Penicillin Challenges - A 5 year review of penicillin de-labelling in a tertiary centre

ntroduction: Penicillin allergies are common with 1/5 patients reporting a reaction to penicillin. Whilst not inherently dangerous it does significantly limit antibiotic options for clinicians and there are consequences to using non-penicillin alternatives including increased cost as well as the increased risk of side-effects, and this can become clinically relevant in the setting of severe infections where alternative antimicrobials are less effective. As a result, hospitals with allergy services have focused on de-labelling penicillin allergies either through a direct oral challenge in low-risk patients, or skin testing and challenge in higher risk patients.
Method: A 5 year retrospective review of penicillin allergy referrals to our immunology service was conducted. Direct oral challenge was offered to low risk patients and skin testing with amoxicillin, benzylpenicillin and commercial Diater extracts with the major and minor determinates for those deemed higher risk. We recorded how many were given an oral penicillin challenge and how many subsequently tolerated penicillin. This review received ethics approval QA/86746/MonH-2022-315887(v1).
Results: 311 referrals were reviewed over a 5 year period, and half were sent for skin testing, whilst the other half were given a direct oral challenge. We were able to de-label over 80% of those referred. A higher proportion of those directly challenged went on to be de-labelled compared to those sent for skin testing. Over 5 years there appears to be a trend towards reducing skin-testing and more towards direct challenges. An interesting finding was that patients with skin positivity to amoxicillin were successfully challenged to a penicillin with an alternative side chain.
Conclusions: Penicillin allergy is common, and the label persists through the patient's healthcare journey. Penicillin de-labelling, when performed by a specialist centre, is safe and highly effective in removing incorrect labels. Trialing alternate penicillins is not standard practice but does open therapeutic options for patients.