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PEN-FAST 2.0 – Directly Testing for PCN Allergy – The PALACE RCT

August 7, 2023

Written by Jacob Altholz

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Starting with the PEN-FAST Decision Tool, direct oral challenges to low-risk individuals with reported penicillin allergies is safe, effective, and can remove a majority of mislabeled instances.

Making the PEN-FAST mightier
Standard of care currently uses a skin test before initiating an oral challenge to a penicillin allergy. This article analyzed the safety and efficacy of directly jumping to oral testing in individuals who are deemed low risk (PEN-FAST scoring lower than 3). Removal of an allergy test would make this feasible in the ED.

Patients (n=382) visiting 6 multinational outpatient allergy offices were randomized to either undergo skin testing and subsequent oral testing or oral testing alone (usually amoxicillin). All patients had to be low-risk by the PEN-FAST tool to be eligible. In both groups, only one individual experienced symptoms consistent with an immune-mediated reaction during the oral challenge itself (limited to 60 minutes). Adverse reactions and delayed allergic reactions identified at a 5-day follow-up were similar in rate between the groups, with no serious reactions reported at all.

It’s worth noting that the exclusion criteria were fairly restrictive, keeping out those with symptoms such as “nausea” or “headache” that are not consistent with truly allergic responses as well as anyone with a reported anaphylactic reaction to any medication whatsoever.

How will this change my practice?
Considering many of the patients I encounter say something along the lines of “their throat swells up” or “it just makes me feel bad,” I’m not sure I would run into many scenarios where testing is feasible before discharge. Still, in the right set of circumstances this could be a viable way to prevent the harm these mislabeled patients experience. Avoiding beta-lactams due to reported allergy can increase adverse events, medical mistakes, and drug-resistant organisms. Finding a way to remove this reported allergy is important since <5% of individuals reporting a penicillin allergy actually exhibit symptoms on testing.

Peer reviewed by Ketan Patel

Efficacy of a Clinical Decision Rule to Enable Direct Oral Challenge in Patients With Low-Risk Penicillin Allergy: The PALACE Randomized Clinical Trial. JAMA Intern Med. Published online July 17, 2023. doi:10.1001/jamainternmed.2023.2986

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