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)

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 limitations of the study: ### Competing Interest Statement KIchi, HI, TJ, and TS received lecture fees from the Nippon Boehringer Ingelheim Co. Ltd. N.T., T. Handa, and T. Hirai have received research grants from FUJIFILM Corporation. T. Handa is in the employment of the Collaborative Research Laboratory funded by Teijin Pharma Co., Ltd ### Funding Statement This work is supported by Nippon Boehringer Ingelheim Co. Ltd. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: the Institutional Review Boards of Kumamoto University Hospital (approval number: 2368), Saiseikai Kumamoto Hospital (approval number: 809) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Although this study has been ongoing now, all data produced in the study will be available upon reasonable request to the authors.