Allergies to β-lactam antibiotics are among the most documented drug allergies, and approximately 10% of the US population reports an allergy specifically to penicillin.1,2 Many allergic reactions are mediated via the antibody immunoglobulin E (IgE), producing an immediate hypersensitivity response, such as hives or anaphylaxis, which can be life threatening. Reactions also may be mediated by T cells of the immune system, which target various cell lines and can cause a drug reaction with eosinophilia and systemic symptoms or Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN).3Although β-lactam and penicillin allergies are frequently reported, < 5% manifest as either an IgE or T-cell–mediated response.4Furthermore, for the small proportion of patients who once had a true IgE-mediated reaction, including anaphylaxis, 80% experience a decrease in IgE antibodies over time, resulting in a loss of allergic response after about 10 years.2 Due to this decline in IgE response and the initial mislabeling of mild non-IgE penicillin reactions, 95% of patients who are labeled as penicillin-allergic can eventually tolerate a penicillin.2
When a patient’s β-lactam allergy is never reevaluated, negative consequences can ensue. This allergy in a patient’s medical record can lead to the inappropriate avoidance of the entire β-lactam antibiotic class, which includes all penicillins, cephalosporins, and carbapenems. Withholding these antibiotics in certain situations can lead to negative patient outcomes.5-7 For example, the drugs of choice for the infections syphilis and methicillin-susceptible Staphylococcus aureus (S aureus) are a penicillin or cephalosporin, and patients labeled as penicillin-allergic are more likely to experience treatment failure from using second-line therapies.8 Additionally, receiving non-β-lactam antibiotics puts patients at risk of multidrug-resistant pathogens like methicillin-resistant S aureus and vancomycin-resistant Enterococcus (VRE) as well as adverse effects, such as Clostridioides difficile infection.9 Using alternative, and likely broad-spectrum, antibiotics also can be financially detrimental: These medications often are more costly than their β-lactam alternatives, and the inappropriate use of therapies can result in longer hospital courses.9-11
Penicillin allergies can complicate the antibiotic treatment strategy. The Memphis Veterans Affairs Medical Center (MVAMC) in Tennessee recently examined the negative sequelae of β-lactam allergies and found that more than half the patients received inappropriate antibiotics based on guideline recommendations, allergy history, and culture and sensitivity data.12 To mitigate the problems for patients with β-lactam allergies, the 2016 guidelines from the Infectious Diseases Society of America (IDSA) on the Implementation of Antimicrobial Stewardship Programs (ASP) recommend that these patients undergo allergy assessment and penicillin skin testing.13In November 2017, MVAMC implemented such a process. The purpose of this study was to describe our pharmacist-run β-lactam allergy assessment (BLAA) protocol and penicillin allergy clinic (PAC) and evaluate their overall outcomes: the proportion of patients who have been cleared to receive an alternative β-lactam antibiotic or who have had their allergy removed altogether.
Methods
We conducted a retrospective, observational study with approval from the institutional review board at MVAMC. This institution is an academic teaching center with 240 acute care beds and a variety of outpatient clinics available at the main campus, serving veterans in Memphis and the Mid-South area, including west Tennessee, northern Mississippi, and northeastern Arkansas. Patients were consecutively evaluated from November 2017 through February 2020. All MVAMC patients with a documented β-lactam allergy were eligible for inclusion; there were no exclusion criteria. Electronic health record data were assessed and included basic patient demographics, allergy history, and the outcome of the BLAA and PAC. Descriptive statistics were used for data analysis.
The purpose of the BLAA process is to evaluate, clarify, and potentially clear patients of their β-lactam allergies. Started in November 2017, the process includes appropriate patient screening with documentation of the β-lactam allergy. When patients with a β-lactam allergy are admitted to the hospital, they are interviewed by an inpatient CPS. This pharmacist then enters an assessment into the patient’s chart, which includes details of the allergen, reaction, and timing of the event. Based on this information, the CPS provides recommendations: clearance for alternative β-lactams, avoidance of all β-lactams, or removal of the allergy.
In January 2019, the pharmacist-driven penicillin allergy clinic (PAC) was started. Eligible patients receive a skin test to confirm or rule out their allergy after hospital discharge. To facilitate patient identification and screening, the ASP/infectious diseases (ID) clinical pharmacist runs a daily report of hospitalized patients with documented β-lactam allergies. All inpatient CPSs had access to this report and could easily identify and interview patients. Following the interview, the pharmacist enters a note in the patient’s chart, using the BLAA template (eFigures 1 and 2). On completion, a note is viewable in the Notes section adjacent to the patient’s allergies. The pharmacist then can enter a PAC consult for eligible patients. Although most patients qualify for PAC, exclusion criteria include non–IgE-mediated allergies (ie, SJS/TEN), allergies to β-lactams other than penicillins, or recent reactions (ie, within the past 5 years). Each inpatient CPS is trained on this BLAA process, which includes patient screening, chart review, patient interviewing, and the BLAA template and note completion. Pharmacists must demonstrate competency in completing 5 BLAA notes with review from the ASP/ID pharmacist. Once training is completed, this process is integrated into the pharmacist’s everyday workflow.
On receipt of the PAC consult, the ASP/ID pharmacist reviews the patient chart to further assess for eligibility and to determine whether oral challenge alone or skin testing followed by the oral challenge is required based on patient risk stratification (Table 1).3Relative contraindications to PAC include severe or unstable lung disease that requires home oxygen, frequent or recurrent heart failure exacerbations, or patients with acute or unstable cardiopulmonary, neurologic, or mental health conditions. These scenarios are discussed case by case with the allergy/immunology (A/I) physician.
The ASP/ID pharmacist also reviews the patient’s chart for medications that may blunt the histamine response during drug testing. The need to hold these medications before PAC also are individually assessed in conjunction with the A/I physician. The ASP/ID pharmacist and 3 other CPS involved in the creation of the BLAA and PAC have received formal hands-on training on penicillin allergy testing. The PAC process consists of a penicillin skin test, followed by the amoxicillin oral challenge.3The ASP/ID clinical pharmacist who is trained in penicillin skin testing performs all duties in PAC, with oversight from the A/I attending physician as needed. Currently, the ASP/ID pharmacist runs the PAC once a week with the A/I physician available if needed. Along with documenting an A/I clinic note detailing the events of PAC, the ASP/ID pharmacist also will add an addendum to the original BLAA note. If the allergy is removed through direct testing, it also can be removed from the patient’s profile after discussion with the A/I physician. Therefore, the full details necessary to evaluate, clarify, and clear the patient of their β-lactam allergy are in one place.