This specialist Guidelines summary provides a framework for the set-up and delivery of penicillin allergy de-labelling services by non-allergists. It details appropriate patient selection, risk stratification, minimum safety standards, conduct of a drug provocation test, and the degree of oversight required from allergy or immunology specialists. The guideline is intended to supplement the 2015 British Society for Allergy & Clinical Immunology (BSACI) guideline Management of allergy to penicillin and other beta-lactams.
This summary is intended for use by non-allergists with an interest in clarifying the penicillin allergy status of their patients. The target population is adults and children with an untested label of penicillin allergy. For the complete set of recommendations, please refer to the full guideline.
Risk Stratification
- A detailed drug allergy history, including review of prescription records where possible, will allow the clinician to stratify the risk of allergy. Patients may report symptoms and/or signs:
- in keeping with non-immunological side effects from penicillin antibiotics and probable non-allergic phenomena (see Table 1). This group is often referred to as ‘low risk;’ however, there is wide variation within this definition and the Guideline Writing Group preferred to consider patients as either ‘suitable’ or ‘not suitable’ for direct drug provocation testing (DPT)
- consistent with either type 1 (IgE-mediated) immediate hypersensitivity reactions or type 4 (typically T cell-mediated) delayed reactions (see Table 2). These patients are considered not suitable for direct DPT by non-allergists and require evaluation by an allergy specialist
- entirely in keeping with side effects and other non-allergic phenomena, in whom no allergy testing is indicated (see Table 1). However, such patients may require reassurance from a test as proof of tolerance and, in this situation, a DPT could be considered.
- There are patients in groups 1 and 2 (see above) in whom there is a clinical imperative for treatment with penicillin but a DPT is not appropriate—for example, treatment of syphilis in pregnancy. These patients must be evaluated and treated by an allergy specialist who may perform desensitisation
- All patients labelled as ‘penicillin allergic’ attending secondary or tertiary care should be considered for penicillin allergy testing
- Non-allergists providing de-labelling services should be networked with a specialist allergy immunology service for advice and support.
Table 1: Low-risk Symptoms in Adults and Children
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[B] Benign defined as non-urticarial, non-itchy, non-blistering, short-lived (less than 24 hours), and did not require treatment.
[C] ‘No other history available’ assumes that such information has been sought from patients, carers, relatives, and healthcare records where possible.
Table 2: Exclusion Criteria for DPT in Adults and Children
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Conduct of DPT
- Where a patient reports a reaction to penicillin in which only symptoms from Table 1 occurred, and none of the exclusion criteria from Table 2, a direct DPT can be performed
- See Table 3 for the safe conduct of DPT. A single or graded DPT may be used, depending on local preference of the allergy team supporting the set-up of the de-labelling service
- Amoxicillin is the drug of choice unless the index penicillin is known to be different, in which the index penicillin should be used. Amoxicillin is widely used in routine NHS practice for direct oral penicillin challenge (DPC) and has a more favourable side effect profile compared with other penicillins such as co-amoxiclav
- All personnel administering a DPT should have up-to-date training in advanced life support and management of anaphylaxis, and immediate access to on-site resuscitation facilities, including provision of critical care
- All patients identified as low risk for true penicillin allergy should be offered direct DPT, providing no exclusion criteria are met
- Non-allergists should perform DPT in low-risk patients in a setting where allergic reactions, including anaphylaxis, can be treated.
Table 3: Principles for the Conduct of a Drug Provocation Test
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DPC=direct oral penicillin challenge; DPT=drug provocation testing.
Use of Prolonged DPT
- Consultation with the local/regional allergy service providing oversight for the de-labelling service should be sought to define which patients require a prolonged DPT and how long this should be
- A prolonged (multiple doses) DPT should be considered when the index reaction occurred after the second or subsequent dose of a course of penicillin (or where the timing of the reaction is unknown)
- Where indicated, a prolonged DPT lasting 3 days is sufficient in the majority of patients. If the index reaction is clearly remembered to have occurred after more than 3 days, advice should be sought from the local or regional allergy service as to how long to extend the DPT.
Paediatrics
- True allergic reactions to penicillin are less common than in adults
- Reactions, if they develop, are usually mild–moderate and occur 3–4 days from the start of the challenge. Recommendations for children of all ages are the same as those for adults, in terms of risk stratification and the conduct of DPT (see Tables 1–3)
- Doses of medication should be age adjusted.
References
References