Prevalence and Characteristics of Antibiotic Allergy in Patients Over 65 Years in A Long-Term Care Setting

Antibiotic allergy is a commonly reported condition in clinical practice, particularly among older adults, who represent a growing segment of the population in long-term care facilities. The perception of antibiotic allergy, whether confirmed or suspected, has far-reaching implications for patient care. It can significantly impact treatment options, often leading to the avoidance of first-line antibiotics, such as beta-lactams, and the use of alternative agents that may be less effective, more toxic, or contribute to the development of antimicrobial resistance. In addition to complicating individual patient management, the mislabeling of antibiotic allergies can have broader consequences for antibiotic stewardship efforts, which aim to optimize antibiotic use and combat resistance. 

Older adults, particularly those in long-term care settings, are a uniquely vulnerable population when it comes to antibiotic allergies. They often have complex medical histories, with multiple comorbidities and frequent exposure to antibiotics, increasing the likelihood of adverse drug reactions. However, these reactions are not always true allergic responses and may instead represent side effects, drug intolerances, or immune-mediated events. Distinguishing true antibiotic allergies from these alternative explanations is critical to ensuring that patients receive the most effective and appropriate treatment. 

Despite the clinical importance of identifying true antibiotic allergies, allergological evaluations are not routinely performed in many cases. This lack of confirmatory testing results in many patients being labeled as allergic based solely on clinical suspicion or historical reports, without objective evidence. Such practices can lead to overdiagnosis of antibiotic allergy and unnecessary limitations in therapeutic options, especially in settings like long-term care facilities, where the prevalence of multidrug-resistant infections further complicates antibiotic selection. 

This study aimed to evaluate the prevalence and characteristics of suspected antibiotic allergies in patients aged 65 years and older residing at the Centro Sociosanitario Dolors Aleu in Barcelona. Specifically, we sought to determine the types of antibiotics most implicated, the frequency of allergological confirmation, and the role of clinical suspicion in reported cases. By addressing these questions, we hope to highlight the importance of systematic allergic evaluation in this population and its potential role in improving antibiotic stewardship and patient outcomes.

This pilot study was designed to evaluate the prevalence and characteristics of reported antibiotic allergies in elderly patients residing at the Centre Sociosanitari Colisée Dolors Aleu in Barcelona. The study population consisted of 100 patients aged 65 years and older, selected from the facility’s database based on their medical history availability and documented antibiotic use [1]. The study adhered to ethical standards for research involving human subjects and was approved by the relevant institutional review board. Data were collected retrospectively from the Electronic Medical Records (EMRs) of the participants. Information gathered included: Reported antibiotic allergies: The specific antibiotics identified as allergens in patient histories. Type of antibiotics implicated: Categorization of implicated antibiotics into beta-lactams (for example penicillins, sulfonamides, quinolones and others [2,3]. Allergological evaluation: Whether a formal diagnostic allergological study had been conducted or if the allergy was documented solely based on clinical suspicion. Adverse Drug Reactions (ADRs): Differentiation between confirmed allergic reactions and adverse drug events that were not subjected to diagnostic confirmation. Comorbidities: Associated medical conditions were recorded to understand their prevalence in the context of reported antibiotic allergies. 

Inclusion criteria: Patients were eligible for inclusion if they met the following criteria:

• Aged 65 years or older
• Resided at the Centre Sociosanitari Colisée Dolors Aleu 

Exclusion criteria: Patients with incomplete medical records or without documentation of antibiotic use or allergy history were excluded. 

Data analysis: The collected data were analyzed to determine:

• The overall prevalence of reported antibiotic allergies in the study population
• The distribution of implicated antibiotics, focusing on the frequency of beta-lactams, sulfonamides and quinolones
• The proportion of allergies confirmed through allergological testing compared to those based solely on clinical suspicion or adverse drug reactions
• The prevalence of comorbid conditions among patients with reported antibiotic allergies 

Statistical analysis involved descriptive methods, including percentages and frequencies, to compare the findings with existing literature on antibiotic allergies in similar populations. The study also explored potential associations between the presence of comorbidities and the likelihood of reported antibiotic allergies. 

• Ethical considerations

All data were anonymized to protect patient confidentiality. The study was conducted following the principles outlined in the Declaration of Helsinki. As the study relied on retrospective data, informed consent was not required, as approved by the ethics committee overseeing the research. This methodology provided a comprehensive framework to evaluate the burden of antibiotic allergies in an elderly population, setting the stage for further research to optimize antibiotic stewardship and clinical outcomes.

• Prevalence of antibiotic allergies 

The prevalence of reported antibiotic allergies in the study population was 18%. However, only 15% of reported allergies were confirmed through allergological evaluation. The vast majority (85%) were based on clinical suspicion or documentation of adverse drug reactions without formal testing (Figure 1). 

 Figure 1: Rate of confirmatory allergy testing.

• Antibiotics implicated 

Among the antibiotics implicated in reported allergies, beta-lactams represented the largest category, accounting for 67% of cases. Within this group:

• Penicillins were the most commonly implicated, making up 50% of all beta-lactam-associated allergies.
• Cephalosporins accounted for 12%.
• Carbapenems represented 5%.

Sulfonamides were the second most implicated group, responsible for 22% of reported allergies. All cases in this category were attributed to trimethoprim-sulfamethoxazole, a well-known allergenic agent. Quinolones accounted for 11% of reported allergies, with ciprofloxacin responsible for 7% and levofloxacin for 4% (Figure 2). 

 Figure 2: Prevalence of reported antibiotic allergies.

• Prevalence of other allergic conditions 

In addition to antibiotic allergies, other allergic diseases were identified in the study population, further highlighting an atopic predisposition among these patients (Figure 3) 

• Asthma: Reported in 10% of patients
• Rhinoconjunctivitis: Found in 8% of patients
• Food allergies: Documented in 5% of patients 

 Figure 3: Comorbidities and associated allergic conditions in the study population.

• Comorbidities 

Significant comorbidities were prevalent in the study population, reflecting the complex medical needs of elderly patients (Figure 3):

• Cardiovascular disease (75%): This included hypertension (40%), ischemic heart disease (20%), and atrial fibrillation (15%)
• Diabetes mellitus (42%): Among these patients, 35% had type 2 diabetes, and 7% had diabetic nephropathy
• Chronic kidney disease (31%): Renal impairment may complicate antibiotic management and increase the likelihood of adverse drug reactions being misinterpreted as allergies [4,5]

The results of this pilot study highlight significant challenges in the management of reported antibiotic allergies in elderly patients residing in long-term care facilities. The findings confirm that antibiotic allergy is a prevalent concern, with 18% of the study population labeled as allergic to at least one antibiotic. This prevalence aligns with previous reports in similar populations, underscoring the clinical importance of this issue. However, the striking finding that only 15% of reported allergies underwent allergic confirmation highlights a critical gap in clinical practice. Without confirmatory testing, most reported allergies (85%) are based on clinical suspicion or adverse drug reactions that may not represent true hypersensitivity. This overreliance on unverified reports can lead to the unnecessary avoidance of first-line antibiotics, such as beta-lactams, which are often critical for effective treatment. The predominance of beta-lactams (67%), particularly penicillins (50%), among implicated antibiotics further emphasizes the impact of these unconfirmed reports on antibiotic prescribing practices [6]. When first-line antibiotics are avoided due to unverified allergy reports, clinicians may resort to alternative agents. The reliance on these alternatives not only complicates treatment but may also contribute to antimicrobial resistance, a growing global health concern. 

The study also underscores the complex medical profiles of elderly patients reporting antibiotic allergies. The high prevalence of cardiovascular disease (75%), diabetes mellitus (42%), and chronic kidney disease (31%) reflects the significant burden of comorbidities in this population. These conditions can alter the pharmacokinetics and pharmacodynamics of antibiotics, increasing the likelihood of adverse drug reactions that may be misinterpreted as allergies. Additionally, the co-occurrence of other allergic conditions, such as asthma (10%), rhinoconjunctivitis (8%), and food allergies (5%), suggests an underlying atopic predisposition that may influence the reporting and diagnosis of antibiotic allergies [7-11]. 

The findings of this study highlight the need for a more systematic approach to managing antibiotic allergies in elderly patients. Incorporating allergological evaluations into routine care could help distinguish true allergies from adverse reactions or misdiagnoses. Such evaluations would enable the use of beta-lactams and other first-line antibiotics where appropriate, reducing the reliance on broader-spectrum agents and improving antibiotic stewardship. Furthermore, addressing the diagnostic gap could mitigate the risks associated with inappropriate prescribing, including treatment failures, resistance and adverse effects [12].

This study provides valuable insights into the prevalence and characteristics of reported antibiotic allergies in elderly patients and highlights significant diagnostic and therapeutic challenges. The key findings are as follows:

• The prevalence of reported antibiotic allergies in this population is consistent with rates observed in similar settings, with beta-lactams being the most implicated class of antibiotics
• Most reported allergies lack allergological confirmation, emphasizing the need for systematic diagnostic evaluations to guide clinical decision-making
• Comorbidities and co-occurring allergic conditions further complicate the management of antibiotic allergies, underscoring the importance of individualized care 

The findings underscore the urgent need for strategies to improve the diagnosis and management of antibiotic allergies in elderly patients. Future studies should focus on evaluating the clinical and economic impact of allergological evaluations in this population and exploring interventions to integrate such evaluations into routine care. By addressing these challenges, healthcare providers can enhance antibiotic stewardship, optimize patient outcomes, and reduce the burden of antibiotic resistance in long-term care settings.

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