Creating and utilising the Wales Asthma Observatory to support health policy, health service planning and clinical research

Asthma is a public health challenge in Wales. In order and improve its outcomes and reduce its burden, reliable evidence on disease epidemiology is needed. In this thesis, I describe the development of a platform for asthma surveillance and research in Wales using routinely collected electronic health record (EHR) data in the Secure Anonymised Information Linkage (SAIL) Databank.To inform the development of operational definitions for asthma and its outcomes, I examine the contemporary approaches to defining asthma and assessing its out-comes using EHR data, and describe significant variations and suboptimal report-ing on these approaches. I highlight the need for valid, standardised methods to study asthma, and emphasise the increasing demand for improved reporting to support research transparency and reproducibility.Acknowledging the infeasibility of reference standards to define asthma in SAIL, I describe the development of latent class model to identify asthma patients in this databank. I assess the performance of this model in relation to other objective and self-reported measures of asthma.I also describe other methodological aspects of the development of the Wales Asthma Observatory, including asthma data profiling and identification of impor-tant data gaps.To demonstrate the Observatory’s utility for health policy and service planning, I highlight the variations in asthma epidemiology in Wales across age groups, gen-der, and socioeconomic deprivation levels. I found that asthma patients living in the most deprived areas had higher healthcare utilisation for asthma, indicating worse disease control, than those in the least deprived areas.Finally, I reflect on the experience of developing the Wales Asthma Observatory, recognising its strengths and limitations, and identify opportunities and challenges of maximising the use of routine data towards a learning health system for asthma in Wales