Simple Decision Rule Helps Identify People at Low-Risk for Penicillin Allergy

By Megan Brooks

March 18, 2020

NEW YORK (Reuters Health) - A simple clinical decision rule for penicillin allergy can help doctors and antimicrobial-stewardship programs identify people at low-risk of penicillin allergy at the point of care, report doctors from Australia who developed and validated the PEN-FAST rule.

"It's important to determine tools that allow clinicians to accurately and quickly assess presumed penicillin-allergic patients to determine who is likely to not have a true penicillin allergy," said Dr. Jason Trubiano of the University of Melbourne, in Heidelberg.

"This is a group of patients we should be targeting for penicillin allergy 'de-labelling' (removing their allergy with testing) so we can use our front-line antibiotics more appropriately, such as penicillins," he told Reuters Health by email.

Dr. Trubiano and colleagues developed the PEN-FAST rule from an internal derivation and validation cohort of 622 patients (59% women; median age, 60 years) from two sites in Melbourne, and an external validation cohort of 945 patients (70% women; median age, 55 years) from Sydney and Perth, in Australia, and Nashville, Tennessee.

Patients reporting a penicillin allergy underwent penicillin-allergy testing using skin prick, intradermal, or patch testing and/or oral challenge (direct or after skin testing).

On multivariable analysis, four features were associated with a positive test result, summarized in the mnemonic PEN-FAST: penicillin allergy, five or fewer years ago, anaphylaxis/angioedema, severe cutaneous adverse reaction (SCAR) and treatment required for allergy episode.

The top criteria were an allergy event occurring five or fewer years ago, garnering two points, and anaphylaxis/angioedema or SCAR (two points). The minor criterion - treatment required for an allergy episode - was given one point.

"Internal validation showed minimal mean optimism of 0.003 with internally validated area under the curve of 0.805," the study team reports in JAMA Internal Medicine.

A PEN-FAST score of less than three points suggests a low risk of penicillin allergy, they report. At this cutoff, only 17 of 460 patients (3.7%) had positive results on penicillin-allergy testing, with a negative predictive value of 96.3%. External validation produced similar findings.

"PEN-FAST may aid the risk stratification of patients with penicillin allergy to facilitate implementation of delabeling strategies and safe beta-lactam prescribing," the authors say in their paper.

"This tool is ready for clinical practice," Dr. Trubiano told Reuters Health. "It has been developed in Australia and then validated in other centers in Australia and U.S. It can be used by clinicians and pharmacists at the front line to assess a penicillin allergy and aid in selecting the right penicillin antibiotic."

The study had no commercial funding and the authors have declared no conflicts of interest.

SOURCE: JAMA Internal Medicine, online March 16, 2020.