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© DR P.MARAZZI/SPL. Allergic reaction to penicillin.
Simple decision aid to identify patients at low risk of penicillin allergy

By Nicole MacKee
A simple, point-­of­-care decision aid can help to identify patients with low­-risk penicillin allergy without formal allergy testing, say researchers in JAMA Internal Medicine.

An Australian­-developed penicillin allergy clinical decision rule was shown to have a negative predictive value of 96.3%, the researchers reported.

Patients were classi­fied as low risk of penicillin allergy if they scored less than three points on the PEN­-FAST decision rule. This rule com­prised: PENicillin allergy, Five or fewer years a go (2 points); Anaphylaxis/angioedema or Severe cutaneous adverse reaction (2 points); and Treatment required for allergy episode (1 point).

The PEN­-FAST rule was validated in a prospective cohort of 622 patients in Melbourne, and externally validated in three retro­spective cohorts (total 945 patients) in Sydney and Perth, Australia, and Nashville, USA. Of the 460 patients classified as low-risk in the Melbourne cohort, only 17 (3.7%) had positive results on allergy testing. Similar findings were seen on external validation.

Lead author Associate Professor Jason Trubiano, Infectious Diseases Physician and National Health and Medical Research Council Early Career Researcher at the University of Melbourne, said the PEN-FAST rule was one of the first clinical decision rules to be validated in one country, and externally validated in another.

‘It’s a very safe tool for clinicians to use. The first port of call for wider use would be in hospital settings, which is where most broad-spectrum antibiotics are prescribed,’ he told Medicine Today.

‘The next frontier will be rolling out these tools in general practice, but more research is needed to show that we can challenge low-risk people in the general practice setting as well as in the hospital setting.’

Associate Professor Trubiano said earlier studies had shown that at least 18% of people presenting to hospitals reported an antibiotic allergy, with about 10% reporting a penicillin allergy (J Antimicrob Chemother 2016;71: 1715-1722).

‘And the prevalence is much higher in those who need antibiotics the most – for example, those who are immunocompromised or have chronic lung infections,’ he said.

‘We also know that among general medical patients, almost 50% of people who report a penicillin allergy are low risk, but a decision rule was needed to improve the risk stratification of these patients.’

Associate Professor Trubiano said delabelling penicillin allergy was important in efforts to tackle antimicrobial resistance and improve patient outcomes. He pointed to 2018 UK research showing that penicillin allergy was associated with an increased risk of methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile infections (BMJ 2018; 361: k2400).

‘When a patient has a penicillin allergy, you are much more likely to use inferior and broad-spectrum antibiotics and they are the antibiotics that then drive antimicrobial resistance in Australia and globally.’
JAMA Intern Med 2016; doi:10.1001/jamainternmed.2020.0403.