A pilot study of penicillin skin testing in patients with a history of penicillin allergy admitted to a medical ICU

Penicillin allergy delabeling: Opportunities for implementation and dissemination

Although existing as a safety measure to prevent iatrogenic harm, unconfirmed penicillin allergy labels have a negative impact on personal and public health. One downstream effect of unconfirmed penicillin allergy is the continued emergence and transmission of resistant bacteria and their associated health care costs. Recognizing the consequences of inaccurate penicillin allergy labels, professional and public health organizations have started promoting the adoption of proactive penicillin allergy evaluations, with the ultimate goal of removing the penicillin allergy label when the allergy is disproved, also known as penicillin allergy "delabeling." A penicillin allergy evaluation includes a comprehensive allergy history often followed by drug challenge, sometimes with preceding skin testing. Currently, penicillin allergy delabeling is largely carried out by allergy specialists in outpatient settings. Penicillin allergy delabeling is performed on inpatients, albeit rarely, often at the time of need, as a point-of-care procedure. Access to penicillin allergy evaluation services is limited. Recent studies demonstrate the feasibility of expanding penicillin allergy evaluations and delabeling to internists, pediatricians, emergency medicine physicians, infectious diseases specialists, and clinical pharmacists. However, reducing the impact of mislabeled penicillin allergy will require comprehensive efforts and new investments. In this review, we summarize the current practices of penicillin allergy delabeling and discuss expansion opportunities for penicillin allergy delabeling as quality improvement.

Opportunities for penicillin allergy evaluation in dental clinics

OBJECTIVE

To evaluate opportunities for assessing penicillin allergies among patients presenting to dental clinics.

DESIGN

Retrospective cross-sectional study.

SETTING

VA dental clinics.

PATIENTS

Adult patients with a documented penicillin allergy who received an antibiotic from a dentist between January 1, 2015, and December 31, 2018, were included.

METHODS

Chart reviews were completed on random samples of 100 patients who received a noncephalosporin antibiotic and 200 patients who received a cephalosporin. Each allergy was categorized by severity. These categories were used to determine patient eligibility for 3 testing groups based on peer-reviewed algorithms: (1) no testing, (2) skin testing, and (3) oral test-dose challenge. Descriptive and bivariate statistics were used to compare facility and patient demographics first between true penicillin allergy, pseudo penicillin allergy, and missing allergy documentation, and between those who received a cephalosporin and those who did not at the dental visit.

RESULTS

Overall, 19% lacked documentation of the nature of allergic reaction, 53% were eligible for skin testing, 27% were eligible for an oral test-dose challenge, and 1% were contraindicated from testing. Male patients and African American patients were less likely to receive a cephalosporin.

CONCLUSIONS

Most penicillin-allergic patients in the VA receiving an antibiotic from a dentist are eligible for penicillin skin testing or an oral penicillin challenge. Further research is needed to understand the role of dentists and dental clinics in assessing penicillin allergies.

Penicillin causes non-allergic anaphylaxis by activating the contact system

Immediate hypersensitivity reaction (IHR) can be divided into allergic- and non-allergic-mediated, while “anaphylaxis” is reserved for severe IHR. Clinically, true penicillin allergy is rare and most reported penicillin allergy is “spurious”. Penicillin-initiated anaphylaxis is possible to occur in skin test- and specific IgE-negative patients. The contact system is a plasma protease cascade initiated by activation of factor XII (FXII). Many agents with negative ion surface can activate FXII to drive contact system. Our data showed that penicillin significantly induced hypothermia in propranolol- or pertussis toxin-pretreated mice. It also caused a rapid and reversible drop in rat blood pressure, which did not overlap with IgE-mediated hypotension. These effects could be countered by a bradykinin-B2 receptor antagonist icatibant, and consistently, penicillin indeed increased rat plasma bradykinin. Moreover, penicillin not only directly activated contact system FXII-dependently, but also promoted bradykinin release in plasma incubated-human umbilical vein endothelial cells. In fact, besides penicillin, other beta-lactams also activated the contact system in vitro. Since the autoactivation of FXII can be affected by multiple-factors, plasma from different healthy individuals showed vastly different amidolytic activity in response to penicillin, suggesting the necessity of determining the potency of penicillin to induce individual plasma FXII activation. These results clarify that penicillin-initiated non-allergic anaphylaxis is attributed to contact system activation, which might bring more effective diagnosis options for predicting penicillin-induced fatal risk and avoiding costly and inappropriate treatment clinically.

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.

Controversies in Perioperative Antimicrobial Prophylaxis

Although clinical guidelines for antibiotic prophylaxis across a wide array of surgical procedures have been proposed by multidisciplinary groups of physicians and pharmacists, clinicians often deviate from recommendations. This is particularly true when recommendations are based on weak data or expert opinion. The goal of this review is to highlight certain common but controversial topics in perioperative prophylaxis and to focus on the data that does exist for the recommendations being made.

Results of Intradermal Skin Testing with Cefazolin according to a History of Hypersensitivity to Antibiotics

BACKGROUND

The relationship between cephalosporin hypersensitivity and a history of β-lactam hypersensitivity is unclear. We evaluated the usefulness of routine intradermal cefazolin skin testing and its relationship with the history of β-lactam hypersensitivity.

METHODS

The electronic medical records of patients who underwent intradermal cefazolin (0.3 mg/mL) skin testing without negative controls from January 2010 to January 2011 at Seoul National University Bundang Hospital were evaluated. The history of β-lactam hypersensitivity of the patients was taken. Immediate adverse reactions after cefazolin injection were evaluated by searching the electronic medical records for key words and reviewing consultation documents of allergy specialists or dermatologists. The medical records of the patients were reviewed by an allergist.

RESULTS

There were 13,153 cases of cefazolin skin testing over the 13-month study period. Among the 12,969 cases with negative skin test results, 8 had immediate hypersensitivity related to cefazolin (0.06%). The negative predictive value of cefazolin skin testing alone was 99.94%. The overall positivity rate of cefazolin skin tests was 1.4% (184/13,153). Of the cases with a history of allergy to β-lactams, 15% (6/40) showed a positive cefazolin skin test result compared to only 1.36% (178/13,113) of cases with no such history (P < 0.001) including some false-positive tests.

CONCLUSION

The results suggest that routine screening involving cefazolin skin testing without negative controls is not useful for all patients, but could be helpful for those with a history of β-lactam hypersensitivity, although a large prospective study is needed to confirm this.

Evaluation and Management of Penicillin Allergy: A Review

IMPORTANCE

β-Lactam antibiotics are among the safest and most effective antibiotics. Many patients report allergies to these drugs that limit their use, resulting in the use of broad-spectrum antibiotics that increase the risk for antimicrobial resistance and adverse events.

OBSERVATIONS

Approximately 10% of the US population has reported allergies to the β-lactam agent penicillin, with higher rates reported by older and hospitalized patients. Although many patients report that they are allergic to penicillin, clinically significant IgE-mediated or T lymphocyte-mediated penicillin hypersensitivity is uncommon (<5%). Currently, the rate of IgE-mediated penicillin allergies is decreasing, potentially due to a decreased use of parenteral penicillins, and because severe anaphylactic reactions to oral amoxicillin are rare. IgE-mediated penicillin allergy wanes over time, with 80% of patients becoming tolerant after a decade. Cross-reactivity between penicillin and cephalosporin drugs occurs in about 2% of cases, less than the 8% reported previously. Some patients have a medical history that suggests they are at a low risk for developing an allergic reaction to penicillin. Low-risk histories include patients having isolated nonallergic symptoms, such as gastrointestinal symptoms, or patients solely with a family history of a penicillin allergy, symptoms of pruritus without rash, or remote (>10 years) unknown reactions without features suggestive of an IgE-mediated reaction. A moderate-risk history includes urticaria or other pruritic rashes and reactions with features of IgE-mediated reactions. A high-risk history includes patients who have had anaphylaxis, positive penicillin skin testing, recurrent penicillin reactions, or hypersensitivities to multiple β-lactam antibiotics. The goals of antimicrobial stewardship are undermined when reported allergy to penicillin leads to the use of broad-spectrum antibiotics that increase the risk for antimicrobial resistance, including increased risk of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. Broad-spectrum antimicrobial agents also increase the risk of developing Clostridium difficile (also known as Clostridioides difficile) infection. Direct amoxicillin challenge is appropriate for patients with low-risk allergy histories. Moderate-risk patients can be evaluated with penicillin skin testing, which carries a negative predictive value that exceeds 95% and approaches 100% when combined with amoxicillin challenge. Clinicians performing penicillin allergy evaluation need to identify what methods are supported by their available resources.

CONCLUSIONS AND RELEVANCE

Many patients report they are allergic to penicillin but few have clinically significant reactions. Evaluation of penicillin allergy before deciding not to use penicillin or other β-lactam antibiotics is an important tool for antimicrobial stewardship.

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.

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.

Improving Aztreonam Stewardship and Cost Through a Penicillin Allergy Testing Clinical Guideline

Background

Patients reporting penicillin allergy often receive unnecessary and costly broad-spectrum alternatives such as aztreonam with negative consequences. Penicillin allergy testing improves antimicrobial therapy but is not broadly used in hospitals due to insufficient testing resources and short-term expenses. We describe a clinical decision support (CDS) tool promoting pharmacist-administered penicillin allergy testing in patients receiving aztreonam and its benefits toward antimicrobial stewardship and costs.

Methods

A CDS tool was incorporated into the electronic medical record, directing providers to order penicillin allergy testing for patients receiving aztreonam. An allergy-trained pharmacist reviewed orders placed through this new guideline and performed skin testing and oral challenges to determine whether these patients could safely take penicillin. Data on tests performed, antibiotic utilization, and cost-savings were compared with patients tested outside the new guideline as part of our institution's standard stewardship program.

Results

The guideline significantly increased penicillin allergy testing among patients receiving aztreonam from 24% to 85% (P < .001) while reducing the median delay between admission and testing completion from 3.31 to 1.05 days (P = 0.008). Patients tested under the guideline saw a 58% increase in penicillin exposure (P = .046). Institutional aztreonam administration declined from 2.54 to 1.47 administrations per 1000 patient-days (P = .016). Average antibiotic costs per patient tested before and after CDS decreased from $1265.81 to $592.08 USD, a 53% savings.

Conclusions

Targeting penicillin allergy testing to patients on aztreonam yields therapeutic and economic benefits during a single admission. This provides a cost-effective model for inpatient testing.

Addressing Inpatient Beta-Lactam Allergies: A Multihospital Implementation

Addressing inaccurate penicillin allergies is encouraged as part of antibiotic stewardship in the inpatient setting. However, implementing interventions targeted at the 10% to 15% of inpatients reporting a previous penicillin allergy can pose substantial logistic challenges. We implemented a computerized guideline for patients with reported beta-lactam allergy at 5 hospitals within a single health care system in the Boston area. In this article, we describe our implementation roadmap, including both successes achieved and challenges faced. We explain key implementation steps, including assembling a team, stakeholder engagement, developing or selecting an approach, spreading the change, establishing measures, and measuring impact. The objective was to detail the lessons learned while empowering others to be part of this important, multidisciplinary work to improve the care of patients with reported beta-lactam allergies.

Evaluation of Penicillin Allergy in the Hospitalized Patient: Opportunities for Antimicrobial Stewardship

PURPOSE OF REVIEW

Penicillin allergy is often misdiagnosed and is associated with adverse consequences, but testing is infrequently done in the hospital setting. This article reviews historical and contemporary innovations in inpatient penicillin allergy testing and its impact on antimicrobial stewardship.

RECENT FINDINGS

Adoption of the electronic medical record allows rapid identification of admitted patients carrying a penicillin allergy diagnosis. Collaboration with clinical pharmacists and the development of computerized clinical guidelines facilitates increased testing and appropriate use of penicillin and related β-lactams. Education of patients and their outpatient providers is the key to retaining the benefits of penicillin allergy de-labeling. Penicillin allergy testing is feasible in the hospital and offers tangible benefits towards antimicrobial stewardship. Allergists should take the lead in this endeavor and work towards overcoming personnel limitations by partnering with other health care providers and incorporating technology that improves the efficiency of allergy evaluation.

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.

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.

Antimicrobial Stewardship Approaches in the Intensive Care Unit

Antimicrobial stewardship programs aim to monitor, improve, and measure responsible antibiotic use. The intensive care unit (ICU), with its critically ill patients and prevalence of multiple drug-resistant pathogens, presents unique challenges. This article reviews approaches to stewardship with application to the ICU, including the value of diagnostics, principles of empirical and definitive therapy, and measures of effectiveness. There is good evidence that antimicrobial stewardship results in more appropriate antimicrobial use, shorter therapy durations, and lower resistance rates. Data demonstrating hard clinical outcomes, such as adverse events and mortality, are more limited but encouraging; further studies are needed.

The Effect of Penicillin Allergy Testing on Future Health Care Utilization: A Matched Cohort Study

BACKGROUND

The effect that penicillin allergy testing has on future health care utilization is uncertain.

OBJECTIVE

Determine whether penicillin allergy testing affects future overall health care utilization as measured by outpatient department (OPD) visits, emergency department (ED) visits, and hospital days.

METHODS

Potential cases and control subjects were penicillin allergic Kaiser Permanente Southern California members who had at least 2 visits between 2010 and 2012 and at least 1 year of continuous health plan coverage before their index visit.

RESULTS

It was possible to match 308 (73.2%) of the potential cases to 1251 unique controls, on the basis of age, sex, weighted Charlson comorbidity index, drug class allergies, OPD visits, ED visits, and hospital days during the years before their index visit. Cases and controls were then followed for an average of 3.6 and 4.0 years, respectively. Based on results analyzed using a generalized linear mixed model, cases were estimated to have 0.09 fewer OPD visits (P < .001), 0.13 fewer ED visits (P = .29), and 0.55 fewer hospital days (P < .001) per health plan coverage year during follow-up compared with controls. Cases were exposed to more penicillins and first- and second-generation cephalosporins and less clindamycin and macrolides.

CONCLUSIONS

Penicillin allergy testing, primarily done in the setting of an outpatient Allergy consultation, was associated with significantly less health care utilization during 3.6+ years of follow-up and greater use of narrow-spectrum antibiotics. Penicillin allergy testing has a favorable cost-benefit ratio for the incremental cost of testing versus future health care utilization and improves antibiotic stewardship.

Tackling inpatient penicillin allergies: Assessing tools for antimicrobial stewardship

BACKGROUND

Reported penicillin allergy rarely reflects penicillin intolerance. Failure to address inpatient penicillin allergies results in more broad-spectrum antibiotic use, treatment failures, and adverse drug events.

OBJECTIVE

We aimed to determine the optimal approach to penicillin allergies among medical inpatients.

METHODS

We evaluated internal medicine inpatients reporting penicillin allergy in 3 periods: (1) standard of care (SOC), (2) penicillin skin testing (ST), and (3) computerized guideline application with decision support (APP). The primary outcome was use of a penicillin or cephalosporin, comparing interventions to SOC using multivariable logistic regression.

RESULTS

There were 625 patients: SOC, 148; ST, 278; and APP, 199. Of 278 ST patients, 179 (64%) were skin test eligible; 43 (24%) received testing and none were allergic. In the APP period, there were 292 unique Web site views; 112 users (38%) completed clinical decision support. Although ST period patients did not have increased odds of penicillin or cephalosporin use overall (adjusted odds ratio [aOR] 1.3; 95% CI, 0.8-2.0), we observed significant increased odds of penicillin or cephalosporin use overall in the APP period (aOR, 1.8; 95% CI, 1.1-2.9) and in a per-protocol analysis of the skin tested subset (aOR, 5.7; 95% CI, 2.6-12.5).

CONCLUSIONS

Both APP and ST-when completed-increased the use of penicillin and cephalosporin antibiotics among inpatients reporting penicillin allergy. While the skin tested subset showed an almost 6-fold impact, the computerized guideline significantly increased penicillin or cephalosporin use overall nearly 2-fold and was readily implemented.

A Proactive Approach to Penicillin Allergy Testing in Hospitalized Patients

BACKGROUND

Penicillin allergy testing is underutilized in inpatients despite its potential to immediately impact antibiotic treatment. Although most tested patients are able to tolerate penicillin, limited availability and awareness of this tool leads to the use of costly and harmful substitutes.

OBJECTIVE

We established an inpatient service at a large academic hospital to identify and test patients with a history of penicillin allergy with the goals of removing inaccurate diagnoses, reducing the use of beta-lactam alternatives, and educating patients and clinicians about the procedure.

METHODS

Eligible inpatients were flagged daily through the electronic medical record and prioritized via a specialized algorithm. A trained clinical pharmacist performed penicillin skin tests and challenges preemptively or by provider request. Clinical characteristics and antibiotic use were analyzed in tested patients.

RESULTS

A total of 1203 applicable charts were detected by our system leading to 252 direct evaluations over 18 months. Overall, 228 subjects (90.5%) had their penicillin allergy removed. Of these, 223 were cleared via testing and 5 by discovery of prior penicillin tolerance. Among patients testing negative, 85 (38%) subsequently received beta-lactams, preventing 504 inpatient days and 648 outpatient days on alternative agents.

CONCLUSIONS

Penicillin allergy testing using a physician-pharmacist team model effectively removes reported allergies in hospitalized patients. The electronic medical record is a valuable asset for locating and stratifying individuals who benefit most from intervention. Proactive testing substantially reduces unnecessary inpatient and outpatient use of beta-lactam alternatives that may otherwise go unaddressed.

Involvement of Histamine and RhoA/ROCK in Penicillin Immediate Hypersensitivity Reactions

The mechanism of penicillin immediate hypersensitivity reactions has not been completely elucidated. These reactions are generally considered to be mediated by IgE, but penicillin-specific IgE could not be detected in most cases. This study demonstrated that penicillin was able to cause vascular hyperpermeability in a mouse model mimicking clinical symptoms of penicillin immediate hypersensitivity reactions. The first exposure to penicillin also induced immediate edema and exudative reactions in ears and lungs of mice in a dose-dependent manner. Vasodilation was noted in microvessels in ears. These reactions were unlikely to be immune-mediated reactions, because no penicillin-specific IgE was produced. Furthermore, penicillin treatment directly elicited rapid histamine release. Penicillin also led to F-actin reorganization in human umbilical vein endothelial cells and increased the permeability of the endothelial monolayer. Activation of the RhoA/ROCK signaling pathway was observed in ears and lungs of mice and in endothelial cells after treatment with penicillin. Both an anti-histamine agent and a ROCK inhibitor attenuated penicillin immediate hypersensitivity reactions in mice. This study presents a novel mechanism of penicillin immediate hypersensitivity reactions and suggests a potential preventive approach against these reactions.

The Impact of Reporting a Prior Penicillin Allergy on the Treatment of Methicillin-Sensitive Staphylococcus aureus Bacteremia

Background

Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a morbid infection with mortality benefit from receipt of parenteral β-lactam therapy. A substantial portion of MSSA bacteremia patients report penicillin allergy, but infrequently have true allergy.

Objective

To determine the frequency and predictors of optimal and adequate therapy in patients with MSSA bacteremia.

Design

Retrospective cohort.

Participants

Adult inpatients with MSSA bacteremia, January 2009 through October 2013.

Main Measures

The primary measure was a trial of optimal therapy (OT), defined as ≥3 inpatient days or discharge on any first-line agents (nafcillin, oxacillin, cefazolin, or penicillin G, if susceptible). The secondary measure was completion of adequate therapy (AT), defined as ≥10 inpatient days or discharge on an agent appropriate for MSSA bacteremia. Data were electronically gathered with key variables manually validated through chart review. Log-binomial regression models were used to determine the frequency and predictors of outcomes.

Key Results

Of 456 patients, 346 (76%) received a trial of OT. Patients reporting penicillin allergy (13%) were less likely to receive OT trial than those without penicillin allergy (47% vs. 80%, p <0.001). Adjusting for other factors, penicillin allergy was the largest negative predictor of OT trial (RR 0.64 [0.49, 0.83]). Infectious Disease (ID) consultation was the largest positive predictor of OT trial across all patients (RR 1.34 [1.14, 1.57]). Allergy/Immunology consultation was the single most important predictor of OT trial among patients reporting penicillin allergy (RR 2.33 [1.44, 3.77]). Of 440 patients, 391 (89%) completed AT, with ID consultation the largest positive predictor of the outcome (RR 1.28 [1.15, 1.43]).

Conclusions

Nearly 25% of patients with MSSA bacteremia did not receive OT trial and about 10% did not receive AT completion. Reported penicillin allergy reduced, and ID consult increased, the likelihood of OT. Allergy evaluation, coupled with ID consultation, may improve outcomes in MSSA bacteremic patients.

Antimicrobial allergy 'labels' drive inappropriate antimicrobial prescribing: lessons for stewardship

BACKGROUND

The presence of antimicrobial allergy designations ('labels') often substantially reduces prescribing options for affected patients, but the frequency, accuracy and impacts of such labels are unknown.

METHODS

The National Antimicrobial Prescribing Survey (NAPS) is an annual de-identified point prevalence audit of Australian inpatient antimicrobial prescribing using standardized definitions of guideline compliance, appropriateness and indications. Data were extracted for 2 years (2013-14) and compared for patients with an antimicrobial allergy label (AAL) and with no AAL (NAAL).

RESULTS

Among 21 031 patients receiving antimicrobials (33 421 prescriptions), an AAL was recorded in 18%, with inappropriate antimicrobial use significantly higher in the AAL group versus the NAAL group (OR 1.12, 95% CI 1.05-1.22, P < 0.002). Patterns of antimicrobial use were significantly influenced by AAL, with lower β-lactam use (AAL versus NAAL; OR 0.47, 95% CI 0.43-0.50, P < 0.001) and higher quinolone (OR 2.07, 95% CI 1.83-2.34, P < 0.0001), glycopeptide (OR 1.59, 95% CI 1.38-1.83, P < 0.0001) and carbapenem (OR 1.74, 95% CI 1.43-2.13, P < 0.0001) use. In particular, among immunocompromised patients, AAL was associated with increased rates of inappropriate antimicrobial use (OR 1.68, 95% CI 1.21-2.30, P = 0.003), as well as increased use of quinolones (OR 1.88, 95% CI 1.16-3.03, P = 0.02) and glycopeptides (OR 1.82, 95% CI 1.17-2.84, P = 0.01).

CONCLUSIONS

AALs are common and appear to be associated with higher rates of inappropriate prescribing and increased use of broad-spectrum antimicrobials. Improved accuracy in defining AALs is likely to be important for effective antimicrobial stewardship (AMS), with efforts to 'de-label' inappropriate AAL patients a worthwhile feature of future AMS initiatives.

Impact of a clinical guideline for prescribing antibiotics to inpatients reporting penicillin or cephalosporin allergy

BACKGROUND

Self-reported penicillin allergy infrequently reflects an inability to tolerate penicillins. Inpatients reporting penicillin allergy receive alternative antibiotics that might be broader spectrum, more toxic, or less effective.

OBJECTIVE

To develop and assess a clinical guideline for the general inpatient provider that directs taking a history and prescribing antibiotics for patients with penicillin or cephalosporin allergy.

METHODS

A guideline was implemented to assist providers with assessing allergy history and prescribing antibiotics for patients with reported penicillin or cephalosporin allergy. The guideline used a standard 2-step graded challenge or test dose. A quasi-experimental study was performed to assess safety, feasibility, and impact on antibiotic use by comparing treatment 21 months before guideline implementation with 12 months after guideline implementation.

RESULTS

Significantly more test doses to β-lactam antibiotics were performed monthly after vs before guideline implementation (median 14.5, interquartile range 13-16.25, vs 2, interquartile range 1-3.25, P < .001). Seven adverse drug reactions occurred during guideline-driven test doses, with no significant difference in rate (3.9% vs 6.1%, P = .44) or severity (P > .5) between periods. Guideline-driven test doses decreased alternative antimicrobial therapy after the test dose, including vancomycin (68.3% vs 37.2%, P < .001), aztreonam (11.5% vs 0.5%, P < .001), aminoglycosides (6.0% vs 1.1%, P = .004), and fluoro quinolones (15.3% vs 3.3%, P < .001).

CONCLUSION

The implementation of an inpatient antibiotic prescribing guideline for patients with penicillin or cephalosporin allergy was associated with an almost 7-fold increase in the number of test doses to β-lactams without increased adverse drug reactions. Patients assessed with guideline-driven test doses were observed to have significantly decreased alternative antibiotic exposure.

Improving Clinical Outcomes in Patients With Methicillin-Sensitive Staphylococcus aureus Bacteremia and Reported Penicillin Allergy

BACKGROUND

Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a morbid infection. First-line MSSA therapies (nafcillin, oxacillin, cefazolin) are generally avoided in the 10% of patients reporting penicillin (PCN) allergy, but most of these patients are not truly allergic. We used a decision tree with sensitivity analyses to determine the optimal evaluation and treatment for patients with MSSA bacteremia and reported PCN allergy.

METHODS

Our model simulates 3 strategies: (1) no allergy evaluation, give vancomycin (Vanc); (2) allergy history-guided treatment: if history excludes anaphylactic features, give cefazolin (Hx-Cefaz); and (3) complete allergy evaluation with history-appropriate PCN skin testing: if skin test negative, give cefazolin (ST-Cefaz). Model outcomes included 12-week MSSA cure, recurrence, and death; allergic reactions including major, minor, and potentially iatrogenic; and adverse drug reactions.

RESULTS

Vanc results in the fewest patients achieving MSSA cure and the highest rate of recurrence (67.3%/14.8% vs 83.4%/9.3% for Hx-Cefaz and 84.5%/8.9% for ST-Cefaz) as well as the greatest frequency of allergic reactions (3.0% vs 2.4% for Hx-Cefaz and 1.7% for ST-Cefaz) and highest rates of adverse drug reactions (5.2% vs 4.6% for Hx-Cefaz and 4.7% for ST-Cefaz). Even in a "best case for Vanc" scenario, Vanc yields the poorest outcomes. ST-Cefaz is preferred to Hx-Cefaz although sensitive to input variations.

CONCLUSIONS

Patients with MSSA bacteremia and a reported PCN allergy should have the allergy addressed for optimal treatment. Full allergy evaluation with skin testing seems to be preferred, although more data are needed.

Factors associated with negative histamine control for penicillin allergy skin testing in the inpatient setting

BACKGROUND

Identification of factors adversely affecting the utility of allergy skin testing is important in optimizing patient care. Inpatient penicillin skin test data from 1997 through 2007 demonstrate that up to 20% of attempted penicillin skin tests are indeterminate owing to a negative histamine test response, despite exclusion of H1 antagonists. Critical illness, vasopressors, steroid use, and psychotropic medications have been postulated to influence outcomes, but large studies are lacking.

OBJECTIVE

To identify factors associated with a negative histamine test response for the inpatient setting.

METHODS

Fifty-two cases were identified with a negative histamine response after penicillin skin testing in the absence of antihistamine therapy for 72 hours before testing. One hundred twenty-five controls with a normal histamine response were randomly selected from same population. Independent variables assessed included stay in the intensive care unit (ICU), skin color, diabetes, age, use of vasopressors, H2 blocker, steroids, other immunosuppressive drugs, thyroid replacement, proton pump inhibitors, diuretics, 5 categories of psychotropic medications, and amiodarone.

RESULTS

Mean age was 68 years for cases vs 60 years for controls (P = .002). Bivariate analysis showed ICU stay was more frequent in cases than in controls (73.1% vs 33.6%, P < .001). Regression analysis yielded odds ratios (ORs) of 8.18 (95% confidence interval 3.22-20.76) for ICU status, 3.76 (1.30-10.92) for systemic corticosteroids, and 4.90 (1.17-20.62) for H2 blockers as associated with lack of histamine response. For every additional year in age, there was increase in the OR of 1.04 (1.01-1.07).

CONCLUSION

Regression analysis supports ICU stay during skin testing as associated with a high OR for a negative histamine response independent of age. Systemic corticosteroids, H2 blockers, and older age are associated with a significant OR for a negative histamine response. This is one of largest studies on factors associated with a negative histamine response for the inpatient setting and has significant implications for clinical practice.

Effect of a drug allergy educational program and antibiotic prescribing guideline on inpatient clinical providers' antibiotic prescribing knowledge

BACKGROUND

Inpatient providers have varying levels of knowledge in managing patients with drug and/or penicillin (PCN) allergy.

OBJECTIVES

Our objectives were (1) to survey inpatient providers to ascertain their baseline drug allergy knowledge and preparedness in caring for patients with PCN allergy, and (2) to assess the impact of an educational program paired with the implementation of a hospital-based clinical guideline.

METHODS

We electronically surveyed 521 inpatient providers at a tertiary care medical center at baseline and again 6 weeks after an educational initiative paired with clinical guideline implementation. The guideline informed providers on drug allergy history taking and antibiotic prescribing for inpatients with PCN or cephalosporin allergy.

RESULTS

Of 323 unique responders, 42% (95% CI, 37-48%) reported no prior education in drug allergy. When considering those who responded to both surveys (n = 213), we observed a significant increase in knowledge about PCN skin testing (35% vs 54%; P < .001) and loss of PCN allergy over time (54% vs 80%; P < .0001). Among those who reported attending an educational session (n = 62), preparedness to determine if an allergy was severe significantly improved (77% vs 92%; P = .03). Other areas, including understanding absolute contraindications to receiving a drug again and PCN cross-reactivity with other antimicrobials, did not improve significantly.

CONCLUSIONS

Inpatient providers have drug allergy knowledge deficits but are interested in tools to help them care for inpatients with drug allergies. Our educational initiative and hospital guideline implementation were associated with increased PCN allergy knowledge in several crucial areas. To improve care of inpatients with drug allergy, more research is needed to evaluate hospital policies and sustainable educational tools.

Health care use and serious infection prevalence associated with penicillin "allergy" in hospitalized patients: A cohort study

BACKGROUND

Penicillin is the most common drug "allergy" noted at hospital admission, although it is often inaccurate.

OBJECTIVE

We sought to determine total hospital days, antibiotic exposures, and the prevalence rates of Clostridium difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) in patients with and without penicillin "allergy" at hospital admission.

METHODS

We performed a retrospective, matched cohort study of subjects admitted to Kaiser Foundation hospitals in Southern California during 2010 through 2012.

RESULTS

It was possible to match 51,582 (99.6% of all possible cases) unique hospitalized subjects with penicillin "allergy" to 2 unique discharge diagnosis category-matched, sex-matched, age-matched, and date of admission-matched control subjects each. Cases with penicillin "allergy" averaged 0.59 (9.9%; 95% CI, 0.47-0.71) more total hospital days during 20.1 ± 10.5 months of follow-up compared with control subjects. Cases were treated with significantly more fluoroquinolones, clindamycin, and vancomycin (P < .0001) for each antibiotic compared with control subjects. Cases had 23.4% (95% CI, 15.6% to 31.7%) more C difficile, 14.1% (95% CI, 7.1% to 21.6%) more MRSA, and 30.1% (95% CI, 12.5% to 50.4%) more VRE infections than expected compared with control subjects.

CONCLUSIONS

A penicillin "allergy" history, although often inaccurate, is not a benign finding at hospital admission. Subjects with a penicillin "allergy" history spend significantly more time in the hospital. Subjects with a penicillin "allergy" history are exposed to significantly more antibiotics previously associated with C difficile and VRE. Drug "allergies" in general, but most those notably to penicillin, are associated with increased hospital use and increased C difficile, MRSA, and VRE prevalence.

The current practice of skin testing for antibiotics in Korean hospitals

BACKGROUND/AIMS

Antibiotic skin testing is a useful procedure for identifying patients with IgE-mediated hypersensitivity to antibiotics. The procedures, however, have not been standardized, and the testing is performed with diverse protocols in Korean hospitals wards. Thus, we examined the current practice of antibiotic skin testing in Korea.

METHODS

We sent questionnaires to 12 allergists working in secondary or tertiary referral hospitals and collected them by e-mail or fax. The questionnaire included items such as the types and concentrations of the tested antibiotics, the methods of antibiotic skin testing, and the interpretation of the results.

RESULTS

All hospitals responded to the questionnaire. The antibiotic skin testing protocols were variable, inconsistent, and differed with regard to the type and concentrations of antibiotics, the volume injected, and the interpretation of the results. Moreover, the protocols differed from the commonly recommended procedures in the medical literature.

CONCLUSIONS

Standardized guidelines for antibiotic skin testing are needed for the safe and effective use of antibiotics in Korea.

The use of penicillin skin testing to assess the prevalence of penicillin allergy in an emergency department setting

STUDY OBJECTIVE

Patient-reported penicillin allergies are often unreliable and can result in unnecessary changes in antibiotic therapy. Although penicillin allergy skin testing is commonly performed in allergy clinics, it has not been used in emergency departments (EDs) to verify self-reported allergies. We hypothesize that ED-based testing is possible and that the false-positive rate of patients with self-reported penicillin allergy are greater than 90%.

METHODS

This prospective observational cohort study enrolled a convenience sample of ED patients with a self-reported penicillin allergy. Patients were enrolled by one of 2 emergency physicians who performed skin prick and intracutaneous tests with penicillin major and minor determinants. The total testing time was 30 minutes. The proportion of false-positive self-reported allergies was computed with 95% confidence intervals (CIs) by using the score method.

RESULTS

A total of 150 patients (mean age 42 years; SD 16 years; 46% men; 47% black) were enrolled. The false-positive rate for self-reported penicillin allergy was 137 of 150 (91.3%; 95% CI 85.3% to 95.1%). There were no adverse reactions associated with penicillin skin testing. Compared with patients with a false-positive penicillin allergy result (confirmed by negative penicillin skin testing result), patients reporting a true penicillin allergy confirmed by positive penicillin skin test results tended to be more frequently men (61.5% versus 44.5%; Delta 17.0%; 95% CI -13.5% to 42%), black (69.2% versus 44.5%; Delta 24.7%; 95% CI -6.9% to 46.8%), and have no family history of drug allergy (7.7% versus 17.5%; Delta9.8%; 95% CI -20.9% to 20.4%), but self-reported other drug allergies more frequently (61.5% versus 38.7%; Delta 22.9%; 95% CI -7.7% to 47.5%).

CONCLUSION

Penicillin skin testing is feasible in the ED setting. A substantial number of patients who self-report a penicillin allergy do not exhibit immunoglobulin E-mediated sensitization to penicillin major and minor determinants. Penicillin testing in the ED may allow the use of more appropriate antibiotics for patients presenting with a history of penicillin allergy.

[Allergy to betalactams: myth and realities]

Allergic reactions to penicillins have been reported since the 1950s, shortly after their introduction as therapeutic agents. An increasing number of reported anaphylactic reactions and other adverse effects proved this to be a serious public health problem. Fifty years later, betalactam-induced hypersensitivity is the most frequent cause of drug reaction and has been the source of a great number of publications. Clinically, betalactam-induced allergic reactions may be immediate or non-immediate according to the time interval between drug intake and the occurrence of symptoms. The diagnosis of betalactam hypersensitivity is based on skin tests methods, in vitro tests and drug provocation test. There are three classical methods for skin testing: prick, intradermal, and patch. These tests are still the most sensitive techniques. In vitro tests, mainly based on the quantification of IgE antibodies to betalactams by immunoassay (Fluorescent Enzyme Immunoassay [FEIA]), may sometimes yield useful complementary information. Drug provocation tests must be performed with the required caution and the adequate indication. Algorithms are available for both immediate and non-immediate reactions to provide a practical approach for patient evaluation. They are based on the following data: clinical history, skin tests, FEIA, and drug provocation tests. Finally, cross reactivity between betalactams has been reported, especially between penicillins and cephalosporins. Their frequency was long over-estimated, but recent evidence, indicates that cross reactivity between betalactams has become rare. Administration of cephalosporins in patients with a history of penicillin allergy requires performing skin testing with penicillin, the probably allergenic drug, and the cephalosporin to be prescribed.

Penicillin skin testing in patients with a history of beta-lactam allergy

BACKGROUND

Vancomycin and fluoroquinolones are commonly used in patients with a history of penicillin allergy.

OBJECTIVE

To determine the safety and utility of penicillin skin testing (PST).

METHODS

Retrospective study of patients with a history of penicillin allergy between April 1, 1999, and September 30, 2004. Penicillin skin testing was performed by means of standard methods using benzylpenicilloyl-polysine, penicillin G, and histamine and saline controls.

RESULTS

Of 596 patients studied, 25.3% were outpatients, 50.3% were inpatients, and 24.3% were intensive care unit patients. The most common antibiotics used during the time of PST were vancomycin and fluoroquinolones. Results of PST were negative in 88.4% of patients, positive in 8.2%, and indeterminate in 3.4%. One patient (0.17%) developed urticaria immediately after PST. Fifty-five percent of patients with negative PST results were changed to a beta-lactam drug, more frequently in the intensive care unit vs the outpatient setting (70.3% vs 8.6%; P < .001) and in adults vs patients younger than 18 years (58.6% vs 8.1%; P < .001). A beta-lactam antibiotic was used in 290 patients with negative PST results. Of the patients given beta-lactam antibiotics, 5 (1.7%) had adverse reactions: 2 had hives after 16 and 20 days of therapy, 1 had a nonspecific rash after 17 days of therapy, 1 had flushing and urticaria 3 hours after a test dose of piperacillin-tazobactam, and 1 had a pruritic rash after 12 hours of therapy.

CONCLUSIONS

Patients with a history of penicillin allergy can safely use beta-lactam drugs if negative PST results.

The use of systemic antibiotics in the treatment of chronic wounds

The role of microorganisms in the etiology and persistence of chronic wounds remains poorly understood. The chronic wound bed houses a complex microenvironment that typically includes more than one bacterial species. Difficulty lies in determining when the presence of bacteria impedes wound healing, thereby warranting intervention. Indications for antibiotic therapy and optimal treatment regimens are ill defined. The goal of this article is to describe the appropriate role of systemic antibiotics in the management of chronic wounds. A common sense approach will be offered based on six clinically pertinent questions: Is infection present? Are systemic antibiotics necessary? Should treatment be enteral or parenteral? What antibiotic or combination of antibiotics should be used? What should be the duration of therapy? What special circumstances are present (i.e., concomitant illnesses, potential drug-drug interactions) that can impact therapy?

Clinical history as a predictor of penicillin skin test outcome

BACKGROUND

Up to 10% of the population reports an "allergy" to penicillin, whereas approximately 1.1% has positive penicillin skin test results. Where penicillin skin tests are unavailable, some have advocated using history to decide whether to use a penicillin-related antibiotic.

OBJECTIVE

To determine if clinical history predicts penicillin skin test results.

METHOD

Retrospective medical record review of 94 consecutive patients who had previously taken penicillin referred for penicillin allergy. Case histories were taken, penicillin skin tests performed, and an oral challenge recommended if skin test results were negative.

RESULTS

Of 91 cases studied, the average patient age was 27 years (range, 6 months to 82 years; 36% female). Fifty-two (57%) experienced hives as their main adverse reaction. Sixteen (18%) had at least 1 positive test result. Of this group, 9 had hives as their main symptom, whereas 1 had respiratory problems and 1 had angioedema. Most patients with positive skin test results had experienced their reaction at least 3 years ago. Regression analysis showed that age, sex, and clinical history, including type of reaction, time of reaction after penicillin ingestion, or time since the last reaction, were not associated with skin test positivity. Seventy-two (96%) of the 75 patients who had negative skin test results underwent oral challenge. Seventy had negative challenge results. The negative predictive value of a negative penicillin skin test result was 97%.

CONCLUSION

Clinical history was not predictive of subsequent penicillin skin test results.

Clinical outcomes of penicillin skin testing

BACKGROUND

Penicillin or cephalosporin allergy is a common problem with antibiotic drug prescribing in hospitalized patients.

OBJECTIVES

To study the various clinical outcomes of penicillin skin testing (PST) in a community teaching hospital and to determine the percentage of patients who have an antibiotic drug modification after PST.

METHODS

This study was a retrospective medical record review of all inpatients who underwent PST in 6.6 years. Information was collected on 101 patients using a detailed data collection form. Data were summarized using descriptive statistics, including frequencies and percentages.

RESULTS

Of the 101 patients who underwent PST, 92 had a negative result and 5 had a positive result; in 4 patients the test result was indeterminate. There was a 96% (67/70) reduction in the use of vancomycin and a 96% (23/24) reduction in the use of fluoroquinolones after PST in patients with negative results. Forty-nine percent of patients with negative PST results were administered a penicillin-based drug, and 48% were given a cephalosporin. Cultures were positive most commonly for Staphylococcus aureus and enterococcus. There were no serious adverse reactions to PST or to the use of penicillins or cephalosporins after a negative PST result.

CONCLUSIONS

Penicillin skin testing lowered the use of vancomycin and fluoroquinolones and increased the use of penicillin-based drugs and cephalosporins in patients with a history of beta-lactam drug allergies.

A rational approach to the evaluation and treatment of the infected patient in the intensive care unit

Critically ill patients are at increased risk of acquiring nosocomial infections. A thorough clinical evaluation and the selection of appropriate diagnostic techniques are important elements in the evaluation of these patients. Nonetheless, this selection process can be difficult because of the wide spectrum of disease that is seen in the ICU and the lack of standardized studies that have evaluated the different diagnostic methods that are available. Many different antimicrobials are available for the treatment of ICU-acquired infections. Most antimicrobial regimens have not been evaluated in large-scale, prospective, randomized trials. Until this information is available, the clinician must make an effort to be familiar with the different clinical and epidemiologic variables that can be used to stratify patients at the moment of selecting antimicrobial therapy. The information provided in this article, used in association with good clinical judgment, will help the critical care physician provide optimal initial management of the infected patient in the ICU.

A prospective observational study of the effect of penicillin skin testing on antibiotic use in the intensive care unit

BACKGROUND

Patients with penicillin allergy admitted to the intensive care unit (ICU) frequently receive non-beta-lactam antimicrobials for the treatment of infection. The use of these antimicrobials, more commonly vancomycin and fluoroquinolones, is associated with the emergence of multidrug-resistant infections. The penicillin skin test (PST) can help detect patients at risk of developing an immediate allergic reaction to penicillin and those patients with a negative PST may be able to use a penicillin antibiotic safely.

METHODS

We determined the incidence of true penicillin allergy, the percentage of patients changed to a beta-lactam antimicrobial when the test was negative, the safety of the test, and the safety of administration of beta-lactam antimicrobials in patients with a negative test. Skin testing was performed using standard methodology.

RESULTS

One hundred patients admitted to 4 ICUs were prospectively studied; 58 of them were male. The mean age was 63 years. Ninety-six patients had the PST: one was positive (1.04%), 10 (10.4%) were nondiagnostic, and 85 (88.5%) were negative. Of the 38 patients who received antimicrobials for therapeutic reasons, 31(81.5%) had the antibiotic changed to a beta-lactam antimicrobial after a negative reading versus 7 patients of the 57 (12%) who had received a prophylactic antimicrobial (P < .001). No adverse effects were reported after the PST or after antimicrobial administration.

CONCLUSIONS

The PST is a safe, reliable, and effective strategy to reduce the use of non-beta-lactam antimicrobials in patients who are labeled as penicillin allergic and admitted to the ICU.

The economic burden of antibiotic treatment of penicillin-allergic patients in internal medicine wards of a general tertiary care hospital

BACKGROUND

Penicillin allergy poses a major problem in the management of infectious diseases.

OBJECTIVE

We estimated the costs and usage of antibiotic treatment of 'penicillin-allergic' patients in comparison to non-allergic patients in a tertiary care hospital.

MATERIALS AND METHODS

The study was based on the records of 118 randomly chosen in-hospital patients labelled as being 'allergic to penicillin' and who were treated with antibiotics. The antibiotic selection and cost of the patients with alleged penicillin allergy were compared to 118 matched patients without an antibiotic allergy (controls).

RESULTS

During in-hospital treatment, the mean antibiotic cost for penicillin-allergic patients was 63% higher than the cost for the controls. In addition, there was a 38% higher cost of the recommended anti-microbial treatment regimen to be followed upon discharge by the former compared to the latter.

CONCLUSIONS

Penicillin-allergic patients were more likely to receive broader spectrum antibiotics compared to the non-allergic ones. Since many of the patients who are labelled as being 'allergic to penicillin' are, in fact, not allergic to it, inaccurate reporting of penicillin allergies may have costly economic and epidemiologic repercussions in addition to more toxic effects which can occur when choosing alternative drugs in case of penicillin allergy.