Collection of anonymised patient data
Anonymised patient data from the Hospital Authority was collected by the
Information Technology and Health Informatics Division, Hospital
Authority Head Office. Informed consent was waived (because all data
were anonymous and collected retrospectively) and data extraction was
approved by the institutional review board of the University of Hong
Kong and Hospital Authority Hong Kong West Cluster. Hong Kong is a
unique entity where the Hospital Authority is the sole publicly funded
healthcare system for the entire territory. It possesses facilities in
seven regions (Hong Kong East, Hong Kong West, Kowloon Central, Kowloon
East, Kowloon West, New Territories East, and New Territories West),
comprising 43 hospitals, 49 specialist outpatient clinics, and 73
general outpatient clinics; it provides approximately 90% of all
in-patient services.19 All clinical services utilise a
unified ‘Electronic Patient Records’ system, providing medical records
for over 7.3 million individuals. This system allows complete and
uniform drug allergy data to be gathered and analysed. A snapshot of
cross-sectional data from all available patient records was retrieved as
of 23rd July, 2021. Physician-reported drug allergy,
age at the time of reported drug allergy and names of reported culprits
were collected. Incidence of newly reported drug allergy, as well as all
cases of anaphylaxis and Stevens-Johnson syndrome from
1st January, 2016 to 31st December,
2020 were reviewed. Drugs were categorised according to the British
National Formulary Drug Classes, except for non-steroidal
anti-inflammatory drugs (NSAIDs), which were separated into its own
category.20 Drugs which were entered as ‘free text’
into the electronic system were checked and converted back to structured
drug items when possible. Those ‘free text’ reported drug allergy which
could not converted or were incomplete were excluded from analysis.
Drugs which did not fit into any drug classes were categorised as
‘Others’ and listed in Supplementary Text 1.