# P-899. Assessing Documented Beta-lactam Allergies at a Large Comprehensive Cancer Hospital

## TL;DR

This study found that many cancer patients with documented beta-lactam allergies can safely tolerate these antibiotics, suggesting a need for better allergy evaluations to improve antibiotic use.

## Contribution

The study provides empirical evidence on beta-lactam allergy documentation and tolerance in cancer patients, supporting antimicrobial stewardship improvements.

## Key findings

- Over 70% of patients with documented beta-lactam allergies received a beta-lactam antibiotic without severe reactions.
- Aztreonam was used in 22% of patients, but most had low PEN-FAST scores indicating low allergy risk.
- PEN-FAST scores did not significantly correlate with the use of aztreonam or alternative antibiotics.

## Abstract

Beta-lactam allergies are documented in up to 10% of the population. True allergic reactions requiring the use of aztreonam, or other alternative antibiotics, account for less than 2% of patients. Avoidance of beta-lactam agents is associated with higher health care costs, increased risk of Clostridium difficile infections, and higher mortality rates. We aimed to characterize documented beta-lactam allergies in patients living with cancer.

This is a single-center retrospective study of hospitalized adult patients living with cancer having a documented beta-lactam allergy between 1/1/2024 through 12/31/2024. We assessed documented reactions, inpatient administration and outpatient prescriptions of antibiotics, and stratified patients for risk of having a true beta-lactam allergy using the PEN-FAST score.

Out of 49,825 hospital admissions, we identified 2658 (5%) patients reporting 2997 beta-lactam allergies. A solid tumor malignancy was the primary cancer diagnosis in 78% of patients. Penicillin (1870/2658, 70%) was the most common documented allergy, followed by a cephalosporin (23%). More than half of patients (57%) had a single reported reaction. Dermatological reactions listed as itching/rash or hives was reported by 49% and 30%, respectively. Anaphylaxis or a severe reaction was reported by 20% of patients. A PEN-FAST score of 0 and 2 was calculated for 779 (29%) and 1470 (55%) patients, respectively. Almost 70% (1831/2658) of patients received at least one dose of a beta-lactam, commonly with a cephalosporin (54%) or a carbapenem (28%), with no documented severe reactions. Aztreonam was administered to 588 (22%) patients in which 82% (484/588) had a PEN-FAST score of 0 or 2. There was no statistical significance in PEN-FAST scores and receiving either aztreonam or an alternative antibiotic.

Evaluation of our patients’ documented beta-lactam allergies revealed that a large portion of patients tolerated a beta-lactam antibiotic. A formal inpatient beta-lactam allergy evaluation service could aid in antimicrobial stewardship efforts to decrease aztreonam use and to remove inpatient beta-lactam allergy labels.

All Authors: No reported disclosures