Adverse reactions during drug challenges: a single US institution's experience

United States Drug Allergy Registry (USDAR) grading scale for immediate drug reactions

BACKGROUND

There is no accepted grading system classifying the severity of immediate reactions to drugs.

OBJECTIVE

The purpose of this article is to present a proposed grading system developed through the consensus of drug allergy experts from the United States Drug Allergy Registry (USDAR) Consortium.

METHODS

The USDAR investigators sought to develop a consensus severity grading system for immediate drug reactions that is applicable to clinical care and research.

RESULTS

The USDAR grading scale scores severity levels on a scale of 0 to 4. A grade of no reaction (NR) is used for patients who undergo challenge without any symptoms or signs, and it would confirm a negative challenge result. A grade 0 reaction is indicative of primarily subjective complaints that are commonly seen with both historical drug reactions and during drug challenges, and it would suggest a low likelihood of a true drug allergic reaction. Grades 1 to 4 meet the criteria for a positive challenge result and may be considered indicative of a drug allergy. Grade 1 reactions are suggestive of a potential immediate drug reaction with mild symptoms. Grade 2 reactions are more likely to be immediate drug reactions of moderate severity. Grade 3 reactions have features suggestive of a severe allergic reaction, whereas grade 4 reactions are life-threatening reactions such as anaphylactic shock and fatal anaphylaxis.

CONCLUSION

This proposed grading schema for immediate drug reactions improves on prior schemata by being developed specifically for immediate drug reactions and being easy to implement in clinical and research practice.

Drug allergy in older adults: A study from the United States Drug Allergy Registry

BACKGROUND

Older adults have an increased risk of adverse drug reactions and negative effects associated with alternative antibiotic use. Although the number of antibiotic allergies reported increases with age, the characteristics and outcomes of older adults receiving drug allergy assessment are unknown.

OBJECTIVE

To assess the characteristics and outcomes of drug allergy evaluations in older adults.

METHODS

We considered patients aged above or equal to 65 years enrolled in the United States Drug Allergy Registry (USDAR), a US multisite prospective cohort (January 16, 2019 to February 28, 2022). Data were summarized using descriptive statistics.

RESULTS

Of 1678 USDAR participants from 5 sites, 406 older adults aged above or equal to 65 years (37% 65-69 years, 37% 70-74 years, 16% 75-79 years, and 10% ≥80 years) received 501 drug allergy assessments. USDAR older adults were primarily of female sex (69%), White (94%), and non-Hispanic (98%). Most USDAR older adults reported less than or equal to 1 infections per year (64%) and rated their general health as good, very good, or excellent (80%). Of 296 (59%) penicillin allergy assessments in USDAR older adults, 286 (97%) were disproved. Other drug allergy assessments included sulfonamide (n = 41, 88% disproved) and cephalosporin (n = 20, 95% disproved) antibiotics. All 41 drug allergy labels in USDAR participants aged above or equal to 80 years and all 80 penicillin allergy labels in USDAR men aged above or equal to 65 years were disproved.

CONCLUSION

Older adults represented a quarter of USDAR participants but were neither racially nor ethnically diverse and were generally healthy without considerable antibiotic need. Most older adults presented for antibiotic allergy assessments, the vast majority of which were disproved. Drug allergy assessments may be underutilized in the older adults who are most vulnerable to the harms of unconfirmed antibiotic allergy labels.

Drug provocation tests in children: All that glitters is not gold

A proper allergy work-up, based on the gold standard drug provocation test (DPT), usually rules out suspected drug hypersensitivity in children. These tests are generally open, given their high efficiency compared with double-blind placebo-controlled DPTs. Although their negative predictive value is excellent, no studies have calculated their positive predictive value, highly dependent on the prevalence of the disease. Most studies have found a rate of <5%-10% of true beta-lactam hypersensitivity in children. Given this low prevalence (pre-test probability), a few false-positive results can significantly reduce the estimated positive predictive value. False positives may arise from the nocebo effect during the test, including nocebo by proxy, or from observer bias, which depends on professional expertise and organizational circumstances. Some studies have found a high rate of tolerance on a second DPT in children who failed the first, but these results may be affected by the interval between the two tests, of a year or more in most cases, reflecting a loss of hypersensitivity over time. Taking into account the low rate of positive DPTs, with commonly mild reactions, we suggest confirming nonsevere positive DPTs with a second provocation performed soon after the first, especially in the case of beta-lactam antibiotics, in order to improve the diagnostic accuracy, de-label more patients, and achieve a better estimation of true drug hypersensitivity prevalence. In case of mild immediate reactions, the potential benefits of a second DPT should be carefully weighed against the risk of anaphylaxis.

Improving drug allergy label accuracy by supervised safety- and protocol-driven evaluation

Introduction: Drug allergies are often self-reported but of unknown accuracy. We carried out a prospective study to examine the utility and safety of formal allergology evaluation, and to identify factors associated with accurate drug allergy labels. Method: All patients who underwent drug allergy evaluation in our clinic during the study period were recruited. Baseline demographics, characteristics of index hypersensitivity reaction and outcomes of evaluation were recorded. Results: A total of 331 patients from March 2019 to June 2021 completed drug allergy evaluation to index drugs of concern. There were 123 (37%) male patients, and the mean age was 49 years (standard deviation 17). There were 170 beta-lactam antibiotics, 53 peri-operative drugs, 43 others, 38 non-steroidal anti-inflammatory drugs, and 27 non-beta-lactam antibiotic evaluations. Index reaction occurred within 5 years in 165 (50%) patients, with latency of less than 4 hours in 125 (38%) patients. The most common index reactions were rash, angioedema and urticaria. There were 57 (17%) evaluations stratified as low risk, 222 (67%) moderate risk, and 52 (16%) high risk based on multidisciplinary consensus. Allergy label was found to be false (negative drug evaluation) in 248 (75%) patients, while 16/237 (7%) skin tests, 44/331 (13%) in-clinic graded challenge, and 23/134 (17%) home prolonged challenges were positive (true drug allergy). The most common evaluation reactions were rash and urticaria. No cases of anaphylaxis were elicited. Conclusion: Seventy-five percent of drug allergy labels are inaccurate. Risk-stratified, protocolised allergy evaluation is safe. Prolonged drug challenge increases the sensitivity of drug allergy evaluation and should therefore be performed when indicated. Keywords: Drug allergy, drug hypersensitivity, graded challenge, prolonged drug provocation, skin testing

Frequency of severe reactions following penicillin drug provocation tests: A Bayesian meta-analysis

BACKGROUND

Patients with a penicillin allergy label tend to have worse clinical outcomes and increased healthcare use. Drug provocation tests (DPT) are the gold-standard in the diagnostic workup of penicillin allergy, but safety concerns may hinder their performance. We aimed to assess the frequency of severe reactions following a DPT in patients with reported allergy to penicillins or other β-lactams.

METHODS

We performed a systematic review, searching MEDLINE, Scopus, and Web of Science. We included primary studies assessing participants with a penicillin allergy label who underwent a DPT. We performed a Bayesian meta-analysis to estimate the pooled frequency of severe reactions to penicillin DPTs. Sources of heterogeneity were explored by subgroup and metaregression analyses.

RESULTS

We included 112 primary studies which included a total of 26,595 participants. The pooled frequency of severe reactions was estimated at 0.06% (95% credible interval [95% CrI] = 0.01%-0.13%; I2  = 57.9%). Most severe reactions (80/93; 86.0%) consisted of anaphylaxis. Compared to studies where the index reaction was immediate, we observed a lower frequency of severe reactions for studies assessing non-immediate index reactions (OR = 0.05; 95% CrI = 0-0.31). Patients reporting anaphylaxis as their index reaction were found to be at increased risk of developing severe reactions (OR = 13.5; 95% CrI = 7.7-21.5; I2  = 0.3%). Performance of direct DPTs in low-risk patients or testing with the suspected culprit drug were not associated with clinically relevant increased risk of severe reactions.

CONCLUSIONS

In patients with a penicillin allergy label, severe reactions resulting from DPTs are rare. Therefore, except for patients with potentially life-threatening index reactions or patients with positive skin tests-who were mostly not assessed in this analysis -, the safety of DPTs supports their performance in the diagnostic assessment of penicillin allergy.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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.

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.

The Cost of Penicillin Allergy Evaluation

BACKGROUND

Unverified penicillin allergy leads to adverse downstream clinical and economic sequelae. Penicillin allergy evaluation can be used to identify true, IgE-mediated allergy.

OBJECTIVE

To estimate the cost of penicillin allergy evaluation using time-driven activity-based costing (TDABC).

METHODS

We implemented TDABC throughout the care pathway for 30 outpatients presenting for penicillin allergy evaluation. The base-case evaluation included penicillin skin testing and a 1-step amoxicillin drug challenge, performed by an allergist. We varied assumptions about the provider type, clinical setting, procedure type, and personnel timing.

RESULTS

The base-case penicillin allergy evaluation costs $220 in 2016 US dollars: $98 for personnel, $119 for consumables, and $3 for space. In sensitivity analyses, lower cost estimates were achieved when only a drug challenge was performed (ie, no skin test, $84) and a nurse practitioner provider was used ($170). Adjusting for the probability of anaphylaxis did not result in a changed estimate ($220); although other analyses led to modest changes in the TDABC estimate ($214-$246), higher estimates were identified with changing to a low-demand practice setting ($268), a 50% increase in personnel times ($269), and including clinician documentation time ($288). In a least/most costly scenario analyses, the lowest TDABC estimate was $40 and the highest was $537.

CONCLUSIONS

Using TDABC, penicillin allergy evaluation costs $220; even with varied assumptions adjusting for operational challenges, clinical setting, and expanded testing, penicillin allergy evaluation still costs only about $540. This modest investment may be offset for patients treated with costly alternative antibiotics that also may result in adverse consequences.

Identifying Allergic Drug Reactions Through Placebo-Controlled Graded Challenges

BACKGROUND

Graded challenges are performed to exclude hypersensitivity reactions in patients with a low likelihood of drug allergy. Literature regarding optimal protocols with a defined number of steps and use of placebo is lacking.

OBJECTIVE

To identify allergic drug reactions (ADRs) through a 3-step protocol composed of placebo followed by a 2-step graded drug challenge.

METHODS

We performed a 5-year retrospective chart review of all patients with historical ADRs who underwent single-blind, placebo-controlled graded drug challenges between October 2010 and November 2015 at an outpatient drug allergy clinic. Patients' demographic characteristics and description of historical reaction were obtained. Outcomes of challenges to drug versus placebo were compared by drug class.

RESULTS

Two hundred twenty-nine patients underwent at least 1 single-blind placebo-controlled graded challenge. The most commonly challenged drug class was beta-lactams (70.8%) followed by nonsteroidal anti-inflammatory drugs (17.5%). The reaction rate to drug and placebo was similar during beta-lactam challenges (9.4% vs 8.2%; P = .9) and during nonsteroidal anti-inflammatory drug challenges (14% vs 7%, P = .5), respectively. Only 10 patients (4.4%) had objective findings during drug challenges. Patients who reacted to placebo before beta-lactam challenges had an increased number of drug allergies (4.3 ± 1.0) compared with nonreactors (2.4 ± 0.1) and to beta-lactam reactors (3.3 ± 0.7) (P = .002). All placebo reactors were female (20 of 183 vs 0 of 46 males; P = .02).

CONCLUSIONS

Two-step graded challenges are safe in appropriately selected patients with a low risk of reaction. Placebo should be considered to reduce false-positive results, especially in females and in patients with multiple drug allergies.

Molecularly imprinted polymers for the solid-phase extraction of four fluoroquilones from milk and lake water samples

A method based on molecular crowding and ionic liquids as reaction solvents has been used for the synthesis of molecularly imprinted polymers. Levofloxacin was selected as the template, polymethyl methacrylate was the molecular crowding agent, and 1-butyl-3-methylimidazolium tetrafluoroborate (ionic liquid) was selected as the reaction solvent and porogen. The optimized proportion for the mixed porogen was dimethyl sulfoxide/ionic liquid/polymethyl methacrylate 1:1.6:5 in chloroform (150 mg mL(-1) ). The morphology and chemical composition of levofloxacin imprinted polymers were assessed by scanning electron microscopy and Fourier transform infrared spectroscopy. The absorption experiments demonstrated that the levofloxacin imprinted polymers possess high selective recognition property to levofloxacin and analogs, including enrofloxacin, ciprofloxacin and gatifloxacin, which all belong to fluoroquinolones. An extraction method using levofloxacin imprinted polymers as sorbent followed by high-performance liquid chromatography analysis was optimized for the determination of four fluoroquinolones in milk and lake water samples. Under the optimized conditions, good linearity was observed in a range of 5-1000 ng g(-1) with the limit of detection between 0.3 and 0.5 ng g(-1) for the four fluoroquinolones. The recoveries at three spiked levels ranged 82.4-98.3% with the relative standard deviation ≤4.9.

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.

Anaphylaxis to drugs

Drug-induced anaphylaxis is a common cause of anaphylaxis and a leading cause of fatal anaphylaxis. Antibiotics, radiocontrast, and nonsteroidal anti-inflammatory drugs are commonly implicated drugs. Vocal cord dysfunction can mimic anaphylaxis and is often overlooked. β-Lactams are a common cause of anaphylaxis; however, skin testing and drug challenge can usually determine tolerability of other classes of β-lactams. Nonionic contrast agents cause anaphylaxis less frequently than ionic contrast, and immunoglobulin E-mediated mechanisms may have a role in some of these reactions. Skin testing with radiocontrast may have a role in evaluating patients with anaphylaxis to nonionic contrast.

Evaluation of antibiotic allergy: the role of skin tests and drug challenges

Antibiotic allergies are frequently reported in both adult and pediatric populations. While a detailed drug history is essential in the evaluation of antibiotic allergy, the history is typically insufficient to determine the presence of a drug allergy. The most readily available diagnostic testing for evaluating antibiotic allergies are drug skin testing and drug challenges. This review will focus on updates in the evaluation of antibiotic allergy utilizing immediate skin tests, delayed intradermal testing, drug patch tests, and drug challenges for both adults and children with histories of antibiotic allergies.