Ninety percent of penicillin allergy cases misdiagnosed, research finds

Approximately 90 percent of patients in Hong Kong labeled as allergic to penicillin—a common antibiotic used during surgeries to treat bacterial infections—were misdiagnosed, researchers from the University of Hong Kong’s Faculty of Medicine found.

The findings, revealed on Wednesday, follows the research team's analysis of data from more than 4,700 knee replacement surgeries performed at Queen Mary Hospital between 1993 and 2021.

The misdiagnosis has led to many patients being prescribed alternative medications that are less effective and carry higher risks, researchers said.

Patients labeled as penicillin-allergic were found to have a three times higher risk of post-surgical infection.

During the study, the team also reassessed 11 individuals previously classified as penicillin-allergic and found that all had been incorrectly diagnosed.

Philip Li Hei, who led the research, attributed the misdiagnosis to doctors' reliance on clinical diagnoses without conducting drug sensitivity tests—a situation resulting from time constraints during treatment.

The team also noted that over 140,000 individuals in Hong Kong have been misdiagnosed as allergic to the antibiotic.

In response, the Faculty of Medicine has initiated a pilot scheme at the university’s community pharmacy designed to provide formal allergy assessments for residents.