Clinical trial helps those with penicillin allergy

A team of researchers from Canada, the U.S., and Australia has found a “new approach to identifying patients at low risk of penicillin allergy, and determining the best way to test and treat them” in what’s been dubbed the PALACE study.

A penicillin allergy is regarded as a world health concern. According to researchers, one in every 10 patients has the allergy.

They say due to this, those patients are more likely to be prescribed alternative antibiotics that are often less effective against certain infections, which can lead to treatment failure, increased risks of antibiotic resistance, and the development of superbugs.

Fewer than five per cent of patients labelled as having a penicillin allergy are truly allergic, the study adds.

“The biggest takeaway from the PALACE study is that patients with a low-risk penicillin allergy, like a childhood rash, can safely have a test dose of penicillin to determine if they are still allergic,” said first author Dr. Ana-Maria Copaescu, an associate investigator in the Infectious Diseases and Immunity in Global Health Program at the Research Institute of the McGill University Health Centre (RI-MUHC).

“This will change the way doctors test for penicillin allergy in the future. Millions of patients worldwide, including millions of Canadians, will be able to have their penicillin allergy disproved by a safe single oral test dose following a carefully risk-validated risk assessment,” Copaescu, who was the leading investigator for the North American sites, continued.

“The PALACE study is the first international randomized study to look at reducing the burden of penicillin allergy by seeing if a simple test dose procedure following careful assessment can be used to disprove a patient penicillin allergy, rather than traditional skin or scratch testing,” added senior author of the study Pr. Jason Trubiano, who is the director of Infectious Diseases and head of Centre for Antibiotic Allergy and Research at Austin Health in Australia.

“With this new procedure, we can give back a lifesaving antibiotic, penicillin, to more than 90 per cent of patients that undergo testing.”

During the study, 382 adults were assessed using a specialized risk assessment tool called PEN-FAST.

They were then randomly assigned a direct oral penicillin challenge — test — or the standard approach, which involves penicillin skin testing followed by an oral challenge.

Researchers say this was to determine if the direct oral penicillin challenge was as effective as the standard method for removing the allergy label.

From there, the study found only one patient — 0.5 per cent — in each group experienced a positive reaction to the penicillin challenge, which indicated the direct oral penicillin challenge is just as effective as the standard method.

Researchers have also indicated that 80 per cent of people who have had a penicillin allergy for over 10 years eventually lose their sensitivity to the medication. However, they note many adult patients carry a penicillin allergy label from childhood.

“A penicillin allergy label can appear from multiple sources, such as avoidance as a result of family history or non-allergic mild side effects such as headache or stomach pain, skin rashes associated with viral infections in kids that are subsequently labelled as allergic, fear of the drug, etc.,” said Copaescu.

“For various reasons, unverified penicillin allergy labels are not often challenged. As a result, many patients receive broad-spectrum alternative antibiotics associated with increased healthcare cost and increased antibiotic resistance, and in some cases, higher rates of treatment failure, medication errors and undesirable side effects or complications.”

Results from the clinical trail have been published in JAMA Internal Medicine.