(1235) Pharmacist-led Outpatient Penicillin Allergy Skin Testing

Objectives: The objective of this study was to assess the feasibility and implementation of pharmacist-led outpatient penicillin allergy testing clinic. Penicillin allergy skin testing (PST) is recommended to facilitate optimizing antibiotics and is recommended by the American Academy of Allergy, Asthma, and Immunology (AAAAI), Infectious Disease Society of America (IDSA), and the American College of Obstetricians and Gynecologists (ACOG). When assessing penicillin allergy status, PST and by mouth (PO) amoxicillin challenge have a 99% negative predictive value. There is a projected shortage of physicians, including allergists and immunologists by 2034. Pharmacists are in a prime position to collaborate and provide penicillin allergy testing given their knowledge on drug-allergy management, involvement with antimicrobial stewardship, and availability within health-systems. Prior studies have focused on pharmacists performing inpatient PST.

Methods: This single-site, retrospective cohort evaluated the implementation of outpatient PST conducted by pharmacists from July 2022 through July 2023. The study site consisted of an outpatient clinic within a non-academic community hospital. PST consisted of two parts, the scratch test followed by five intradermal injections. If both PST parts showed no penicillin allergy, patients proceeded to the final step for the PO amoxicillin challenge. Patients were observed for 15 minutes after each PST step and for at least 61 minutes following the amoxicillin challenge. Outpatients were included if they were at least 18 years of age, had a history of a penicillin allergy with reactions including anaphylaxis greater than 10 years ago, urticaria, swelling, and unknown, and a physician’s referral for an outpatient PST. Patients were excluded if they had a prior PST or reaction of anaphylaxis to penicillin within the prior 10 years. The primary outcome was the percentage of patients who successfully passed the three components of the penicillin allergy test and subsequently de-labeled penicillin allergy. Secondary outcomes included percentage of patients who received appropriate antibiotics following allergy de-labeling, incidence and type of IgE mediated penicillin allergic reactions, average reimbursement per patient, and average time to complete testing. Facility billing was conducted using ICD-10 codes, Z88.0: allergy status to penicillin and T36.0X5D: adverse effect of penicillins, subsequent encounter, and two CPT codes, 95018: percutaneous and injection allergy test drug/biologics and 95076: ingestion challenge initial 120 minutes. Pharmacists were also responsible for all clerical tasks including scheduling patients, making reminder phone calls and billing following the completion of the visit.

Results: A total of 197 outpatients received penicillin allergy testing during the study period. Physician specialties who referred patients were orthopedics, obstetrician-gynecologists, infectious disease, urology, urogynecology, cardiothoracic surgeons, and primary care providers. For the primary outcome, 185 patients (93.91%) were successfully de-labeled. All de-labeled patients received appropriate antibiotics following testing. There were 11 patients who developed minor itching with or without a localized rash following the amoxicillin, and one patient had a delayed reaction of rash 12 hours after the amoxicillin that resolved with an antihistamine. One patient had their penicillin allergy re-labeled which was identified and corrected by the pharmacist. The average reimbursement was $473 per patient with an average time to complete an appointment being 100 minutes.

Conclusions: This study supports the pharmacist as the provider in de-labeling penicillin allergies and improving patient health outcomes. Furthermore, given the availability of having a dedicated pharmacist, providers could refer multiple patients and expect a reasonable turnaround time to complete testing, including same day testing. Pharmacists, in collaboration with multiple physician specialties, successfully implemented an outpatient penicillin allergy testing service to safely de-label patients and support antimicrobial stewardship. The implementation of the clinic resulted in the approval of a full-time infectious disease pharmacist to run and expand the penicillin allergy testing service for the organization.