BOSTON -- A large majority of patients at an allergy clinic who said they were allergic to penicillin had negative responses to the agent in skin testing, researchers reported here.
Of the 66 patients who underwent a penicillin skin test, 58 (88%) tested negative, while the most common reason for refusing a penicillin skin test was that the patient was on interfering medications, according to Allison Ramsey, MD, and S. Shahzad Mustafa, MD, both of Rochester Regional Health in Rochester, New York.
Action Points
- Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
While 10% of the U.S. population reports being allergic to penicillin, 90% are not allergic, and less than 0.1% of the 25 million patients who are allergic to penicillin undergo penicillin skin testing annually, Ramsey noted in a at the American College of Allergy, Asthma and Immunology meeting.
"Patients end up on more costly second-line antibiotics that carry more adverse effects. This has implications for antimicrobial resistance," she noted.
From April to June 2017, two allergy physicians at the Rochester health system, which sees about half pediatric and half adult patients, obtained a detailed penicillin allergy history of 987 patients. This was an average of about 12 half-day sessions per week.
A penicillin skin test (PST) was then offered to all patients with an appropriate history, as well as a timed PST plus amoxicillin challenge in negative patients. The average time for penicillin skin test and challenge was about 71 minutes.
About 60% of patients were women, with an average age of 32, and were about evenly split between first-time and follow-up visits. Penicillin or multiple drug allergy was the chief complaint in about a quarter of patients, followed by asthma (23%), allergic/rhinoconjunctivitis (21%), and food allergy (17%).
Overall, 155 patients (15.7%) reported a penicillin allergy. Nearly half said it had been more than 10 years since they last had a reaction to the drug. Ramsey said that was particularly important because "it's come up during discussion today that allergy may be one that tends to resolve over time."
A little over half of patients reported a general non-specific rash as an allergic reaction to penicillin, with about 30% reporting hives and about 6% who didn't know their reaction history. Six patients were de-labeled based on their history, and a direct challenge was performed in two patients. Around 43% of patients who reported an allergy to penicillin had a PST.
If a skin test was not performed, patients were asked to give a reason why. About a quarter of patients cited interfering medications with antihistaminic properties. There were 16% who said no based on time constraints, but 14% who were scheduled for skin test or a direct challenge at a future time, and only 7% who expressed anxiety about needle testing.
Ramsey said that the study provides a "real-world representation" of how feasible it is to do PST in an outpatient allergy office, regardless of a patient's chief complaint.
"We've seen a lot of great data coming out of inpatient antimicrobial stewardship programs, and this is a model of how penicillin skin testing can be improved with initiatives like this," she said. "These patients are coming through our doors every day."
Primary Source
American College of Allergy, Asthma and Immunology
Ramsey AC and Mustafa SS "A penicillin skin testing initiative in an outpatient allergy practice" ACAAI 2017; Abstract OR005.