Bedside allergy test increases number of patients receiving penicillin

Patients who have previously reported a penicillin allergy are often able to receive the drug after a simple bedside skin test, a new study led by Sunnybrook has found.

“The majority of patients who report an allergy to penicillin could likely tolerate it if they received it. Doing a bedside allergy skin test helped us determine who those patients were,” says Dr. Jerome Leis, lead study author and Medical Director of Infection Prevention and Control at Sunnybrook Health Sciences Centre. “Many people outgrow their penicillin allergy, or may be able to receive the drug in controlled doses.”

Pharmacists were trained to perform beta-lactam allergy skin testing (BLAST) at the bedside of hospitalized patients, which included a prick test with a small amount of the penicillin on a patient’s skin. Antibiotics from the beta-lactam family, such as penicillin, are the preferred (and sometimes, only) treatment for many serious bacterial infections.

Thirty minutes after the skin test, if the patient showed no signs of an allergic reaction, such as swelling or a rash, they were then given a test dose of the drug. If no further reactions were observed after four hours, the patient then received the preferred penicillin-based treatment for their infection.

The multicentre study, which included three hospitals in Toronto, was a collaborative effort between antimicrobial stewardship, allergy, infectious diseases and pharmacy experts. Of the 85 patients identified to receive BLAST, 83 (99%) were switched to beta-lactams such as penicillin and finished their course of treatment without complication.

The results of the study show that bringing skin testing to the bedside improves treatment of serious infections. “In the past, we haven’t had the evidence to support skin testing, but this study has shown us what a positive difference bedside skin testing can make,” says Dr. Leis.

The study findings are particularly important for patients with life-threatening infections that are best treated with penicillin. One in ten Canadians report having a penicillin allergy, meaning those patients may receive less effective antibiotics to treat their infections and experience poorer outcomes as a result.

“In addition to some of the more toxic side effects associated with alternate therapy to penicillin, some of these alternative drugs don’t reach the site of infection. Limiting the use of those alternate therapies also reduces antibiotic resistance,” says Lesley Palmay, study co-author and Infectious Diseases Consult Service Pharmacist at Sunnybrook.

As a result of the study, which was published in the Clinical Infectious Diseases journal, Dr. Leis says bedside skin testing is standard practice at Sunnybrook. “Now, the right patient can receive the right antibiotic for their infection, without fear of an allergic reaction.”

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Sybil Millar, Communications Advisor
sybil.millar@sunnybrook.ca or 416-480-4040