Impact of penicillin allergy records on antibiotic costs and length of hospital stay: a single-centre observational retrospective cohort

Introduction: Patients with a penicillin allergy record are usually prescribed non-penicillin antibiotics and have worse health outcomes. This study explored the impact of penicillin allergy records on antibiotic treatment costs and patient length of stay. Methods: Patients prescribed a systemic antibacterial agent between April 2016 and March 2018 in a 750-bed English hospital were included in this study. The following data were extracted for each patient: age, sex, comorbidities, infection treated, antibiotic usage (defined daily dose), hospital length of stay and penicillin allergy status. Multi-variable log-linear modelling was used to determine associations between patients labelled as penicillin allergic and total antibiotic costs and length of stay. Using the above models, the potential reductions in total cost and hospital bed-days of ‘delabelling’ patients with a penicillin allergy record were estimated. Results: Penicillin allergy records were present in 14.3% of hospital admissions and were associated with an increase in non-penicillin antibiotic prescribing, a 28.4% increase in antibiotic costs and 5.5% longer length of hospital stay compared with patients without a penicillin allergy record. Patients with a penicillin allergy record accounted for an excess antibiotic spend of £10,637 (2.61% of annual antibiotic drug spend) and 3522 excess bed-days (3.87% of annual bed-days). Delabelling 50% of patients with a self-reported penicillin allergy record would save an estimated £5501 in antibiotic costs and £503,932 through reduced excess bed-days. Conclusion: Delabelling patients with a self-reported allergy record has potential to reduce antibiotic costs, but its biggest cost impact is via a reduction in excess bed-days.