An Aetiological and Observational Cohort study of Interstitial Lung Abnormalities (ILAs) Including Progressive Fibrosing Phenotype Interstitial Lung Diseases in a Large General Medical Check-up Population (Kumamoto ILA study in Japan) (KILA-J)

ABSTRACT Introduction Interstitial lung abnormalities (ILAs) are subtle or mild parenchymal abnormalities observed in more than 5 % of the lungs on CT scans in patients in whom interstitial lung disease was not previously clinically suspected and is considered. ILA is considered to be partly undeveloped stages of idiopathic pulmonary fibrosis (IPF) or progressive pulmonary fibrosis (PPF). This study aims to clarify the frequency of subsequent IPF or PPF diagnosis, the natural course from the preclinical status of the diseases, and the course after commencing treatment. Methods and analysis This is an ongoing, prospective, multicentre observational cohort study of patients with ILA referred from general health screening facilities with more than 70000 annual attendances. Up to 500 participants will be enrolled annually over 3 years, with 5-year assessments every six months. Treatment intervention including anti-fibrotic agents will be introduced in disease progression cases. The primary outcome is the frequency of subsequent IPF or PPF diagnoses. Additionally, secondary and further endpoints are associated with the efficacy of early therapeutic interventions in cases involving disease progression. Ethics and dissemination This study protocol and informed consent documents have been approved by the Institutional Review Boards of Kumamoto University Hospital (approval number: 2368), Saiseikai Kumamoto Hospital (approval number: 809), and each participating institution. Additionally, written informed consent will be obtained from all participants. Patient recruitment commenced on 20 June 2022. The results will be disseminated through peer-reviewed publications and international conferences. Trial registration number UMIN000045149 Strengths and limitations of this study This is the first prospective, multicentre, observational study to clarify the following points: the aetiological data of patients with ILA from a large general health check-up population the natural course of IPF or PPF from the asymptomatic stage the effects and outcomes of early therapeutic intervention including anti-fibrotic agents for progressive cases of ILA. The limitations of the study: participants missing the regular 6-monthly visits after consenting to participate in the study because of their asymptomatic or the pandemic viral infection.