Interstitial Lung Diseases (ILD) are a large group of conditions characterised by scarring of the lungs. In some cases, the cause for the lung scarring is clear. For example, problems with the immune system such as rheumatoid arthritis or working with asbestos. However, in many cases, the cause is unknown (Idiopathic pulmonary fibrosis, IPF). The burden of all-encompassing ILD and its various types is not well established in the UK.
For this research, we propose to use information from primary care (Clinical Practice Research Datalink) and secondary care databases (Hospital Episode Statistics and Office of National Statistics) to investigate how many people in the UK have interstitial lung disease, and what type of ILD diseases they have. We will also explore the number of people diagnosed with specific types of ILD over the past 10 years, ascertain any trends during this time and whether these disease patterns differ by different types of ILD and how many have died as a result of their ILD.
We hope that through this study we will develop a better understanding of burden of the various conditions that come under the heading of interstitial lung disease and in so doing support the further research that is needed in this area.
ILD is an umbrella term which encompasses several conditions with different clinical pathways leading to varied health outcomes. Pharmacological intervention varies depending on the underlying diagnosis, disease severity and trajectory and patient choice. In this study, we will identify an ILD cohort which represents the range of different conditions and use it to estimate the prevalence and incidence of all ILD. Given the heterogenous nature of the conditions and potential inaccuracies in diagnostic coding it is considered likely that reliance on simple lists of clinical diagnostic codes may lead to potential under- and over- ascertainment of cases. For this reason, this research will be conducted in parallel with an ILD code validation study (ID number 20_000068) to assess the reliability of identifying ILD in primary and secondary care data. Further, we plan to stratify the overall ILD cohort by ILD subtypes.
Preliminary literature review demonstrates incidence and prevalence estimates vary by ILD disease type and geography. The current challenges in ILD diagnoses is due to its various entities and added complexity due to lack of understanding. As well, recent papers have reported an increase in the observed overall ILD cases. Whether this is an actual increase in ILD cases or due to improved coding practices through the years is unknown.
We plan to estimate the incidence and prevalence by overall ILD and by its predefined subtypes. We will also estimate and all-cause mortality in overall ILD cohort and its sub groups.
To comprehend the seriousness of ILD burden in the UK, we aim to enhance ILD evidence using CPRD-HES APC-ONS linked data. We hope that this research will generate epidemiological evidence to fill in the current evidence gaps in the UK.
The primary outcome of this study is to establish the epidemiology of ILD by predefined aetiological subgroups in the UK for the period from 2009 to 2019 defined by incidence, prevalence and all-cause mortality in ILD cohort (overall ILD and its subgroups).
Jennifer Quint - Chief Investigator - Imperial College London
Rikisha Shah Gupta - Corresponding Applicant - Imperial College London
Ann Morgan - Collaborator - Imperial College London
Peter George - Collaborator - Royal Brompton Hospital
HES Admitted Patient Care;ONS Death Registration Data