Clinical and Functional Characteristics of Patients with Unclassifiable Interstitial Lung Disease (uILD): Long-Term Follow-Up Data from European IPF Registry (eurIPFreg)

Prevalence and clinical features of progressive pulmonary fibrosis in patients with unclassifiable idiopathic interstitial pneumonia: A post hoc analysis of prospective multicenter registry

BACKGROUND

Idiopathic interstitial pneumonias (IIPs) may remain unclassifiable owing to inadequate, nonspecific, or conflicting clinical, radiological, or histopathological findings despite multidisciplinary discussion (MDD). Unclassifiable IIP (UCIIP) is a heterogeneous disease that can present with progressive pulmonary fibrosis (PPF). This study aimed to investigate the prevalence and clinical features of PPF in patients with UCIIP.

METHODS

In this post hoc analysis of a prospective multicenter registry of 222 patients with IIPs, 71 with UCIIP diagnosed using MDD were enrolled. PPF was defined based on worsening symptoms and radiological and physiological progression using the guideline criteria within 12 months or the criteria from the INBUILD trial within 24 months.

RESULTS

The median age was 72 years, and surgical lung biopsy was performed in 19.7%. Of the 66 patients with adequate follow-up data, 30 (45.5%) met either criterion and were diagnosed with PPF. UCIIP patients with PPF had significantly higher serum surfactant protein-D level and percentage of bronchoalveolar fluid neutrophils, lower %forced vital capacity and %diffusing capacity for carbon monoxide, and a higher proportion of honeycombing on high-resolution computed tomography and desaturation on exertion than those without PPF. Additionally, they had significantly more anti-fibrotic therapy and long-term oxygen therapy, a higher incidence of acute exacerbation, and a poorer prognosis than those without PPF. Cox proportional hazards analysis revealed that PPF was a significant poor prognostic factor, regardless of the criteria.

CONCLUSIONS

PPF is common and associated with poor prognosis in patients with UCIIP. Appropriate evaluation and management of PPF are essential for UCIIP.

Protocol and research program of the European registry and biobank for interstitial lung diseases (eurILDreg)

BACKGROUND AND AIMS

Interstitial lung diseases (ILDs), encompassing both pediatric and adult cases, present a diverse spectrum of chronic conditions with variable prognosis. Despite limited therapeutic options beyond antifibrotic drugs and immunosuppressants, accurate diagnosis is challenging, often necessitating invasive procedures that may not be feasible for certain patients. Drawn against this background, experts across pediatric and adult ILD fields have joined forces in the RARE-ILD initiative to pioneer novel non-invasive diagnostic algorithms and biomarkers. Collaborating with the RARE-ILD consortium, the eurILDreg aims to comprehensively describe different ILDs, analyze genetically defined forms across age groups, create innovative diagnostic and therapeutic biomarkers, and employ artificial intelligence for data analysis.

METHODS

The foundation of eurILDreg is built on a comprehensive parameter list developed and adopted by clinical experts, encompassing over 1,800 distinct parameters related to patient history, clinical examinations, diagnosis, lung function and biospecimen collection. This robust dataset is further enriched with daily assessments captured through the patientMpower app, including handheld spirometry and exercise tests, conducted on approximately 350 patients over the course of a year. This approach involves app-based daily assessments of quality of life, symptom tracking, handheld spirometry, saturation measurement, and the 1-min sit-to-stand test (1-STST). Additionally, pediatric data from the ChILD-EU registry will be integrated into the RARE-ILD Data Warehouse, with the ultimate goal of including a total of 4.000 ILD patients and over 100.000 biospecimen.

DISCUSSION

The collaborative efforts within the consortium are poised to streamline research endeavors significantly, promising to advance patient-centered care, foster innovation, and shape the future landscape of interstitial lung disease research and healthcare practices.

TRIAL REGISTRATION

EurILDreg is registered in the German Clinical Trials Register (DRKS 00028968, 26.07.2022), and eurIPFreg is registered in ClinicalTrials.gov (NCT02951416).

Use of 6-minute walk distance to predict lung transplant-free survival in fibrosing non-IPF interstitial lung diseases

BACKGROUND AND OBJECTIVE

The identification of progression in patients with fibrosing non-idiopathic pulmonary fibrosis (IPF) interstitial lung diseases (ILDs) represents an ongoing clinical challenge. Lung function decline alone may have significant limitations in the detection of clinically significant progression. We hypothesized that longitudinal changes of 6-min walk distance (6MWD) from baseline, simultaneously considered with measures of lung function, may independently predict survival and identifying clinically significant progression of disease.

METHODS

Forced vital capacity (FVC), diffusing lung capacity (DLCO) and 6MWD were considered both at baseline and at 1 year in a discovery cohort (n = 105) and in a validation cohort (n = 138) from different centres. The primary endpoint was lung transplant (LTx)-free survival.

RESULTS

Average follow-up was 3 years in both cohorts. Combined incidence of deaths and LTx was 29% and 21%, respectively. No collinearity and no strong correlations were observed among FVC, DLCO and 6MWD longitudinal changes. While age, gender and BMI were not significant, 6MWD decline ≥24 m predicted LTx-free-survival significantly and independently from FVC and DLCO declines, with high sensitivity and specificity, in both the discovery and the validation cohorts. Although FVC and DLCO declines remained significant predictors of LTx-free survival, 6MWD decline was more accurate than the proposed ATS/ERS/JRS/ALAT functional criteria. Results were confirmed after stratifying patients by baseline FVC.

CONCLUSION

Longitudinal declines of 6MWD are associated with poor survival in fibrosing ILDs across a wide range of baseline severity, with high accuracy. 6MWD longitudinal decline is largely independent from lung function decline and may be integrated into the routine assessment of progression.

Compare three diagnostic criteria of progressive pulmonary fibrosis

Background

In patients with fibrotic interstitial lung disease (ILD), a progressive pulmonary fibrosis (PPF) typically demonstrates worsening respiratory symptoms, lung function decline and continuing fibrosis. The goal of this study was to compare the three different diagnostic criteria of PPF.

Methods

Except for idiopathic pulmonary fibrosis (IPF), all consecutive adult patients with fibrotic ILD were retrospectively examined for the three predefined diagnostic criteria of PPF. The three criteria assessed the disease progression in preceding 6 (0.5-year), 12 (1-year) and 24 (2-year) months respectively. The clinical characteristics, decline in predicted percent of forced vital capacity (FVC%) and survival of three groups were compared, followed by determination of risk factors for mortality.

Results

We identified 246 patients by 0.5-year standard, 154 patients by 1-year standard and 281 patients by 2-year standard. Among them, 95% of patients in 1-year group were also included in 2-year group. The average 1-year decline in FVC% was -1.0%, -2.7%, and -4.1% for 0.5-, 1-, and 2-year group respectively. The 4-year survival rate was 74% in 0.5-year group, 66% in 1-year group, and 62% in 2-year group. In multivariate Cox model, only baseline predicted percent diffusing capacity of the lungs for carbon monoxide (DLCO%) <50% was correlated with mortality, with a hazard ratio of 3.4 (95% CI: 1.1-10.6, P=0.03).

Conclusions

In the current situations, both the 1- and 2-year criterion are the reasonable choice to define PPF both in researches and clinical practice, and DLCO% is an independent predictor for mortality of PPF.

Pulmonary function in children post -SARS-CoV-2 infection: a systematic review and meta-analysis

OBJECTIVE

There are some concerns regarding long-term complications of COVID-19 in children. A systematic review and meta-analysis was performed evaluating the respiratory symptoms and pulmonary function, post-SARS-CoV-2 infection.

METHODS

A systematic search was performed in databases up to 30 March 2023. Studies evaluating respiratory symptoms and pulmonary function after COVID-19 infection in children were selected. The major outcomes were the frequency of respiratory symptoms and the mean of spirometry parameters. A pooled mean with 95% confidence intervals (CIs) was calculated.

RESULTS

A total of 8 articles with 386 patients were included in meta-analysis. Dyspnea, cough, exercise intolerance, and fatigue were the most common symptoms. The meta-mean of forced expiratory volume (FEV1) and forced vital capacity (FVC) was 101.72%, 95% CI= (98.72, 104.73) and 101.31%, 95% CI= (95.44, 107.18) respectively. The meta-mean of FEV1/FVC and Forced expiratory flow at 25 and 75% was 96.16%, 95% CI= (90.47, 101.85) and 105.05%, 95% CI= (101.74, 108.36) respectively. The meta-mean of diffusing capacity for carbon monoxide was 105.30%, 95%CI= (88.12, 122.49). There was no significant difference in spirometry parameters before and after bronchodilator inhalation.

CONCLUSIONS

Despite some clinical respiratory symptoms, meta-results showed no abnormality in pulmonary function in follow-up of children with SARS-CoV-2 infection. Disease severity and asthma background had not confounded this outcome.

Key learnings from the INBUILD trial in patients with progressive pulmonary fibrosis

In a patient with interstitial lung disease (ILD) of known or unknown etiology other than idiopathic pulmonary fibrosis (IPF), progressive pulmonary fibrosis (PPF) is defined by worsening lung fibrosis on high-resolution computed tomography (HRCT), decline in lung function, and/or deterioration in symptoms. The INBUILD trial involved 663 patients with PPF who were randomized to receive nintedanib or placebo. The median exposure to trial medication was approximately 19 months. The INBUILD trial provided valuable learnings about the course of PPF and the efficacy and safety of nintedanib. The relative effect of nintedanib on reducing the rate of forced vital capacity decline was consistent across subgroups based on ILD diagnosis, HRCT pattern, and disease severity at baseline, and between patients who were and were not taking glucocorticoids or disease-modifying anti-rheumatic drugs and/or glucocorticoids at baseline. The adverse events most frequently associated with nintedanib were gastrointestinal, particularly diarrhea, but nintedanib was discontinued in only a minority of cases. The results of the INBUILD trial highlight the importance of prompt detection and treatment of PPF and the utility of nintedanib as a treatment option.

Effect of Nintedanib in Patients with Progressive Pulmonary Fibrosis in Subgroups with Differing Baseline Characteristics

INTRODUCTION

In the INBUILD trial in patients with progressive pulmonary fibrosis other than idiopathic pulmonary fibrosis (IPF), nintedanib slowed the rate of decline in forced vital capacity (FVC; mL/year) over 52 weeks compared with placebo. We assessed the efficacy of nintedanib across subgroups in the INBUILD trial by baseline characteristics.

METHODS

We assessed the rate of decline in FVC over 52 weeks and time to progression of interstitial lung disease (ILD) (absolute decline from baseline in FVC % predicted > 10%) or death over the whole trial in subgroups based on sex, age, race, body mass index (BMI), time since diagnosis of ILD, FVC % predicted, diffusing capacity of the lungs for carbon monoxide (DLco) % predicted, composite physiologic index (CPI), GAP (gender, age, lung physiology) stage, use of anti-acid therapy and use of disease-modifying antirheumatic drugs (DMARDs) at baseline.

RESULTS

The effect of nintedanib versus placebo on reducing the rate of decline in FVC over 52 weeks was consistent across the subgroups by baseline characteristics analysed. Interaction p values did not indicate heterogeneity in the treatment effect between these subgroups (p > 0.05). Over the whole trial (median follow-up time ∼19 months), progression of ILD or death occurred in similar or lower proportions of patients treated with nintedanib than placebo across the subgroups analysed, with no heterogeneity detected between the subgroups.

CONCLUSIONS

In the INBUILD trial, no heterogeneity was detected in the effect of nintedanib on reducing the rate of ILD progression across subgroups based on demographics, ILD severity or use of anti-acid therapy or DMARDs. These data support the use of nintedanib as a treatment for progressive pulmonary fibrosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT02999178.

Validation of Proposed Criteria for Progressive Pulmonary Fibrosis

Rationale: Criteria for progressive pulmonary fibrosis (PPF) have been proposed, but their prognostic value beyond categorical decline in FVC remains unclear. Objectives: To determine whether proposed PPF criteria predict transplant-free survival (TFS) in patients with non-idiopathic pulmonary fibrosis (IPF) forms of interstitial lung disease (ILD). Methods: A retrospective, multicenter cohort analysis was performed. Patients with diagnoses of fibrotic connective tissue disease-associated ILD, fibrotic hypersensitivity pneumonitis, and non-IPF idiopathic interstitial pneumonia from three U.S. centers and one UK center constituted the test and validation cohorts, respectively. Cox proportional hazards regression was used to test the association between 5-year TFS and ⩾10% FVC decline, followed by 13 additional PPF criteria satisfied in the absence of ⩾10% FVC decline. Measurements and Main Results: One thousand three hundred forty-one patients met the inclusion criteria. A ⩾10% relative FVC decline was the strongest predictor of reduced TFS and showed consistent TFS association across cohorts, ILD subtypes, and treatment groups, resulting in a phenotype that closely resembled IPF. Ten additional PPF criteria satisfied in the absence of 10% relative FVC decline were also associated with reduced TFS in the U.S. test cohort, with 6 maintaining TFS associations in the UK validation cohort. Validated PPF criteria requiring a combination of physiologic, radiologic, and symptomatic worsening performed similarly to their stand-alone components but captured a smaller number of patients. Conclusions: An FVC decline of ⩾10% and six additional PPF criteria satisfied in the absence of such decline identify patients with non-IPF ILD at increased risk for death or lung transplantation.

Immunomodulatory treatment in unclassifiable interstitial lung disease: A retrospective study of treatment response

BACKGROUND AND OBJECTIVE

The optimal management of unclassifiable Interstitial lung disease (ILD) remains a challenge. The aim of this study was to describe pulmonary function trajectories for patients treated with immunomodulatory therapy and for untreated patients.

METHODS

Clinical information and treatment data were obtained retrospectively at two ILD centres. Pulmonary function data were analysed using (1) mixed effects linear regression models with and without clinical covariates and (2) propensity score matching using gender, age, physiology (GAP) stage, smoking and presence of ground glass opacities.

RESULTS

Sixty-five percent of the 249 patients included received corticosteroids and/or other immunomodulators. Treated patients had lower forced vital capacity (FVC) (72% vs. 83% predicted) and diffusing capacity for carbon monoxide (DLco) (44% vs. 60% predicted). In mixed effects linear regression, the adjusted change in FVC was -0.22%, [-0.34; -0.11], and -0.15% [-0.28;-0.012] for DLco. The difference in pulmonary function decline between treated and untreated patients was insignificant, -0.082% per month, [-0.28; 0.11], p = 0.10 for FVC and -0.14% per month, [-0.36; 0.079], p = 0.15, for DLco. In propensity score matched analysis, the difference in change in FVC was 0.039% per month, p = 0.12, and for DLco, 0.0085% per month, p = 0.7.

CONCLUSION

The pulmonary function trajectories for treated and untreated patients were parallel, despite treated patients having more severe disease at baseline. The persisting differences between the groups suggest no overall effect, although improvement or stabilization may be seen in some patients. Prospective studies are needed to define subsets of patients with unclassifiable interstitial lung disease and their optimal management.

Meta-Analysis of Effect of Nintedanib on Reducing FVC Decline Across Interstitial Lung Diseases

INTRODUCTION

The effect of nintedanib on slowing the rate of decline in forced vital capacity (FVC) has been investigated in randomized placebo-controlled trials in subjects with idiopathic pulmonary fibrosis (IPF), other progressive fibrosing interstitial lung diseases (ILDs), and ILD associated with systemic sclerosis (SSc-ILD). We assessed the consistency of the effect of nintedanib on the rate of decline in FVC over 52 weeks across four placebo-controlled phase III trials.

METHODS

We used data on FVC decline from the INPULSIS-1 and INPULSIS-2 trials in subjects with IPF, the INBUILD trial in subjects with progressing fibrosing ILDs other than IPF, and the SENSCIS trial in subjects with SSc-ILD. In each trial, the primary endpoint was the annual rate of decline in FVC (mL/year) assessed over 52 weeks. We performed fixed effect and random effects meta-analyses based on the relative treatment effect of nintedanib versus placebo on the rate of decline in FVC (mL/year) over 52 weeks. Heterogeneity of the relative treatment effect of nintedanib across populations was assessed using the I2 statistic, τ2 and corresponding p value from a Q test for heterogeneity.

RESULTS

The combined analysis comprised 1257 subjects treated with nintedanib and 1042 subjects who received placebo. Nintedanib reduced the rate of decline in FVC (mL/year) over 52 weeks by 51.0% (95% CI 39.1, 63.0) compared with placebo. The relative effect (95% CI) was the same using the fixed effect and random effects models. There was no evidence of heterogeneity in the relative treatment effect of nintedanib across the populations studied (I2 = 0%, τ2 = 0, p = 0.93).

CONCLUSIONS

A meta-analysis of data from four placebo-controlled trials demonstrated that nintedanib approximately halved the rate of decline in FVC over 52 weeks across subjects with different forms of pulmonary fibrosis, with no evidence of heterogeneity in its relative treatment effect across patient populations.

Efficacy of Pirfenidone vs. Placebo in Unclassifiable Interstitial Lung Disease, by Surgical Lung Biopsy Status: Data From a post-hoc Analysis

Approximately 12–13% of patients with interstitial lung disease (ILD) are diagnosed with unclassifiable ILD (uILD), often despite thorough evaluation. A recent Phase 2 study (NCT03099187) described a significant effect of pirfenidone vs. placebo on forced vital capacity (FVC) measured by site spirometry in patients with progressive fibrosing uILD (hereafter referred to as the pirfenidone in uILD study). Here, we present the results from a post-hoc analysis of this study to assess patient baseline characteristics and the efficacy of pirfenidone vs. placebo analyzed by surgical lung biopsy (SLB) status. Mean FVC (mL) change over 24 weeks was included as a post-hoc efficacy outcome. Of 253 randomized patients, 88 (34.8%) had a SLB and 165 (65.2%) did not. Baseline characteristics were generally similar between SLB subgroups; however, patients who had a SLB were slightly younger and had a higher 6-min walk distance than those without a SLB. Mean FVC change over 24 weeks for pirfenidone vs. placebo was −90.9 vs. −146.3 mL, respectively, in patients who had a SLB, and 8.2 vs. −85.3 mL, respectively, in patients without a SLB. Overall, the results from the post-hoc analysis identified that pirfenidone may be an effective treatment in progressive fibrosing uILD over 24 weeks, irrespective of SLB status; however, caution should be taken when interpreting these data due to several limitations. There are differences in the treatment effect of pirfenidone between the subgroups that require further pathological and radiological investigation. In this manuscript, we also descriptively compared baseline characteristics from the overall pirfenidone in uILD study population with other uILD populations reported in the literature, with the aim of understanding if there are any similarities or differences within these cohorts. Most baseline characteristics for patients in the pirfenidone in uILD study were within the ranges reported in the literature; however, ranges were wide, highlighting the heterogeneity of uILD populations.

Comorbidities in unclassifiable interstitial lung disease

BACKGROUND

Comorbidities are common in interstitial lung diseases (ILD) and have an important association with survival, but the frequency and prognostic impact of comorbidities in unclassifiable interstitial lung disease (uILD) remains elusive. We aimed to describe the prevalence of comorbidities and assess the impact on survival in patients with uILD. Furthermore, we aimed to identify and characterize potential phenotypes based on clusters of comorbidities and examine their association with disease progression and survival.

METHODS

Incident patients diagnosed with uILD were identified at two ILD referral centers in Denmark and Germany from 2003 to 2018. The diagnosis uILD was based on multidisciplinary team meetings. Clinical characteristics and comorbidities were extracted from ILD registries and patient case files. Survival analyses were performed using Cox regression analyses, disease progression was analyzed by linear mixed effects models, and clusters of comorbidities were analyzed using self-organizing maps.

RESULTS

A total of 249 patients with uILD were identified. The cohort was dominated by males (60%), former (49%) or current (15%) smokers, median age was 70 years, mean FVC was 75.9% predicted, and mean DLCO was 49.9% predicted. One-year survival was 89% and three-year survival was 73%. Eighty-five percent of the patients had ≥ 1 comorbidities, 33% had ≥ 3 comorbidities and 9% had ≥ 5 comorbidities. The only comorbidity associated with excess mortality was dyslipidemia. No association between survival and number of comorbidities or the Charlson comorbidity index was observed. Three clusters with different comorbidities profiles and clinical characteristics were identified. A significant annual decline in FVC and DLCO % predicted was observed in cluster 1 and 2, but not in cluster 3. No difference in mortality was observed between the clusters.

CONCLUSIONS

The comorbidity burden in uILD is lower than reported in other types of ILD and the impact of comorbidities on mortality needs further clarification. Three clusters with distinct comorbidity profiles were identified and could represent specific phenotypes. No difference in mortality was observed between clusters, but slower disease progression was observed in cluster 3. Better understanding of disease behavior and mortality will require further studies of subgroups of uILD with longer observation time.

Predictors of mortality in subjects with progressive fibrosing interstitial lung diseases

Background and objective

Demographic and clinical variables, measured at baseline or over time, have been associated with mortality in subjects with progressive fibrosing interstitial lung diseases (ILDs). We used data from the INPULSIS trials in subjects with idiopathic pulmonary fibrosis (IPF) and the INBUILD trial in subjects with other progressive fibrosing ILDs to assess relationships between demographic/clinical variables and mortality.

Methods

The relationships between baseline variables and time‐varying covariates and time to death over 52 weeks were analysed using pooled data from the INPULSIS trials and, separately, the INBUILD trial using a Cox proportional hazards model.

Results

Over 52 weeks, 68/1061 (6.4%) and 33/663 (5.0%) subjects died in the INPULSIS and INBUILD trials, respectively. In the INPULSIS trials, a relative decline in forced vital capacity (FVC) >10% predicted within 12 months (hazard ratio [HR] 3.77) and age (HR 1.03 per 1‐year increase) were associated with increased risk of mortality, while baseline FVC % predicted (HR 0.97 per 1‐unit increase) and diffusing capacity of the lungs for carbon monoxide (DLCO) % predicted (HR 0.77 per 1‐unit increase) were associated with lower risk. In the INBUILD trial, a relative decline in FVC >10% predicted within 12 months (HR 2.60) and a usual interstitial pneumonia‐like fibrotic pattern on HRCT (HR 2.98) were associated with increased risk of mortality, while baseline DLCO % predicted (HR 0.95 per 1‐unit increase) was associated with lower risk.

Conclusion

These data support similarity in the course of lung injury between IPF and other progressive fibrosing ILDs and the value of FVC decline as a predictor of mortality.

We assessed relationships between baseline and time‐varying factors and mortality over 52 weeks in 1061 subjects with idiopathic pulmonary fibrosis (IPF) and 663 subjects with other progressive fibrosing interstitial lung diseases (ILDs). Our findings support similarity in the course of IPF and ILD and an association between decline in forced vital capacity and mortality.

Integration of transbronchial cryobiopsy into multidisciplinary board decision: a single center analysis of one hundred consecutive patients with interstitial lung disease

Background

Transbronchial cryobiopsy in the evaluation of patients with interstitial lung diseases (ILD) is expected to reduce the need for surgical lung biopsy (SLB).

Objective

To evaluate the diagnostic value of cryobiopsy in combination with bronchoalveolar lavage (BAL), radiologic and clinical data in patients with ILD.

Methods

Between 08/15 and 01/20 patients with ILD underwent cryobiopsy if they: did not have (i) an usual interstitial pneumonia (UIP)-pattern on CT, (ii) predominant ground-glass opacities suggesting alveolitis, (iii) findings suggestive of sarcoidosis on CT, or if they had (i) a CT showing UIP-pattern, but had findings suggesting alternative diagnosis than idiopathic pulmonary fibrosis (IPF), or (ii) had previous non-diagnostic conventional transbronchial forceps biopsy. Histological findings were integrated into the multidisciplinary team discussion (MDTD) and a diagnostic consensus was sought.

Results

One hundred patients underwent cryobiopsy. In 88/100 patients, cryobiopsy was representative with diagnostic findings in 45/88 and non-specific histological findings in 43/88 patients. In 25/43 with non-specific findings, a consensus diagnosis was reached after MDTD integrating BAL, radiologic and clinical data; eight of the remaining 18 patients with non-specific findings were referred to SLB. In 12/100 patients cryobiopsy was not representative and three of these patients were also referred to SLB. In 7/11 patients (64%) SLB was diagnostic. Complications of cryobiopsy included pneumothorax (14%) and locally controlled bleeding (24%).

Conclusions

The diagnostic yield of cryobiopsy was 70%:45% of cryobiopsies were diagnostic based on histology alone and an additional 25% provided non-specific, but valuable findings allowing a consensus diagnosis after MDTD. Our data demonstrate that the diagnostic value of cryobiopsy is high if combined with BAL, radiologic and clinical data.

Unclassifiable, or simply unclassified interstitial lung disease?

PURPOSE OF REVIEW

Unclassifiable interstitial lung disease (ILD) comprises a subset of ILDs which cannot be classified according to the current diagnostic framework. This is a likely a heterogeneous group of diseases rather than a single entity and it is poorly defined and hence problematic for prognosis and therapy.

RECENT FINDINGS

With increased treatment options for progressive fibrosing ILD it is increasingly relevant to correctly categorise ILD.

SUMMARY

This review article will summarise the definition and reasons for a diagnosis of unclassifiable ILD, the current management options and possible future approaches to improve diagnosis and differentiation within this broad subset. Finally, we will describe the implications of the labelling of unclassifiable ILD in clinical practice and research and whether the term 'unclassified' should be used, implying a less definitive diagnosis.

A contemporary practical approach to the multidisciplinary management of unclassifiable interstitial lung disease

Fibrotic interstitial lung diseases (ILDs) frequently have nonspecific and overlapping clinical and radiological features, resulting in approximately 10-20% of patients with ILD lacking a clear diagnosis and thus being labelled with unclassifiable ILD. The objective of this review is to describe how patients with unclassifiable ILD should be evaluated and what impact specific clinical, radiological, and histopathological features may have on management decisions, focusing on patients with a predominantly fibrotic phenotype. We highlight recent data that have suggested an increasing role for antifibrotic medications in a variety of fibrotic ILDs, but justify the ongoing importance of making an accurate ILD diagnosis given the benefit of immunomodulatory therapies in many patient populations. We provide a practical approach to support management decisions that can be used by clinicians and tested by clinical researchers, and further identify the need for additional research to support a rational and standardised approach to the management of patients with unclassifiable ILD.

[Interstitial lung disease associated with connective tissue disease]

Interstitial lung disease (ILD) is the most frequent organ manifestation in rheumatic autoimmune disease. Depending on the underlying autoimmune disease, differently pronounced affections of small airways, interstitial parenchyma, and vessels are found. The group of rheumatic autoimmune diseases mainly includes connective tissue diseases (CTDs), also known as collagen vascular diseases, such as rheumatoid arthritis (RA), systemic sclerosis, (SSc), systemic lupus erythematosus, primary Sjögren's syndrome, idiopathic inflammatory myositis (IIM), and interstitial pneumonia with autoimmune features (IPAF). Frequency and manifestations of parenchymal lung disorders are described clinically, radiologically, and morphologically in these entities. For the precise diagnosis and for the differentiation between the wide range of parenchymal disorders with known possible cause or with unknown origin, also called unclassifiable or idiopathic interstitial pneumonias (IIPs), high resolution computed tomography (HRCT) findings represent the diagnostic gold standard. A transbronchial biopsy, surgical biopsy, or cryobiopsy will be used in unclassifiable findings to confirm a definitive histological confirmation. A precise diagnosis of these ILDs is crucial since the different pathologies that encompass ILD have different therapeutic options. In this sense, the participation of a pneumologist, rheumatologist, radiologist, and pathologist become essential in the multidisciplinary evolution of ILD.