Background: Penicillins (PCN) are commonly used to treat cystic fibrosis (CF) exacerbations, such as amoxicillin when combined with clavulanate. Allergies to PCN are the most commonly reported medication allergy, reported in 5-20% of children and up to 33% of people with CF (PwCF). PCN allergy may result in alternate antibiotic usage including non-PCN antibiotics such as clindamycin, that also treat MRSA, or cephalosporins, if tolerated. Previous work at our institution showed that 76% of PCN Allergies in pediatrics were low-risk and 100% of those were negative for allergy upon oral challenge. [1]
We applied this protocol in PwCF to assess for PCN allergy risk level and demonstrate that those who are categorized into a low-risk group by an allergy questionnaire will tolerate a modified 3-tier penicillin allergy testing process and, secondarily, will result in an increase in PCN usage.
Methods: PwCF greater than 3 years old with a recorded PCN allergy were included. Our survey was administered to identify the level of allergy risk. Those who were low-risk on survey then underwent modified 3 tier allergy testing (1. skin prick, 2. intra-dermal skin testing, 3. oral challenge) and assessment for reactions immediately following and 24 hours later. Those with no reaction were considered not PCN allergic. This information was conveyed to the primary physician, CF team, and the allergy was removed from the electronic medical record. Chart review was used to evaluate antibiotic usage (type and frequency) and respiratory bacterial growth before and after study participation in all subjects. Assessments were administered quarterly for 12 months after testing. The study was IRB approved.
Results: Twelve PwCF with PCN allergy at our center participated in the study. Of those, 50% (6) were low-risk on questionnaire, of whom 5 completed 3-tier allergy testing. All 5 tested (100%) did not react either immediately or at 24 hours. Therefore, all were de-labeled and no longer consider allergic. As for clinical effects, in the low-risk cohort 6% (1/16) of antibiotic courses were PCN before testing which increased to 69% (9/13) after de-labelling. Conversely, very few antibiotics were PCN in the cohort illegible for testing, 10% (2/20) before and 12% (2/17) after the survey (see figure below). No episodes of anaphylaxis occurred. On survey, 80% of families (4/5) were comfortable or very comfortable with PCN usage after de-labelling. One child developed a rash while on a PCN, although unclear if directly related. There was no difference found in the type of bacteria grown before and after the study period in either population.
Conclusions: Antibiotics, including PCN, are common therapy in PwCF. Of the PCN allergic PwCF in our population, 50% of them were low-risk, all of whom were negative for PCN Allergy on 3-tier testing. There was an increase in PCN based antibiotic usage afterwards, without any anaphylactic events. The utilization of this questionnaire in PwCF may facilitate de-labeling of PCN allergies and increased use of preferred antibiotics.
Acknowledgements: Supported by the Medical College of Wisconsin Department of Pediatrics and the Division of Emergency Medicine.
References: [1] Vyles, et al. Allergy Testing in Children With Low-Risk PCN Allergy Symptoms. Peds. 2017 Aug;140(2)
