associated with increased antibiotic resistance and health care costs. However, most patients with self-reported penicillin allergy are not truly allergic.

OBJECTIVE

To summarize our experience with allergy tests in patients with a history of penicillin allergy and to compare them with the results of other groups.

METHODS

We retrospectively reviewed all patients with a suspected clinical history of penicillin allergy referred to the Drug Allergy Unit at University College London Hospital between March 2013 and June 2015.

RESULTS

In total, 84 patients were reviewed. The index drugs included: unidentified penicillin (n = 44), amoxicillin (n = 17), amoxicillin-clavulanic acid (n = 13), flucloxacillin (n = 4), and other penicillins (ampicillin, benzylpenicillin, piperacillin-tazobactam; n = 7). Allergy diagnoses were confirmed in 24 patients (28.6%) (16 to penicillin, 3 to flucloxacillin, 5 to clavulanic acid). Twenty-two patients (91.7%) had allergy diagnosed by positive skin test results. Two patients (8.3%) developed IgE-mediated allergic symptoms during oral challenge (although the skin test results were negative). In vitro specific IgE test results for penicilloyl V, penicilloyl G, and amoxicilloyl were positive in 3 of 16 patients (18.8%). Moreover, reactions to cefuroxime were observed in 3 of 15 patients with penicillin allergy (20%). Selective clavulanic acid and flucloxacillin responders tolerated amoxicillin challenge. The interval between the index reaction and evaluation was shorter (P < .001), and the proportion of patients who could recall the name of the culprit drug was higher (P = .009) in the allergic group. Furthermore, histories of anaphylaxis (33.3%), urticaria, and/or angioedema (58.3%) were more common in the allergic group. Unspecified rashes (35.0%) and nonspecific symptoms (28.3%) predominated in the nonallergic group.

CONCLUSION

Only 28.6% of patients with self-reported penicillin allergy were confirmed to be allergic. Importantly, when the index drug is amoxicillin-clavulanic acid or flucloxacillin, the patients may tolerate amoxicillin.

[Hypersensitivity reactions to beta-lactam antibiotics]

Allergy to beta-lactam antibiotics is a common condition and about 10% of patients report being allergic to penicillin. However, this diagnosis is largely overestimated. Two types of allergy should be distinguished and include immediate hypersensitivity that can lead to anaphylactic shock and delayed hypersensitivity, ranging from the most common maculopapular exanthema to severe bullous toxidermia or life-threatening DRESS. Allergy challenge with oriented skin tests according to the clinical features, supplemented with oral challenge in the absence of contraindication, will confirm or invalidate the diagnosis of beta-lactam allergy and will help to identify if necessary safe alternatives to beta-lactams.

Non-immediate Cutaneous Reactions to Beta-Lactams: Approach to Diagnosis

Non-immediate cutaneous reactions (i.e., occurring at least 1 h after the initial drug administration), particularly maculopapular exanthemas and urticarial eruptions, are common during beta-lactam treatments. A T cell-mediated pathogenic mechanism has been demonstrated in some cutaneous reactions, such as maculopapular exanthema, fixed drug eruption, acute generalized exanthematous pustulosis, and drug-induced hypersensitivity syndrome. In the diagnostic work-up, patch testing is useful, together with delayed-reading intradermal testing. Patch tests are a simple and safe diagnostic tool, which in the case of severe reactions should be used as the first line of investigation. However, patch tests are less sensitive than intradermal tests, which are preferable in subjects with mild reactions. Lymphocyte transformation or activation tests and enzyme-linked immunosorbent spot assays can be used as complementary tests. In selected cases of mild or moderate reactions, displaying negative results in the aforesaid allergy tests, a graded challenge with the implicated beta-lactam can be performed.

Pro and Contra: Provocation Tests in Drug Hypersensitivity

Drug provocation test (DPT) is the controlled administration of a drug to diagnose immune- or non-immune-mediated drug hypersensitivity and the last step for accurate recognition of drug hypersensitivity reactions when the previous diagnostic evaluations are negative or unavailable. A DPT is performed only if other conventional tests fail to yield conclusive results. In each clinical presentation, "to provoke or not to provoke" a patient should be decided after careful assessment of the risk-benefit ratio. Well-defined benefits of DPT include confirmative exclusion of diagnoses of drug hypersensitivity and provision of safe alternatives. However, disadvantages such as safety, difficulty in interpretations of results, lack of objective biomarkers, risks of resensitization, efficiency in daily practice, and lack of standardized protocols, are poorly debated. This review summarizes the current published research concerning DPT, with particular emphasis on the advantages and disadvantages of DPT in an evidence-based manner.

In Vitro Diagnostic Testing for Antibiotic Allergy

Allergy to antibiotics is an important worldwide problem, with an estimated prevalence of up to 10% of the population. Reaction patterns for different antibiotics have changed in accordance with consumption trends. Most of the allergic reactions to antibiotics have been reported for betalactams, followed by quinolones and macrolides and, to a lesser extent, to others, such as metronidazole clindamycin and sulfonamides. The diagnostic procedure includes a detailed clinical history, which is not always possible and can be unreliable. This is usually followed by in vivo, skin, and drug provocation tests. These are not recommended for severe, potentially lifethreaten reactions or for drugs that are known to produce a high rate of false positive results. Given the limitations of in vivo tests, in vitro test can be helpful for diagnosis, despite having suboptimal sensitivity. The most highly employed techniques for diagnosing immediate reactions to antibiotics are immunoassays and basophil activation tests, while lymphocyte transformation tests are more commonly used to diagnose non-immediate reactions. In this review, we describe different in vitro techniques employed to diagnose antibiotic allergy.

The impact of penicillin allergy labels on antibiotic and health care use in primary care: a retrospective cohort study

BACKGROUND

Suspected penicillin allergy (Pen-A) is often not verified by diagnostic testing. In third line penicillin allergy labels were associated with prescription of broad spectrum antibiotics, hospital stay duration and readmission.

OBJECTIVE

Assess the impact of Pen-A labels on antibiotic and health care use in primary care.

METHODS

A retrospective cohort study was conducted in primary care in the Utrecht area, the Netherlands. All patients registered with a penicillin allergy on 31 December 2013 were selected from the General Practitioner Network database. Each patient with a Pen-A label was matched for age, gender, follow-up period with three patients without Pen-A label. Risk (OR) of receiving a reserve and second choice antibiotic, number and type of antibiotics prescribed during follow-up and number of GP contacts were compared between the two cohorts.

RESULTS

Of 196,440 patients, 1254 patients (0.6%) with a Pen-A label were identified and matched with 3756 patients without Pen-A label. Pen-A labels resulted in higher risk of receiving ≥1 antibiotic prescription per year (OR 2.56, 95% CI 2.05-3.20), ≥1 s choice antibiotic prescription per year (OR 2.21 95% CI 1.11-4.40), and ≥4 GP contacts per year (OR 1.71 95% CI 1.46-2.00). The chance of receiving tetracyclins (OR 2.24, 95% CI 1.29-3.89), macrolides/lincosamides/streptogamins (OR 8.69, 95% CI 4.26-17.73) and quinolones (OR 2.59, 95% CI 1.22-5.48) was higher in Pen-A patients.

CONCLUSIONS

In primary health care Pen-A labels are associated with increased antibiotic use, including second choice antibiotics, and more health care use.

Detection of drug-responsive B lymphocytes and antidrug IgG in patients with β-lactam hypersensitivity

BACKGROUND

Delayed-type β-lactam hypersensitivity develops in subset of patients. The cellular immunological processes that underlie the drug-specific response have been described; however, little is known about involvement of the humoral immune system. Thus, the aim of this study was to utilize piperacillin hypersensitivity as an exemplar to (i) develop cell culture methods for the detection of drug-specific B-cell responses, (ii) characterize drug-specific IgG subtypes and (iii) assess reactivity of IgG antibodies against proteins modified to different levels with piperacillin haptens.

METHODS

IgG secretion and CD19⁺ CD27⁺ expression on B cells were measured using ELISPOT and flow cytometry, respectively. A piperacillin-BSA adduct was used as an antigen in ELISA antibody binding studies. Adducts generated using different ratios of drug to protein were used to determine the degree of conjugation required to detect IgG binding.

RESULTS

B cells from hypersensitive patients, but not controls, were stimulated to secrete IgG and increase CD27 expression when cultured with soluble piperacillin. A piperacillin-BSA adduct with cyclized and hydrolysed forms of the hapten bound to eight lysine residues was used to detect hapten-specific IgG 1-4 subclasses in patient plasma. Hapten inhibition and the use of structurally unrelated hapten-BSA adducts confirmed antigen specificity. Antibody binding was detected with antigens generated at piperacillin/BSA ratios of 10:1 and above, which corresponded to a minimum epitope density of 1 for antibody binding.

CONCLUSION

These data show that antigen-specific B lymphocytes and T lymphocytes are activated in piperacillin-hypersensitive patients. Further work is needed to define the role different IgG subtypes play in regulating the iatrogenic disease.