This study focuses on both hospitalized and outpatient populations. Through a multicenter, retrospective study, it aims to comprehensively characterize:The comorbidity of interstitial lung diseases (ILD) and airway diseases;The comorbidity of ILD with other intrapulmonary diseases;The comorbidity of airway diseases with other intrapulmonary diseases;The comorbidity of ILD and airway diseases with extrapulmonary diseases.Based on these findings, the study seeks to propose classification and diagnostic criteria for ILD and airway disease comorbidities.Additionally, a multicenter, prospective, disease-specific cohort study will be conducted to observe the prognosis of patients with ILD and/or airway diseases, identify prognostic factors, and grade the severity of comorbid conditions based on these factors.Finally, the study will analyze the current state of interventions and the medical costs associated with ILD and airway disease comorbidities through a cost-effectiveness analysis, aiming to propose new strategies for integrated disease management.

This study is divided into two parts, the first part is a multi-center, retrospective study of 9 units in the past 12 months of medical records (10,000 cases) were analyzed; The second part is a multi-center, prospective, observational cohort study. A total of 900 patients with pulmonary interstitial and airway diseases were enrolled, including hospitalized patients, outpatients, and subjects to be confirmed for 2-year follow-up. The total study period was 4 years (2024 December to 2028 November) .

1. A retrospective study was conducted in 9 tertiary hospitals across the country to collect data on cases discharged from respiratory and critical care medicine departments in the previous 12 months (2024 February to February 2025)(about 10,000 cases) , from which cases with a diagnosis of interstitial lung disease, airway disease were screened according to the discharge diagnosis ICD-10 code (disease classification and Code National Clinical Edition 2.0)(Table 1) , the clinical data, chest CT, lung function and intervention measures of the cases were collected to describe the comorbidity and intervention situation of hospitalized pulmonary interstitial and airway diseases in our country, and to put forward the classification and diagnostic criteria of pulmonary interstitial and airway diseases.

   By collecting data on patients with interstitial lung disease and airway disease who had been hospitalized in the respiratory and critical care unit in the previous 12 months at 9 tertiary hospitals, to describe the distribution of diseases, treatment and medical burden of pulmonary interstitial and airway diseases, pulmonary interstitial diseases, airway diseases and other intrapulmonary diseases, pulmonary interstitial diseases, airway diseases and extrapulmonary diseases in hospitalized patients, etc. , the classification and diagnostic criteria of pulmonary interstitial and airway diseases were proposed.

2. A prospective cohort study of comorbidity pulmonary interstitial and airway diseases was conducted in 9 tertiary hospitals across the country. The cohort patients were from three sources, hospitalized in the department of respiratory and critical care medicine, and hospitalized in the department of respiratory and critical care medicine, or outpatient clinics and checkup centers. Part 1 and Part 2: Screening of COPD patients with and without interstitial lung disease, Idiopathic pulmonary fibrosis with and without airway disease, nonspecific interstitial pneumonia with and without airway disease, and pulmonary fibrosis with emphysema in the inpatient and outpatient departments of respiratory and critical care medicine. In the third part, patients with pulmonary interstitial and/or airway diseases requiring respiratory specialist diagnosis in the subject I physical examination population screening, and patients with pulmonary interstitial and/or airway diseases requiring treatment after specialist judgment, were included, the risk factors, clinical information and biological samples of the patients were collected and followed up for 2 years (once every 12 months) . The prognostic information of the patients was collected and the influencing factors related to the prognosis were identified. The severity of comorbidity pulmonary interstitial and airway diseases was graded by analyzing the prognostic factors. By analyzing the intervention status of pulmonary interstitial and airway comorbidity diseases and the cost-effectiveness of medical costs, a new strategy of co-management was proposed. At the same time, it provides data support for the research of the first, fourth, fifth and sixth topic, and provides biological sample support for the third topic.

Clinical data, healthcare resource use, and bio-specimens were collected at baseline and at 2-year follow-up (every 12 months) from 9 Grade III, Class A hospital of respiratory and critical care medicine inpatients, outpatients, and patients with specialty-diagnosed interstitial lung disease and airway disease in the subject 1 physical examination population, to conduct a multi-center, prospective cohort study of comorbidity pulmonary interstitial and airway diseases and identify the influencing factors related to the prognosis of patients with pulmonary interstitial and/or airway diseases. The severity of comorbidity pulmonary interstitial and airway diseases was graded by analyzing the prognostic factors. By analyzing the intervention status of pulmonary interstitial and airway comorbidity diseases and the cost-effectiveness of medical costs, a new strategy of co-management was proposed.

Inclusion Criteria:

1. age between 40-80 years old;
2. inpatients with an admission diagnosis of COPD, Idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, patients with the following diagnoses were screened by chest CT (slice thickness ≤1.5 mm) during hospitalization and by in-hospital or prior pulmonary function;
3. the inpatients could complete pulmonary function and chest CT examination within 1 month after discharge;
4. among outpatients, patients with chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, COPD with pulmonary interstitial abnormalities, idiopathic pulmonary fibrosis with airway lesions, nonspecific interstitial pneumonia with airway lesions, pulmonary fibrosis with emphysema syndrome were diagnosed through chest CT (layer thickness ≤1.5mm) and lung function;
5. provide informed consent.

Exclusion Criteria:

1. expected survival less than 12 months;
2. planned lung transplantation or pneumonectomy within 12 months;
3. pregnant or lactating women.

Among the inpatient or outpatient patients in 9 Grade A hospitals, 900 patients with COPD combined with/uncombined interstitial lung abnormalities, idiopathic pulmonary fibrosis combined with/uncombined airway disease, nonspecific interstitial pneumonia combined with/uncombined airway disease, pulmonary fibrosis combined with emphysema syndrome.