Background
Population-based studies have demonstrated the potential of use of ‘big
data’ in clinical and drug allergy research.1-4 The
availability of longitudinal datasets can explore new dimensions of drug
allergy research which would not have been possible with only
traditional single-centre or cross-sectional studies. For example, we
previously reported one of the largest drug allergy epidemiological
studies by taking advantage of Hong Kong’s unified electronic healthcare
record system with data from more than 95% (7.1 million) of the
population.1 Based on population-wide data, we were
able to accurately report the near-absolute prevalence and annual
incidence of reported drug and beta-lactam allergies. However, at the
time, we were only able to provide a condensed one-year snapshot on the
landscape of drug/beta-lactam allergy and did not further analyse the
granularity of individual patient data; such as specific-drug allergy
culprits, individual patients’ age of reported drug allergy or duration
of reported drug allergy. More detailed analyses are also important to
identify country- or population-specific characteristics, which may
vastly differ from Western cohorts, to further inform future drug
allergy interventions and research.5,6
Another important limitation to drug allergy evaluation and research is
the ability to accurately identify specific culprit allergens. For
example, it is well established that up to 90% of all reported
penicillin ‘allergy’ are incorrect after allergy evaluation, likely due
to initial misdiagnoses or loss of sensitisation over
time.7-10Alternatively, mislabelled drug allergy can also be due to the
possibility of missing hidden allergens found within drugs or vaccines
such as in the case of excipient allergies.11,12Although an uncommon cause of drug allergy, excipient allergy can almost
never be excluded in countries lacking in pharmaceutical legislations to
mandate complete ingredient disclosure in registered medications. This
can and has led to cases of missed- and mis-diagnoses with potentially
lethal consequences.13-15 The devastating impact of
such failures in pharmaceutical legislations have been exemplified
during global COVID-19 vaccination campaigns. Despite genuine vaccine or
excipient allergy being exceedingly rare, the indirect consequences from
the fear of potential excipient allergy and inability to identify
potential excipients among culprit drug formulations greatly impeded
vaccine uptake and fuelled vaccine hesistancy.16-18
To overcome these issues, the Comprehensive Excipient and Drug Allergy
Registry (CEDAR) was established in Hong Kong – allowing the use of big
data to investigate reported drug allergies in detail, and to help
establish an excipient registry to facilitate comprehensive drug allergy
evaluations. Utilising CEDAR, we investigated the 5-year trend of
detailed drug allergy epidemiology and the potential role of an
excipient registry to aid drug allergy evaluation. In particular, we
selected polyethylene glycol (PEG), one of the most widely implicated
excipients since the launch of mRNA COVID-19 vaccines, as an example for
the potential use of excipient registries.