The effect of reported penicillin allergy on length of stay for patients admitted to internal medicine services: A retrospective cohort study

Introduction: Penicillin allergy is the most common medication allergy reported in the United States; however, >90% of these patients can tolerate penicillins. Reported penicillin allergy is associated with increased morbidity and mortality for patients. This retrospective, observational study evaluates the effect of reported penicillin allergy on length of stay (LOS) for adult patients admitted to the internal medicine services of a tertiary care, academic medical center. Materials and Methods: We evaluated adult patients admitted to internal medicine services from June 2014 to June 2019 comparing those who reported penicillin allergy to those who did not. Patients who did not receive antibiotics were excluded. Univariate analyses were performed on multiple demographic and clinical variables between patients who do and do not report a penicillin allergy. Multivariable linear regression was used to model the effect of reported penicillin allergy on LOS. Results: 14,144 patients were admitted to internal medicines services during the study period, with 8697 patients receiving an antibiotic during their admission. 10.5% of these patients reported a penicillin allergy. The unadjusted mean LOS for patients who report penicillin allergy was 10.4 days, while the unadjusted mean LOS for patients who do not report penicillin allergy was 9.3 days. Adjusting for covariates, the estimated LOS for patients who report penicillin allergy was 11.1 days, while the estimated LOS for patients who do not report penicillin allergy was 9.5. Conclusions: A reported penicillin allergy is associated with an increase in estimated LOS of 1.6 days. The following core competencies are addressed in this article: Systems-based practice, Medical knowledge.