Single-step direct drug provocation testing is safe for de-labelling selected "non-low-risk" penicillin allergy labels.

Abstract Background Penicillin allergy labels are prevalent, and removal of incorrect labels improves patient outcomes and health economics. Labels may be classified as "low-risk", or "non-lowrisk", the latter chiefly where symptoms suggest IgE-mediated etiology. Traditionally, "non-low-risk" allergy labels are assessed by penicillin skin testing followed by graded multi-step penicillin drug provocation testing (DPT). Objective To assess the safety of assessing "non-low-risk" labels with single-step direct DPT. Methods We consecutively enrolled inpatients and outpatients of a teaching hospital in Sydney, Australia with pencillin allergy labels requiring penicillin for first-line treatment. Patients were classified as "low-risk" or "non-low-risk" based on allergy labels. All patients proceeded directly to amoxicillin DPT unless there was a history of anaphylaxis within 10 years of assessment to a beta-lactam (excepting cefazolin), or Gell and Coombs Type 2, Type 3 or severe Type 4 reaction. This was followed by a course of amoxicillin. Results One-hundred-and-forty-nine patients (41 inpatients, 108 outpatients) were enrolled. Zero patients were excluded from the study. Zero patients experienced life-threatening reactions to the protocol. Eighty-five patients reported "non-low-risk" allergy labels. One patient developed generalised pruritus and rash which resolved with standarddose antihistamines. Two developed delayed benign maculopapular exanthem. Three experienced diarrhoea during the course of amoxicillin. Conclusion In our cohort, direct single-step DPT was safe with only 6 patients with “non-low risk” allergy experiencing benign reactions. We hope further study can be performed into single-step direct DPT for interrogating “non-low risk” penicillin allergy labels