The benefits of a rapid diagnostic primary care circuit for interstitial lung disease

Abstract

Interstitial lung diseases (ILDs) are complex rare diseases that associate a delay in diagnosis and eventually poor prognosis. Early and accurate diagnosis could be crucial. This study aimed to evaluate the feasibility and benefits of a rapid diagnostic circuit for ILD. A training program for ILD identification and a direct referral diagnostic circuit to the ILD Unit of University Hospital of Bellvitge were established in primary care centers in the southern metropolitan area of Barcelona (Spain). ILD patients were diagnosed and followed-up until study completion, death or lung transplantation. Diagnostic, therapeutic and prognostic outcomes were compared to patients referred through the common circuit during the same period of time. Of 123 patients referred directly from the primary care, 112 had ILD. The most common diagnosis were idiopathic pulmonary fibrosis and fibrotic hypersensitivity pneumonitis. The main reasons for suspecting ILD were interstitial radiological features (74%) and abnormal lung auscultation (67%). Eighteen patients were asymptomatic. Compared with patients referred through the common circuit, there was a statistically significant reduction in the time from symptom onset to diagnosis (6 vs. 22.1 months, p < 0.01) and in the percentage of fibrosing ILD (55.9 vs 63.9%, p 0.36). Although patients from rapid circuit were older, they had better forced vital capacity and diffusing capacity for carbon monoxide at diagnosis (p 0.04) and lung biopsies were performed more frequently. More patients were elegible for lung transplant. Identifying potential patients with fibrotic ILD through rapid circuit working with primary care physicians is feasible and useful.

Introduction

Interstitial lung diseases (ILDs) represent a group of rare and complex conditions of both known and unknown origin. Fibrotic ILDs may progress despite standard treatment, leading to respiratory failure and early mortality¹. The common fibrotic ILD is idiopathic pulmonary fibrosis (IPF), which is characterized by chronic, progressive and irreversible scarring of the lung. Main symptoms and signs of IPF and non-IPF progressive pulmonary fibrosis (PPF) include dyspnea, dry cough, inspiratory crackles, and finger clubbing^2,3. A confident diagnosis is challenging and requires expert multidisciplinary teams which are not available in all hospitals^2,4,5. The natural history varies considerably between patients but involves a decline in lung function and quality of life, that eventually leads to death⁶.

A delay of 1-3 years between symptom onset and diagnosis is frequently observed in fibrotic ILDs, mainly due to the limited awareness of primary care physicians about these types of rare diseases^5–10. Delayed diagnosis of IPF and other fibrotic ILDs is associated with worse survival^5,7,11,12. Furthermore, misdiagnosis of other respiratory diseases, such as asthma, and the futility of most empirical treatments initiated before diagnosis impact on the patient’s emotional state and healthcare resources. Finally, early intervention is crucial to improve ILD prognosis. Avoiding risk factors or identified causes and initiating antifibrotic drugs when necessary may modify the natural history of the disease, reducing mortality, and even preventing irreversible changes in induced fibrotic ILDs^12–16. Although there are no specific biomarkers with predictive diagnostic or prognostic value, several studies are currently testing molecular, genetic, and epigenetic markers that will be useful even in the early stages of the disease^9,10. Therefore, early diagnosis and optimal therapeutic management of fibrotic ILDs are more relevant than ever^4,5,9.

In this regard, lung auscultation for velcro-like crackles, which are strongly associated with the presence of pulmonary fibrosis, has been proposed as a feasible and sensitive measure to improve early detection³. However, most cases report a patient’s journey that starts receiving symptomatic treatment, including inhalers, in primary care centers¹⁷. After worsening despite treatment, patients are referred to a pulmonologist, who performs additional respiratory tests^5–7. Once ILD is identified and the patient continues to worsen, referral to an ILD Unit at a tertiary center allows for multidisciplinary diagnosis^{3–5,17–19}. Therefore, definitive diagnosis and therapeutic management usually take more than a year^6,7.

Although the time required for ILD diagnosis varies considerably by geographic area, delays occur at every stage of the diagnostic process, even after raising awareness about these rare diseases among the general population and healthcare workers^20–22. Therefore, considering the relevance of existing rapid diagnostic pathways for oncological diseases to reduce diagnostic delay, a pilot program for rapid ILD diagnosis was established and analyzed in collaboration with primary care centers in our area.

Methods

Population and study design

Our multicenter, observational, retrospective study included consecutive patients with newly diagnosed ILD between 2012 and 2015, with follow-up until 2022 at the ILD Unit of University Hospital of Bellvitge (HUB). Diagnosis and treatment were performed according to the American Thoracic Society/European Respiratory Society criteria by the multidisciplinary committee (MDT)². This study was approved by the HUB Ethics Committee (PR413/18). It was conducted in accordance with the ethical principles of the Declaration of Helsinki and local legislation laws. Informed consent was obtained from each participant by the study investigator prior to data collection.

Initially, a training program for clinical suspicion and identification of ILD patients was performed in 10 primary care centers staffed by general practitioners (GPs) focused on respiratory diseases. Chest radiologists from these centers were connected to the ILD radiological team at the HUB. As online clinical and radiological network was established. All ILD patients diagnosed through this circuit were recruited and followed-up until study completion, death or lung transplantation. Outcomes were compared with those of patients referred through the common patient diagnostic circuit during the same period. These patients were referred from 12 hospitals for which the HUB is the referral center for complex diagnostic and therapeutic procedures, including rare respiratory rare diseases.

The rapid diagnostic circuit was established through an ILD Unit’s email account that was reviewed every weekday. In addition, GPs faxed the case referral and information.

If a primary care radiologist identified the case after evaluating a chest x-ray or high-resolution computed tomography (HRCT), they contacted the GP to activate the rapid diagnostic referral circuit (Fig. 1).

Fig. 1.

Rapid circuit diagnostic algorithm for patients with ILD that avoids the typical ILD patient journey. There are four types of patients with a suspected diagnosis of ILD in Primary Care. Subclinical cases are patients with few respiratory symptoms, patients at risk of developing ILD (for example, due to family history or environmental or occupational exposures) and incidental cases (diagnosis of ILD by chance, extension study, abdominal CT scan and suspicion of ILD in thoracic sections, etc). Finally, there are clinical cases, which are the most frequent (those with respiratory symptoms such as dry cough and/or dyspnea). All these patients should undergo a through physical examination to rule out the presence of finger clubbing, complete respiratory semiology to rule out the presence of crackles on auscultation, and a detailed medical history. Subsequently, complementary examinations are performed, such as a chest X-ray and/or chest CT scan, spirometry and, if ILD is diagnosed in Primary Care, the patient is referred is made to the Tertiary Care Centre, specifically to the ILD Unit, to confirm and study the diagnosis of ILD through the Multidisciplinary Expert Committee. Once the patient is diagnosed with ILD, depending on the severity, they will continue to be monitored at the Expert Unit or may be referred back to Primary Care.

The common respiratory diagnostic circuit included email contact with the ILD Unit and an administrative referral by fax. Cases were referred by pulmonologists, internal medicine physicians, rheumatologists, thoracic surgeons, and emergency physicians from various hospitals.

In both diagnostic pathways (rapid and standard), all patients received a report of their first visit to the HUB’s Specialized ILD Unit, and subsequent visits were recorded in their medical records. At each visit, the requested diagnostic test, the results of the test performed, the diagnosis from the ILD Unit’s Multidisciplinary Committee, the therapeutic strategy to be followed, and the start date of antifibrotic treatment (if prescribed) were recorded. This information is stored in the computer system of our hospital and primary care centers, as they are part of the same computer system.

Asymptomatic cases were not included in the analyses of time since symptom onset. Missing or uncertain onset dates were excluded from the analyses.

Collected data

Baseline demographic and clinical characteristics were collected at diagnosis, including age, gender, smoking status/history, occupational and environmental exposures, respiratory symptoms and signs (crackles and nail clubbing), time to symptom onset, comorbidities, radiological high-resolution computed tomography (HRCT) pattern, final diagnosis, and treatment received. HRCT findings and radiological pattern were interpreted according to the recommendations of the Fleischner Society nomenclature commitee²³. HRCT patterns are retrospective reports. Chest HRCT images were reviewed and graded by radiologists from the Multidisciplinary Committee using a semiquantitative scoring scale for fibrotic-like changes. The lungs were evaluated in five different regions: aortic arch, carina, between the carina and the inferior pulmonary veins, inferior pulmonary veins, and 1 cm above the diaphragm. The extent of fibrotic-like changes was visually quantified in each area, and the overall percentage was calculated by averaging the fibrotic scores of the 10 areas. Fibrotic ILD was defined radiologically as the presence of fibrosing features on chest HRCT that exceeded 5% of the total lung area. The lung function characteristics, such as forced vital capacity (FVC) and diffusing capacity of the lung for carbon monoxide (DLCO), 6-minute walk test (6MWT) and oxygen desaturation were also included. During the follow-up, clinical, functional and radiological data and use of antifibrotic treatment were recorded. Missing or uncertain start dates were excluded from the analysi (transcription error).

Mortality, survival and lung transplantation were also recorded. Data from patients referred using both referral process (rapid and common diagnostic circuit) were compared.

Both cohorts were generated at the same time, with identical access to diagnostics and antifibrotics. All patients with suspected or identified ILD sent through both circuits were evaluated and diagnosed by the same ILD team. All of them were included in the study, even the minority of cases with a final MDT diagnosis different than ILD. The non-ILD referrals were always reached by email for the feedback about the final diagnosis (in both circuits).

Statistical analysis

Categorical data are described as frequency and percentages, and differences were evaluated using chi-squared test or Fisher’s exact test when required. For descriptive analysis, continuous and normally distributed variables are expressed as mean and standard deviation (SD). To assess differences in outcomes between the rapid diagnostic circuit and common diagnostic circuit, we used multivariate regression models.

Differences in continuous variables were analyzed with ANOVA tests or Student’s t test, or their corresponding non-parametrical tests when required (Kruskal-Wallis and Mann-Whitney U tests). The time origin of the survival analyses is set at the time of confirmed ILD diagnosis. Time to event data (time to lung transplantation and/or death) were analyzed using Kaplan-Meier survival analysis and Cox proportional hazard regression for multivariable analyses, ensuring that comparisons between groups were more accurate and free of bias. A p-value < 0.05 was considered statistically significant. Data were analyzed by using SPSS 27 (SPSS, IBM Corp). The recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) initiative were followed²⁴.

Results

Patient features at diagnosis

A total of 726 new patients were referred to the HUB ILD Unit between 2012 and 2015. Of the 123 patients referred directly from primary care, 112 patients (91.05%) had ILD and 11 had other respiratory diseases such as cylindrical bronchiectasis or pulmonary edema (Fig. 1). These patients showed a mean age of 66.3 years (IQR 9.5), and 55.9% (SD 5.92) had fibrotic ILD. The main reasons for suspecting ILD in primary care were interstitial radiological features (74%) and auscultation of lung crackles (67%). A chest HRCT was performed before arrival to the ILD Unit in 81.05% patients. No invasive procedures were performed during the patient’s journey. The time from symptom onset (when present) to diagnosis was 6 months (SD 5) (Fig. 2). No respiratory symptoms were identified in 18 patients, although 2 of them presented with fibrosing ILD. The main diagnoses were IPF and fibrotic hypersensitivity pneumonitis (fHP) (Table 1). The median FVC was 89.61% (IQR 17.23) and DLCO was 68.72% (SD 17.89). Up to 34.82% cases showed oxygen desaturation below 90% in the 6MWT. The predominant radiological patterns on HRCT were indeterminate usual interstitial pneumonia (UIP) (41.90%) and probable UIP (36.61%). Thirty-four patients (30.35%) underwent bronchoscopy and surgical lung biopsy was necessary to reach a diagnosis in 43 patients (38.39%) (Table 1). Interstitial lung abnormality (ILA) was identified in 3 patients, of whom 2 progressed to fibrotic ILD during follow-up.

Fig. 2.

Time from onset of symptoms to diagnosis in the Rapid Diagnostic Circuit and Common Diagnostic Circuit.

Table 1.

Characteristics of patients in the rapid referral circuit and common referral circuit at the time of diagnosis.

	Rapid diagnostic circuit (n 112)	Common diagnostic circuit (n 564)	p-value
ILD Subtypes (n, %)
IPF	27 (24.13%)	98 (17.38%)	0.291
HP	18 (16.14%)	86 (15.25%)	0.645
CTD-ILD	14 (12.55%)	80 (14.18%)	0.833
OP	8 (7.11)	74 (13.12%)	0.247
Sarcoidosis	15 (13.48%)	59 (10.46%)	0.661
Occupational	7 (6.33%)	36 (6.38%)	0.764
Drug/Radiation-induced ILD	4 (3.69%)	6 (1.06%)	0.628
Unclassifiable	13 (11.57%)	78 (13.83%)	0.733
Others	1 (0.98%)	6 (1.06%)	0.861
ILA	3 (2.74%)	8 (1.42%)	0.878
Age (years), median (IQR)	66.3 (9.55)	62.3 (3.18)	0.035*
Gender (male), n (%)	62 (60.78%)	379 (67.19%)	0.488
Fibrosing ILD, mean (SD)	55.9% (5.92)	63.9% (3.67)	0.046*
FVC percentage of predicted, median (IQR)	89.61 (17.23)	76.14 (15.78)	0.008*
DLCO percentage of predicted, mean ± SD	68.72 ±17.89	56.26 ± 18.45	0.013*
Desaturation on 6MWT below 90%, n (%)	39 (34.82%)	327 (57.98%)	0.021*
Chest HRCT pattern, n (%)
Definite UIP	24 (21.43%)	247 (43.79%)	0.016*
Probable UIP	41 (36.61%)	169 (29.96%)	0.202
Indeterminate UIP	47 (41.96%)	148 (26.24%)	0.019*
Surgical lung biopsy, n (%)	43 (38.39)	186 (32.97)	0.004*
Time (months) from onset of symptoms to diagnosis, mean (SD)	6 (5.31)	22.1 (9.92)	<0.001*
Asymptomatic, n (%)	18 (16.07)	62 (10.99)	0.082
Antifibrotic treatment (only in IPF), n (%)	21 (18.75)	85 (15.07)	0.622
Lung transplant median % (95% CI)	11.61 (5.69, 17.53)	8.51 (6.22, 10.81)	<0.001*
Transplant-free survival at 7 years follow-up, median % (95% CI)	57.14 (48,66.3)	42.73 (38.65, 46.81)	0.043*

IPF idiopathic pulmonary fibrosis, HP hypersensitivity pneumonitis, CTD-ILD connective tissue disease associated interstitial lung disease, OP organizing pneumonia, ILA interstitial lung abnormalities, FVC forced vital capacity, DLCO diffusing capacity for carbon monoxide, HRCT high resolution computed tomography, UIP usual interstitial pneumonia, 6MWT 6-minute walk test, IQR interquartile range, SD standard deviation, 95% CI 95% confidence interval.

Of the 603 patients referred through the common circuit, 39 (6.46%) had other non-ILD respiratory diseases such as cylindrical bronchiectasis, pulmonary edema or asthma and 564 ILD patients were diagnosed and followed-up. The median age was 62.3 years and the majority were men (67.19%). Most patients presented with fibrotic ILD (63.9%) and 43.79% had a definite UIP pattern on chest HRCT. The main diagnoses were IPF and fibrotic hypersensitivity pneumonitis (fHP). Most patients were referred after ILD was identified on chest HRCT (87.21%) and 79% had crackles on auscultation. Sixty-two patients had no respiratory symptoms, and of these, 4 (6.45%) had fibrosing ILD. The median FVC was 76.14% (IQR 15.78) and DLCO was 56.26% (SD 18.45%). A total of 57.98% cases showed oxygen desaturation below 90% in 6MWT. The time from symptom onset (when present) to diagnosis was 22.1 (SD 9.9) months (Fig. 1). During the patient’s journey, chest HRCT was performed at least once in all patients, and 210 (37.23%) before the final diagnostic procedures at the ILD Unit. The diagnoses were variable but the proportion of each ILD did not differ from the rapid referral circuit cohort (Table 1). Interstitial lung abnormalities (ILAs) were initially identified in 8 patients, and 5 of them progressed to ILD during follow-up. Surgical lung biopsy was performed for diagnosis in 32.97% of patients.

The main differences between the Rapid Diagnostic Circuit and the Common Diagnostic Circuit were the referral modality, the radiological report, the evaluation prior to the first appointment in the Specialized ILD Unit, the time until the first ILD appointment and the people involved in each diagnostic process (Fig. 3 and Table 2).

Fig. 3.

ILD Diagnostic Circuit Workflow Diagram. Main differences between both diagnostic circuits.

Table 2.

ILD Diagnostic Circuit Workflow Diagram. Main differences between both diagnostic circuits.

	Rapid Diagnostic Circuit	Common Diagnostic Circuit
Trigger	Radiological interstitial findings, velcro crackles, symptoms/signs	Radiological interstitial findings, velcro crackles, symptoms/signs
Referral mode	Dedicated email to the ILD Unit and hospital form and appointment	Generic hospital form and appointment
Radiology	Joint PC–HUB consensus read	Routine report from referral center
Work-up before first ILD appointment	Chest X-Ray or HRCT, spirometry, medical history	Full pre-evaluation (chest HRCT, medical history, pulmonary functional test, blood tests, +/- fibrobroncoscopy)
Timeline	First ILD appointment ≤ 1 month	First ILD appointment ≤ 3 months
Actors	PC physician, radiologists, ILD Specialized Unit secretary, MDT	Different physicians (usually more than one) and hospitals, radiologists, general administrative officer

PC primary care, ILD interstitial lung disease, MDT multidisciplinary committee.

The delay in diagnosis (time from symptom onset) and the number of non-diagnostic tests during the patient’s journey were significantly lower in those patients referred from primary care centers (Fig. 1 and Table 1).

Disease outcomes

1. FVC progression

   Regarding the subgroup of patients with IPF who presented symptoms at the time of diagnosis, patients from the rapid diagnostic circuit had a higher FVC than those from the common circuit. The time elapsed from of symptom onset to diagnosis was defined as the “FVC diagnostic pitfall”:

   $$\mathit{FVC\; diagnostic\; pitfall}=\frac{FVC\left(\%\right)\mathit{onset\; of\; symptoms}-FVC\left(\%\right)\mathit{at\; diagnosis}}{\nabla FVC\left(\%\right)/\mathit{year}}$$

   $\nabla$ : decrease

   Figure 4, shows the progressive decline in predicted FVC (%) over a 7-year follow-up period for patients with IPF and respiratory symptoms can be observed. We highlight the area referred to as the “Diagnostic FVC pitfall,” which is defined as the interval between the onset of symptoms and the time of diagnosis, delineated by the annual progressive decline of the predicted FVC. All patients, both those from the common diagnostic circuit and those from the rapid diagnostic circuit, start with an initial FVC of 100% at the time of diagnosis, ensuring a fair comparison between the two groups. This would be the ideal situation: patients could be diagnosed at this time with this FVC value, which would be at symptom onset. However, what we have observed in our clinical practice is that patients in the common diagnostic circuit are diagnosed with a lower FVC compared to those in the rapid diagnostic circuit.

2. Impact of antifibrotic therapy and lung transplantation

   No significant difference was observed in the percentage of IPF patients treated with antifibrotics between the two groups. However, antifibrotic drugs were only available in a clinical trial (nintedanib) or for compassionate use (pirfenidone) for selected IPF patients at the time of referral (Table 1).

   The use of Cox proportional hazards regression allowed for adequate adjustment for baseline differences between the two diagnostic circuits (such as age, FVC/DLCO and the presence of defined UIP patterns). After this adjustment, the rapid circuit approach was associated with a lower need for transplantation and improved survival in patients with pulmonary fibrosis. Furthermore, the rapid circuit approach was associated with a significantly higher rate of surgical lung biopsies performed.

   Lung transplantation was more common in patients in the rapid referral group (11.61 vs 8.51%, p < 0.001) (Table 1).

3. Transplant-Free Survival Outcomes

Fig. 4.

evolutionary decrease in predicted FVC over 7 years of follow-up of patients with IPF in the rapid diagnostic circuit and in the common diagnostic circuit.

The differences in 7-year transplant-free survival between both groups were statistically significant (57.14 and 42.73%, (p = 0.043) (Table 1, Fig. 5).

Fig. 5.

Transplant- free survival at 7 years follow-up in the rapid and common diagnostic circuit.

Discussion

The results of our study suggest that a rapid referral circuit from primary care centers to an ILD Unit is feasible and improves ILD patient’s journey by reducing the delay in diagnosis and the number of additional tests performed, the latter compared to the standard pathway used in Spain and other countries⁵. Furthermore, it allows to identify a greater number of patients with fibrotic ILDs at early stages and is associated with a higher likelihood of lung transplantation and better survival after transplantation.

Different strategies have been suggested to achieve early diagnosis of ILDs, including awareness among primary care physicians, lung cancer screening programs, and the use of artificial intelligence (AI) to analyze computed tomography (CT) images^25–27. An early diagnosis of IPF may lead to timely pharmacological and non-pharmacological treatment and, therefore, better disease outcomes²⁸. Furthermore, the European Commission seek to achieve sustainable proposed actions and implementations into national plans and strategies for rare diseases such as ILDs. However, ILDs can be difficult to diagnose in early stages due to overlapping symptoms with other more common conditions that may be attributed to ageing, smoking or cardiovascular conditions²⁹. Moreover, patients with early disease may present minimal symptoms or subtle clinical signs. Patients with IPF frequently endure a significant delay to diagnosis^22,30. Furthermore, an accurate diagnosis requires a specialized multidisciplinary ILD team^2,4,31, available in some tertiary centers^5,18,32. The pivotal role played by primary care physicians play in the early diagnosis of diseases highlights the need for educational interventions to raise awareness of ILDs. This, in turn, could result in rapid referral of patients to specialized centers and in on-going dialogue between pulmonologists and primary care physicians during patient follow-up and at the end of life. A retrospective study conducted in two specialist ILD clinics from UK and Ireland investigated patients’ outcomes in relation to the time from primary care visit to ILD specialist center referral³³. The study showed that patients evaluated at an ILD clinic within 12 months had a longer time to death and a longer duration of antifibrotic medication compared with those evaluated later³³. Silva et al. evaluated primary care physicians’ awareness of the major ILD subtypes, including IPF. Their questionnaire assessed respondents’ degree of awareness of the basic diagnosis and management of the main ILD conditions in five healthcare centers. Participants performed acceptably on sections related to hypersensitivity pneumonitis, connective tissue disease associate with ILD, sarcoidosis and drug-induced ILD; but, their level of awareness of IPF was considered poor³⁴. Several models of rapid diagnostic circuits for ILD have been proposed^10,35,36.

A rapid diagnosis more frequently identifies early or mild- stages ILD cases, allowing for an optimal therapeutic approach that may impact on the natural history of the disease^37,38. An analysis from the Australian IPF registry found that patients with IPF with mild physiological impairment (FVC ≥ 80%) had better survival than patients with moderate-to-severe disease (FVC < 80%). However, the overall rate of disease progression was comparable, suggesting that better survival in early stages simply reflects an earlier point in the natural history of IPF³⁹. Other studies have indicated that patients with IPF in mild functional stages experience fewer episodes of acute exacerbation than those with advanced disease^29,40. However, preserved FVC may reflect different types of IPF patients and is not sufficient to indicate early IPF. This observation may have prognostic and therapeutic implications when considering the initiation of antifibrotic treatment or evaluating lung transplantation. Decreased DLCO or definite UIP pattern of diagnosis is associated with a poor prognosis⁴⁰. Therefore, IPF patients with preserved FVC would allow a broader spectrum of treatment options^41–46.

Early detection of pulmonary fibrosis allows the disease to be identified at a stage when symptoms may not yet be pronounced, or functional impairment may be minimal. This early stage is often characterized by subtle radiological changes and mild functional impairment, which may not yet have a significant impact on the patient’s quality of life. Detecting the disease at this point can significantly shift the “time zero”—the reference point from which disease progression is measured.

Therefore, early detection of pulmonary fibrosis holds great promise for altering the natural course of the disease, promoting slower progression and improving transplant-free survival. However, the interpretation of these benefits must consider potential biases and the heterogeneous nature of the disease. Continued research and refined clinical strategies are essential to fully harness the advantages of early diagnosis, ensuring that patients receive optimal care tailored to their specific disease profiles.

The main limitations of this work are associated with the retrospective nature of the study, which impacts the comparison between both groups. However, the diagnostic, treatment and follow-up process were the same for all patients due to the standardized protocols of the ILD Unit in clinical practice. It is important to note that between 2012 and 2015, the availability of antifibrotics was limited, which significantly influenced clinical practices at the time. This restriction on access to antifibrotic treatments meant that therapeutic strategies during that period did not include the same options currently available, thus preventing implicit parity with contemporary practices.

Another limitation of the study is the difficulty in extrapolating these results to regions or countries that do not have established rapid diagnostic circuit or do not have the option of training GPs and radiologists in specific diseases or conditions. Nevertheless, the established training program and rapid diagnostic circuit are feasible, so an international validation would be possible for implementing these procedures in ILD clinical practice.

Conclusions

Early identification of fibrotic ILDs is possible through a rapid referral circuit, a training program, and networking with primary care centers. Furthermore, rapid referral from primary care centers can improve the patient’s journey, optimize healthcare resources, and tend to improve survival rates.

Author contributions

Guadalupe Bermudo (GB) has received for research projects from Boehringer Ingelheim, Hoffmann La Roche, not related with the present study.Pilar Rivera-Ortega (PRO) has received speaker and consultations fees from Boehringer Ingelheim, The Limbic, Chiesi, Cipla, Tecnofarma, and Hoffmann La Roche, none of them related to this study. PRO has also received research honoraria from Boehringer Ingelheim, Hoffmann La Roche, CSL Behring, FibroGen, Vicore Pharma AB, Gilead Sciences, Galecto, and Chiesi; not related to the present study.V.Vicens-Zygmunt (VVZ) has received for research projects from Boehringer Ingelheim, not related with the present study.María Molina-Molina (MM) has received grants and fees for scientific advice, not related with the present study, from Boehringer Ing, Ferrer, Janssen, Roche, Raffo.B.Del Río (BDR), S.Bolivar (SB), E.Serra (ES), F.Ferrer (FF), R.Llatjós (RL), F. Rivas (FR), R.López-Lisbona (RLL), L.García (LG), S.Santos (SS) and P.Luburich (PL); have nothing to disclose.

Data Availability

The datasets generated and analyzed during the current study are not publicly available due to contain sensitive personal information of hospital patients and are subject to strict confidentiality agreements and data protection laws. However, anonymized data may be accessed by qualified researchers upon reasonable request and with approval from the University Hospital Bellvitge Ethics Committee (PR413/18).

Competing interests

The authors declare no competing interests.