Patients labelled as allergic to penicillin – usually incorrectly – are three times more likely to develop a serious joint infection after knee surgery as they receive weaker antibiotics, a Hong Kong study has found, with researchers urging them to seek an evaluation especially before their operation.

A team from the University of Hong Kong, which released the findings of the study on Wednesday, said that about 90 per cent of patients recorded as being allergic to the commonly used antibiotic were wrongly labelled.

“We found that if patients are wrongly labelled as allergic to penicillin, there can be a very serious consequence, which is infection,” said study co-leader Dr Steve Cheung Man-hong, an honorary clinical assistant professor in the department of orthopaedics and traumatology at HKU.

“There should be appropriate and timely evaluation on allergy labels.”

The study analysed 4,730 patients who had undergone knee replacement surgery at Queen Mary Hospital in Pok Fu Lam between 1993 and 2001.

Among them, 165 were labelled allergic to penicillin, the most common and first-line antibiotic used by doctors before joint surgery to prevent infections.