Organizational intervention that coordinates and bundles all required ILD follow-up procedures into a single structured "one-day" visit. For patients with established ILD on antifibrotic and/or immunosuppressive therapy, the intervention pre-schedules pulmonary function tests, laboratory monitoring, imaging when indicated, pharmacy consultation, nursing assessment, and medical visits within the same day. When clinically necessary, rheumatology or internal medicine consultations are integrated into the same coordinated circuit. The intervention does not introduce new tests or treatments and does not modify hospital waiting-list rules; it only reorganizes the timing and consolidation of existing follow-up procedures to reduce overall time burden.

This measure calculates the total economic impact on the healthcare system during the follow-up pathway. It includes:

1. Direct Clinical Costs: Outpatient visits, multidisciplinary committee reviews, and monitoring tests (CT scans, lung function tests, and biopsies) based on standard hospital billing rates.
2. Operational Costs: Administrative staff time dedicated to the coordination and scheduling of the circuit.
3. Inefficiency Costs: Opportunity costs derived from non-attended appointments (no-shows), missed or incomplete follow-up procedures requiring rescheduling, and unscheduled emergency visits.

All values are calculated in Euros (€). Higher scores indicate higher healthcare resource utilization and lower operational efficiency

Estimated CO₂-equivalent emissions generated by patient and caregiver travel and healthcare resource use during the follow-up cycle. Emissions are calculated from reported travel distance, transport mode and number of companions using validated emission factors.

The EQ-5D-5L is a standardized instrument for measuring generic health status. It consists of a descriptive system covering 5 dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) and the EQ Visual Analogue Scale (EQ-VAS). The 5 dimensions are scored on 5 levels (1=no problems to 5=extreme problems). The EQ-VAS records the patient's self-rated health on a scale from 0 (worst health) to 100 (best health). Results are reported as an index score (ranging from <0 to 1, where 1 is perfect health) and the VAS score. Higher scores in the index and VAS indicate better quality of life.

The K-BILD is a validated 15-item health-related quality of life questionnaire specifically designed for patients with interstitial lung disease (ILD). It assesses three domains: psychological, breathlessness and activities, and chest symptoms. Each item is scored on a 7-point Likert scale. A total score and three domain scores are calculated. Scores are transformed to a range of 0 to 100, where 100 represents the best health status and 0 the worst. A higher score reflects a better quality of life related to the respiratory disease.

The GAD-7 is a validated 7-item self-report questionnaire used to screen for and measure the severity of generalized anxiety. Each item is scored on a 4-point Likert scale (0=Not at all to 3=Nearly every day). The total score ranges from 0 to 21. Established severity thresholds are: 0-4 minimal, 5-9 mild, 10-14 moderate, and 15-21 severe anxiety. Higher scores indicate greater anxiety severity.

The PHQ-9 is a validated 9-item self-report questionnaire used to screen for and measure the severity of depression. Each item is scored on a 4-point Likert scale (0=Not at all to 3=Nearly every day). The total score ranges from 0 to 27. Established severity thresholds are: 0-4 minimal, 5-9 mild, 10-14 moderate, 15-19 moderately severe, and 20-27 severe depression. A score of >=10 is commonly used as the threshold for clinically significant depression. Higher scores indicate greater depressive symptom severity.

The CFS is a 9-point scale used to assess the overall level of fitness or frailty in older adults or patients with chronic conditions. It is based on clinical judgment of the patient's mobility, activity, and independence in daily living. The scale ranges from 1 (Very Fit) to 9 (Terminally Ill). A score of ≥5 is generally considered to represent frailty. Higher scores indicate a higher degree of clinical frailty.

A scale used to detect social risk or social isolation. It evaluates 5 domains: family situation, economic status, housing, social relationships, and social support. Each item is scored 1 to 5. The total score ranges from 5 to 25. Higher scores reflect greater social vulnerability (10-14: social risk; ≥15: social problem).

The Oslo-3 is a brief 3-item instrument that assesses the level of perceived social support. It evaluates the number of close confidants, the sense of concern from others, and the ease of obtaining practical help from neighbors. The total score ranges from 3 to 14 and is categorized as: 3-8 poor support, 9-11 moderate support, and 12-14 strong support. Higher scores indicate greater perceived social support.

A study-specific 7-item screening questionnaire, developed in collaboration with the Hospital Social Work Department, designed to identify patients who may benefit from social work assessment. The instrument evaluates: 1) Prior contact with social services (informative), 2) Awareness of available public resources for disability or chronic disease, 3) Digital literacy barriers affecting appointment management, 4) Need for home support or difficulty leaving the home, 5) Disability or dependency recognition status, 6) Perceived caregiver overburden, and 7) Patient willingness to receive social work consultation. Referral to social work is offered when any item triggers a positive response, or when the Gijon Scale indicates social risk (>=12), the Oslo-3 indicates poor social support (<=8), or the CBI-15 indicates high caregiver burden (>=25). The proportion of patients meeting referral criteria, the effective referral rate, and the specific unmet needs identified will be reported.

The PREM-Patient is a study-specific, self-administered 11-item questionnaire developed by the investigators to assess the patient's healthcare experience in the ILD follow-up pathway. As an ad hoc instrument, it evaluates 11 quality domains: 1) Clarity, 2) Coordination, 3) Accessibility (staff contact), 4) Logistical Efficiency, 5) Process Agility, 6) Prioritization (accompained visits), 7) Economic Impact, 8) Life Balance, 9) Information Redundancy, 10) Safety, and 11) Clinical Support. Each item is scored on a Likert scale from 0 (Completely Disagree) to 10 (Completely Agree). The total score is the sum of the 11 items (score ranges from 0 to 110), where higher scores indicate a more optimized and patient-centered experience. A 12th item assesses Global Satisfaction separately.

The PREM-Caregiver is a study-specific, self-administered 11-item questionnaire developed by the investigators to assess the healthcare experience of the caregiver in the ILD follow-up pathway. This ad hoc instrument evaluates 11 quality domains: 1) Clarity, 2) Coordination, 3) Accessibility (staff contact), 4) Logistical Efficiency, 5) Process Agility, 6) Prioritization (accompained visits), 7) Economic Impact, 8) Life Balance, 9) Information Redundancy, 10) Safety, and 11) Clinical Support. Each item is scored on a Likert scale from 0 to 10. The total score ranges from 0 to 110, where higher scores indicate a more optimized experience and lower treatment burden for the family unit. A 12th item assesses Global Satisfaction separately.

Assessed only for participants with a primary caregiver who provides independent informed consent for this specific evaluation.

The CBI-15 is a validated 15-item multidimensional questionnaire that assesses caregiver burden across five domains: time-dependence burden (3 items), personal life burden (3 items), physical burden (3 items), social burden (3 items), and emotional burden (3 items). Each item is scored on a 5-point Likert scale (0=Not at all disruptive to 4=Very disruptive). The total score ranges from 0 to 60. A total score of >=25 has been identified as a cut-off point to discriminate caregivers with probable mental disorder (sensitivity 70.6%, specificity 70.7%). Higher scores indicate greater perceived burden. The Spanish version validated by Vazquez et al. (Int J Environ Res Public Health 2019;16:217) is used. Assessed only for participants with a primary caregiver who provides independent informed consent for this specific evaluation.

The PREM-Clinician is a study-specific, self-administered 11-item questionnaire developed by the investigators to assess the professional experience of all staff involved in the ILD follow-up pathway, including clinicians and other involved healthcare professionals (including nursing, pharmacy, and social work). As an ad hoc instrument, it evaluates 11 quality domains: 1) Inter-professional Coordination, 2) Administrative Burden, 3) Protocol Clarity, 4) Process Agility, 5) Information Provided to Patient, 6) Caregiver Integration, 7) Operational Sustainability, 8) Resource Efficiency, 9) Perceived Patient/Family Satisfaction, 10) Clinical Safety, and 11) Multidisciplinary Support. Each item is scored on a Likert scale (0-10). Total score: 0 to 110. Higher scores indicate a more optimized and collaborative workflow. A 12th item assesses Global Satisfaction separately.

A single-item measure in which the patient rates their overall impression of how the organization of the follow-up visit compared to their expectations, using a 7-point Likert scale (1=Much better than expected to 7=Much worse than expected). This measure serves as an anchor to determine the minimal clinically important difference (MCID) of the study-specific PREMs. Lower scores indicate a more favorable impression of the follow-up pathway organization.

A single-item measure in which the primary caregiver rates their overall impression of how the organization of their family member's follow-up visit compared to their expectations, using a 7-point Likert scale (1=Much better than expected to 7=Much worse than expected). Lower scores indicate a more favorable impression. Assessed only for participants with a primary caregiver who provides independent informed consent.

A single-item measure in which each healthcare professional involved in the ILD follow-up pathway rates their overall impression of the pathway's organizational quality compared to their prior expectations, using a 7-point Likert scale (1=Much better than expected to 7=Much worse than expected). Lower scores indicate a more favorable professional impression of the coordinated circuit.

Pre-planned exploratory analysis measuring the variation in the primary outcome (total follow-up time burden) and key secondary outcomes stratified by sociodemographic determinants -- including socioeconomic status (Gijon Socio-familial Evaluation Scale), perceived social support (Oslo-3 Social Support Scale), unmet social needs (Social Work Screening Questionnaire), ethnicity, gender of both the patient and the primary caregiver, language proficiency, educational level, and geographical distance to the hospital. This analysis evaluates the magnitude of potential disparities and the intervention's capacity to ensure equitable access to follow-up care regardless of the patient's sociodemographic profile.