Direct oral challenge for rapid penicillin de-labelling in acute admitted general medical patients.

Abstract

Background: Allergy to penicillin is commonly reported in the community. However, the majority of patients are not allergic when formally tested. In low risk patients, rapid allergy testing has been performed with skin prick/intradermal or direct oral challenge in an outpatient and Emergency Department setting. However, a direct oral challenge in acute hospital inpatient has not been reported. Aim(s): To access the feasibility and safety of rapid penicillin allergy delabelling with direct oral challenge in admitted acute general medical patients. Method(s): Patients admitted to a general medicine unit were screened for a history of penicillin allergy by unit pharmacists. A detailed history was obtained on patients with a self-reported penicillin allergy to assess suitability for a direct oral challenge: including current clinical status, and pretest probability based on the Australian Society of Allergy and Clinical Immunology (ASCIA) Guidelines. Suitable patients where challenged with a single 250mg Amoxicillin oral dose, followed by a 3 days course of 250mg Amoxicillin TDS. Result(s): 1808 patients were admitted to a general medicine unit from February to June 2018. 181 (10%) patients had a documented penicillin allergy. Rash (45%) is most commonly reported followed by unknown/non-specific reaction (21%) and gastro-intestinal symptoms (10%). Only 28 (16%) of patients met criteria for high pre-test probability of reaction. 35 (19%) patients were recruited to a challenge. 34 patients tolerated the challenge without any reactions. Only 1 patient reported a rash. 13 patients had been de-labelled from June 2017 to February 2018 using the same protocol, resulting in total of 47 patients successfully de-labelled since June 2017. Data collection is ongoing. Conclusion(s): Penicillin allergy de-labelling with a direct oral challenge in an acute hospital inpatient setting is likely safe and feasible. This approach may improve patient outcome with better anti-microbial usage and reduce burden on outpatient immunology waiting lists.