Biological Age, Chronological Age and Survival in Pulmonary Fibrosis: A Causal Mediation Analysis.

RATIONALE: Accelerated biological aging has been implicated in the development of interstitial lung disease (ILD) and other diseases of aging but remains poorly understood. OBJECTIVES: To identify plasma proteins that mediate the relationship between chronological age and survival association in patients with ILD. METHODS: Causal mediation analysis was performed to identify plasma proteins that mediated the chronological age-survival relationship in an idiopathic pulmonary fibrosis (IPF) discovery cohort. Proteins mediating this relationship after adjustment for false discovery were advanced for testing in an independent ILD validation cohort and explored in a chronic obstructive pulmonary disease (COPD) cohort. A proteomic-based measure of biological age was constructed and survival analysis performed assessing the impact of biological age and peripheral blood telomere length on the chronological age-survival relationship. RESULTS: Twenty-two proteins mediated the chronological age-survival relationship after adjustment for false discovery in the IPF discovery cohort (n=874), with nineteen remaining significant mediators of this relationship in the ILD validation cohort (n=983) and one mediating this relationship in the COPD cohort. Latent transforming growth factor beta binding protein 2 and ectodysplasin A2 receptor showed the strongest mediation across cohorts. A proteomic measure of biological age completely attenuated the chronological age-survival association and better discriminated survival than chronological age. Results were robust to adjustment for peripheral blood telomere length, which did not mediate the chronological age-survival relationship. CONCLUSIONS: Molecular measures of aging completely mediate the relationship between chronological age and survival, suggesting that chronological age has no direct effect on ILD survival.

Molecular Endotypes of Idiopathic Pulmonary Fibrosis: A Latent Class Analysis of Two Multicenter Observational Cohorts.

Rationale: Idiopathic pulmonary fibrosis (IPF) causes irreversible fibrosis of the lung parenchyma. While antifibrotic therapy can slow IPF progression, treatment response is variable. There exists a critical need to develop a precision medicine approach to IPF. Objective: To identify and validate biologically driven molecular endotypes of IPF. Methods: Latent class analysis (LCA) was independently performed in prospectively recruited discovery (n=875) and validation (n=347) cohorts. Twenty-five plasma biomarkers associated with fibrogenesis served as class-defining variables. The association between molecular endotype and 4-year transplant-free survival was tested using multivariable Cox regression adjusted for baseline confounders. Endotype-dependent differential treatment response to future antifibrotic exposure was then assessed in a pooled cohort of patients naïve to antifibrotic therapy at time of biomarker measurement (n=555). Results: LCA independently identified two latent classes in both cohorts (p<0.0001). WAP four-disulfide core domain protein 2 (WFDC2) was the most important determinant of class membership across cohorts. Membership in Class 2 was characterized by higher biomarker concentrations and higher risk of death or transplantation (discovery: HR 2.02 [95% CI 1.64-2.48]; p<0.001; validation: HR 1.95 [1.34-2.82]; p<0.001). In pooled analysis, significant heterogeneity in treatment effect was observed between endotypes (pinteraction=0.030), with a favorable antifibrotic response in Class 2 (HR 0.64 [0.45-0.93]; p=0.018) but not in Class 1 (HR 1.19 [0.77-1.84]; p=0.422). Conclusions: In this multicohort study, we identified two novel molecular endotypes of IPF with divergent clinical outcomes and response to antifibrotics. Pending further validation, these endotypes could enable a precision medicine approach for future IPF clinical trials.

Deep Learning Classification of Usual Interstitial Pneumonia Predicts Outcomes.

Rationale: Computed tomography (CT) enables noninvasive diagnosis of usual interstitial pneumonia (UIP), but enhanced image analyses are needed to overcome the limitations of visual assessment. Objectives: Apply multiple instance learning (MIL) to develop an explainable deep learning algorithm for prediction of UIP from CT and validate its performance in independent cohorts. Methods: We trained an MIL algorithm using a pooled dataset (n = 2,143) and tested it in three independent populations: data from a prior publication (n = 127), a single-institution clinical cohort (n = 239), and a national registry of patients with pulmonary fibrosis (n = 979). We tested UIP classification performance using receiver operating characteristic analysis, with histologic UIP as ground truth. Cox proportional hazards and linear mixed-effects models were used to examine associations between MIL predictions and survival or longitudinal FVC. Measurements and Main Results: In two cohorts with biopsy data, MIL improved accuracy for histologic UIP (area under the curve, 0.77 [n = 127] and 0.79 [n = 239]) compared with visual assessment (area under the curve, 0.65 and 0.71). In cohorts with survival data, MIL-UIP classifications were significant for mortality (n = 239, mortality to April 2021: unadjusted hazard ratio, 3.1; 95% confidence interval [CI], 1.96-4.91; P < 0.001; and n = 979, mortality to July 2022: unadjusted hazard ratio, 3.64; 95% CI, 2.66-4.97; P < 0.001). Individuals classified as UIP positive by the algorithm had a significantly greater annual decline in FVC than those classified as UIP negative (-88 ml/yr vs. -45 ml/yr; n = 979; P < 0.01), adjusting for extent of lung fibrosis. Conclusions: Computerized assessment using MIL identifies clinically significant features of UIP on CT. Such a method could improve confidence in radiologic assessment of patients with interstitial lung disease, potentially enabling earlier and more precise diagnosis.

Machine Learning of Plasma Proteomics Classifies Diagnosis of Interstitial Lung Disease.

RATIONALE: Distinguishing connective tissue disease associated interstitial lung disease (CTD-ILD) from idiopathic pulmonary fibrosis (IPF) can be clinically challenging. OBJECTIVES: Identify proteins that separate and classify CTD-ILD from IPF patients. METHODS: Four registries with 1247 IPF and 352 CTD-ILD patients were included in analyses. Plasma samples were subjected to high-throughput proteomics assays. Protein features were prioritized using Recursive Feature Elimination (RFE) to construct a proteomic classifier. Multiple machine learning models, including Support Vector Machine, LASSO regression, Random Forest (RF), and imbalanced-RF, were trained and tested in independent cohorts. The validated models were used to classify each case iteratively in external datasets. MEASUREMENT AND MAIN RESULTS: A classifier with 37 proteins (PC37) was enriched in biological process of bronchiole development and smooth muscle proliferation, and immune responses. Four machine learning models used PC37 with sex and age score to generate continuous classification values. Receiver-operating-characteristic curve analyses of these scores demonstrated consistent Area-Under-Curve 0.85-0.90 in test cohort, and 0.94-0.96 in the single-sample dataset. Binary classification demonstrated 78.6%-80.4% sensitivity and 76%-84.4% specificity in test cohort, 93.5%-96.1% sensitivity and 69.5%-77.6% specificity in single-sample classification dataset. Composite analysis of all machine learning models confirmed 78.2% (194/248) accuracy in test cohort and 82.9% (208/251) in single-sample classification dataset. CONCLUSIONS: Multiple machine learning models trained with large cohort proteomic datasets consistently distinguished CTD-ILD from IPF. Identified proteins involved in immune pathways. We further developed a novel approach for single sample classification, which could facilitate honing the differential diagnosis of ILD in challenging cases and improve clinical decision-making.

The impact of antifibrotic use on long-term clinical outcomes in the pulmonary fibrosis foundation registry.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a devastating interstitial lung disease (ILD) with a high mortality rate. The antifibrotic medications pirfenidone and nintedanib have been in use since 2014 for this disorder and are associated with improved rate of lung function decline. Less is known about their long-term outcomes outside of the clinical trial context. METHODS: The Pulmonary Fibrosis Foundation Patient Registry was used for this study. Patients with an IPF diagnosis made within a year of enrollment were included. The treated group was defined as patients receiving either pirfenidone or nintedanib for at least 180 days. The untreated group did not have any record of antifibrotic use. Demographic data, comorbidities, serial lung function, hospitalization, and vital status data were collected from the registry database. The primary outcomes were transplant-free survival, time to first respiratory hospitalization, and time to 10% absolute FVC decline. Time-to-event analyses were performed utilizing Cox proportional hazards models and the log-rank test. Model covariates included age, gender, smoking history, baseline lung function, comorbidities, and oxygen use. RESULTS: The registry contained 1212 patients with IPF; ultimately 288 patients met inclusion criteria for the treated group, and 101 patients were designated as untreated. Patients treated with antifibrotics were significantly younger (69.8 vs. 72.6 years, p = 0.008) and less likely to have smoked (61.1% ever smokers vs. 72.3% never smokers, p = 0.04). No significant differences were seen in race, gender, comorbidities, or baseline pulmonary function between groups. The primary outcome of transplant-free survival was not significantly different between the two groups (adjusted HR 0.799, 95% CI 0.534-1.197, p = 0.28). Time to respiratory hospitalization was significantly shorter in the treated group (adjusted HR 2.12, 95% CI 1.05-4.30, p = 0.04). No significant difference in time to pulmonary function decline was seen between groups. CONCLUSIONS: This multicenter study demonstrated 63% of newly diagnosed IPF patients had continuous antifibrotic usage. Antifibrotics were not associated with improved transplant-free survival or pulmonary function change but was associated with an increased hazard of respiratory hospitalization. Future studies should further investigate the role of antifibrotic therapy in clinically important outcomes in real-world patients with IPF and other progressive ILDs.

Proteomic Biomarkers of Survival in Idiopathic Pulmonary Fibrosis.

RATIONALE: Idiopathic pulmonary fibrosis (IPF) causes progressive lung scarring and high mortality. Reliable and accurate prognostic biomarkers are urgently needed. OBJECTIVE: To identify and validate circulating protein biomarkers of IPF survival. METHODS: High-throughput proteomic data were generated using prospectively collected plasma samples from patients with IPF from the Pulmonary Fibrosis Foundation Patient Registry (discovery cohort) and the Universities of California-Davis, Chicago, and Virginia (validation cohort). Proteins associated with three-year transplant-free survival (TFS) were identified using multivariable Cox proportional hazards regression. Those associated with TFS after adjustment for false discovery in the discovery cohort were advanced for testing in the validation cohort, with proteins maintaining TFS association with consistent effect direction considered validated. After combining cohorts, functional analyses were performed, and machine learning used to derive a proteomic signature of TFS. MAIN RESULTS: Of 2921 proteins tested in the discovery cohort (n=871), 231 were associated with differential TFS. Of these, 140 maintained TFS association with consistent effect direction in the validation cohort (n=355). After combining cohorts, validated proteins with strongest TFS association were latent-transforming growth factor beta-binding protein 2 (HR 2.43, 95% CI 2.09-2.82), collagen alpha-1(XXIV) chain (HR 2.21; 95% CI 1.86-2.39) and keratin 19 (HR 1.60; 95% CI 1.47-1.74). In decision curve analysis, a proteomic signature of TFS outperformed a similarly derived clinical prediction model. CONCLUSIONS: In largest proteomic investigation of IPF outcomes performed to date, we identified and validated 140 protein biomarkers of TFS. These results shed important light on potential drivers of IPF progression.

PCSK6 and Survival in Idiopathic Pulmonary Fibrosis.

Rationale: Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by limited treatment options and high mortality. A better understanding of the molecular drivers of IPF progression is needed. Objectives: To identify and validate molecular determinants of IPF survival. Methods: A staged genome-wide association study was performed using paired genomic and survival data. Stage I cases were drawn from centers across the United States and Europe and stage II cases from Vanderbilt University. Cox proportional hazards regression was used to identify gene variants associated with differential transplantation-free survival (TFS). Stage I variants with nominal significance (P < 5 × 10-5) were advanced for stage II testing and meta-analyzed to identify those reaching genome-wide significance (P < 5 × 10-8). Downstream analyses were performed for genes and proteins associated with variants reaching genome-wide significance. Measurements and Main Results: After quality controls, 1,481 stage I cases and 397 stage II cases were included in the analysis. After filtering, 9,075,629 variants were tested in stage I, with 158 meeting advancement criteria. Four variants associated with TFS with consistent effect direction were identified in stage II, including one in an intron of PCSK6 (proprotein convertase subtilisin/kexin type 6) reaching genome-wide significance (hazard ratio, 4.11 [95% confidence interval, 2.54-6.67]; P = 9.45 × 10-9). PCSK6 protein was highly expressed in IPF lung parenchyma. PCSK6 lung staining intensity, peripheral blood gene expression, and plasma concentration were associated with reduced TFS. Conclusions: We identified four novel variants associated with IPF survival, including one in PCSK6 that reached genome-wide significance. Downstream analyses suggested that PCSK6 protein plays a potentially important role in IPF progression.

Tobacco smoking is associated with combined pulmonary fibrosis and emphysema and worse outcomes in interstitial lung disease.

Tobacco smoking is an established cause of pulmonary disease whose contribution to interstitial lung disease (ILD) is incompletely characterized. We hypothesized that compared with nonsmokers, subjects who smoked tobacco would differ in their clinical phenotype and have greater mortality. We performed a retrospective cohort study of tobacco smoking in ILD. We evaluated demographic and clinical characteristics, time to clinically meaningful lung function decline (LFD), and mortality in patients stratified by tobacco smoking status (ever vs. never) within a tertiary center ILD registry (2006-2021) and replicated mortality outcomes across four nontertiary medical centers. Data were analyzed by two-sided t tests, Poisson generalized linear models, and Cox proportional hazard models adjusted for age, sex, forced vital capacity (FVC), diffusion capacity of the lung for carbon monoxide (DLCO), ILD subtype, antifibrotic therapy, and hospital center. Of 1,163 study participants, 651 were tobacco smokers. Smokers were more likely to be older, male, have idiopathic pulmonary fibrosis (IPF), coronary artery disease, CT honeycombing and emphysema, higher FVC, and lower DLCO than nonsmokers (P < 0.01). Time to LFD in smokers was shorter (19.7 ± 20 mo vs. 24.8 ± 29 mo; P = 0.038) and survival time was decreased [10.75 (10.08-11.50) yr vs. 20 (18.67-21.25) yr; adjusted mortality HR = 1.50, 95%CI 1.17-1.92; P < 0.0001] compared with nonsmokers. Smokers had 12% greater odds of death for every additional 10 pack yr of smoking (P < 0.0001). Mortality outcomes remained consistent in the nontertiary cohort (HR = 1.51, 95%CI = 1.03-2.23; P = 0.036). Tobacco smokers with ILD have a distinct clinical phenotype strongly associated with the syndrome of combined PF and emphysema, shorter time to LFD, and decreased survival. Smoking prevention may improve ILD outcomes.NEW & NOTEWORTHY Smoking in ILD is associated with combined pulmonary fibrosis and emphysema and worse clinical outcomes.

Treatable traits: a comprehensive precision medicine approach in interstitial lung disease.

Interstitial lung disease (ILD) is a diverse group of inflammatory and fibrotic lung conditions causing significant morbidity and mortality. A multitude of factors beyond the lungs influence symptoms, health-related quality of life, disease progression and survival in patients with ILD. Despite an increasing emphasis on multidisciplinary management in ILD, the absence of a framework for assessment and delivery of comprehensive patient care poses challenges in clinical practice. The treatable traits approach is a precision medicine care model that operates on the premise of individualised multidimensional assessment for distinct traits that can be targeted by specific interventions. The potential utility of this approach has been described in airway diseases, but has not been adequately considered in ILD. Given the similar disease heterogeneity and complexity between ILD and airway diseases, we explore the concept and potential application of the treatable traits approach in ILD. A framework of aetiological, pulmonary, extrapulmonary and behavioural and lifestyle treatable traits relevant to clinical care and outcomes for patients with ILD is proposed. We further describe key research directions to evaluate the application of the treatable traits approach towards advancing patient care and health outcomes in ILD.

Telomere length and immunosuppression in non-idiopathic pulmonary fibrosis interstitial lung disease.

BACKGROUND: Studies suggest a harmful pharmacogenomic interaction exists between short leukocyte telomere length (LTL) and immunosuppressants in idiopathic pulmonary fibrosis (IPF). It remains unknown if a similar interaction exists in non-IPF interstitial lung disease (ILD). METHODS: A retrospective, multicentre cohort analysis was performed in fibrotic hypersensitivity pneumonitis (fHP), unclassifiable ILD (uILD) and connective tissue disease (CTD)-ILD patients from five centres. LTL was measured by quantitative PCR for discovery and replication cohorts and expressed as age-adjusted percentiles of normal. Inverse probability of treatment weights based on propensity scores were used to assess the association between mycophenolate or azathioprine exposure and age-adjusted LTL on 2-year transplant-free survival using weighted Cox proportional hazards regression incorporating time-dependent immunosuppressant exposure. RESULTS: The discovery and replication cohorts included 613 and 325 patients, respectively. In total, 40% of patients were exposed to immunosuppression and 22% had LTL <10th percentile of normal. fHP and uILD patients with LTL <10th percentile experienced reduced survival when exposed to either mycophenolate or azathioprine in the discovery cohort (mortality hazard ratio (HR) 4.97, 95% CI 2.26-10.92; p<0.001) and replication cohort (mortality HR 4.90, 95% CI 1.74-13.77; p=0.003). Immunosuppressant exposure was not associated with differential survival in patients with LTL ≥10th percentile. There was a significant interaction between LTL <10th percentile and immunosuppressant exposure (discovery pinteraction=0.013; replication pinteraction=0.011). Low event rate and prevalence of LTL <10th percentile precluded subgroup analyses for CTD-ILD. CONCLUSION: Similar to IPF, fHP and uILD patients with age-adjusted LTL <10th percentile may experience reduced survival when exposed to immunosuppression.

Integrative multi-omics analysis reveals novel idiopathic pulmonary fibrosis endotypes associated with disease progression.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is characterized by the accumulation of extracellular matrix in the pulmonary interstitium and progressive functional decline. We hypothesized that integration of multi-omics data would identify clinically meaningful molecular endotypes of IPF. METHODS: The IPF-PRO Registry is a prospective registry of patients with IPF. Proteomic and transcriptomic (including total RNA [toRNA] and microRNA [miRNA]) analyses were performed using blood collected at enrollment. Molecular data were integrated using Similarity Network Fusion, followed by unsupervised spectral clustering to identify molecular subtypes. Cox proportional hazards models tested the relationship between these subtypes and progression-free and transplant-free survival. The molecular subtypes were compared to risk groups based on a previously described 52-gene (toRNA expression) signature. Biological characteristics of the molecular subtypes were evaluated via linear regression differential expression and canonical pathways (Ingenuity Pathway Analysis [IPA]) over-representation analyses. RESULTS: Among 232 subjects, two molecular subtypes were identified. Subtype 1 (n = 105, 45.3%) and Subtype 2 (n = 127, 54.7%) had similar distributions of age (70.1 +/- 8.1 vs. 69.3 +/- 7.6 years; p = 0.31) and sex (79.1% vs. 70.1% males, p = 0.16). Subtype 1 had more severe disease based on composite physiologic index (CPI) (55.8 vs. 51.2; p = 0.002). After adjusting for CPI and antifibrotic treatment at enrollment, subtype 1 experienced shorter progression-free survival (HR 1.79, 95% CI 1.28,2.56; p = 0.0008) and similar transplant-free survival (HR 1.30, 95% CI 0.87,1.96; p = 0.20) as subtype 2. There was little agreement in the distribution of subjects to the molecular subtypes and the risk groups based on 52-gene signature (kappa = 0.04, 95% CI= -0.08, 0.17), and the 52-gene signature risk groups were associated with differences in transplant-free but not progression-free survival. Based on heatmaps and differential expression analyses, proteins and miRNAs (but not toRNA) contributed to classification of subjects to the molecular subtypes. The IPA showed enrichment in pulmonary fibrosis-relevant pathways, including mTOR, VEGF, PDGF, and B-cell receptor signaling. CONCLUSIONS: Integration of transcriptomic and proteomic data from blood enabled identification of clinically meaningful molecular endotypes of IPF. If validated, these endotypes could facilitate identification of individuals likely to experience disease progression and enrichment of clinical trials. TRIAL REGISTRATION: NCT01915511.

Expert consensus on the management of systemic sclerosis-associated interstitial lung disease.

BACKGROUND: Systemic sclerosis (SSc) is a rare, complex, connective tissue disorder. Interstitial lung disease (ILD) is common in SSc, occurring in 35-52% of patients and accounting for 20-40% of mortality. Evolution of therapeutic options has resulted in a lack of consensus on how to manage this condition. This Delphi study was initiated to develop consensus recommendations based on expert physician insights regarding screening, progression, treatment criteria, monitoring of response, and the role of recent therapeutic advances with antifibrotics and immunosuppressants in patients with SSc-ILD. METHODS: A modified Delphi process was completed by pulmonologists (n = 13) and rheumatologists (n = 12) with expertise in the management of patients with SSc-ILD. Panelists rated their agreement with each statement on a Likert scale from - 5 (complete disagreement) to + 5 (complete agreement). Consensus was predefined as a mean Likert scale score of ≤ - 2.5 or ≥ + 2.5 with a standard deviation not crossing zero. RESULTS: Panelists recommended that all patients with SSc be screened for ILD by chest auscultation, spirometry with diffusing capacity of the lungs for carbon monoxide, high-resolution computed tomography (HRCT), and/or autoantibody testing. Treatment decisions were influenced by baseline and changes in pulmonary function tests, extent of ILD on HRCT, duration and degree of dyspnea, presence of pulmonary hypertension, and potential contribution of reflux. Treatment success was defined as stabilization or improvement of signs or symptoms of ILD and functional status. Mycophenolate mofetil was identified as the initial treatment of choice. Experts considered nintedanib a therapeutic option in patients with progressive fibrotic ILD despite immunosuppressive therapy or patients contraindicated/unable to tolerate immunotherapy. Concomitant use of nintedanib with MMF/cyclophosphamide can be considered in patients with advanced disease at initial presentation, aggressive ILD, or significant disease progression. Although limited consensus was achieved on the use of tocilizumab, the experts considered it a therapeutic option for patients with early SSc and ILD with elevated acute-phase reactants. CONCLUSIONS: This modified Delphi study generated consensus recommendations for management of patients with SSc-ILD in a real-world setting. Findings from this study provide a management algorithm that will be helpful for treating patients with SSc-ILD and addresses a significant unmet need.

Idiopathic Pulmonary Fibrosis (an Update) and Progressive Pulmonary Fibrosis in Adults: An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline.

Background: This American Thoracic Society, European Respiratory Society, Japanese Respiratory Society, and Asociación Latinoamericana de Tórax guideline updates prior idiopathic pulmonary fibrosis (IPF) guidelines and addresses the progression of pulmonary fibrosis in patients with interstitial lung diseases (ILDs) other than IPF. Methods: A committee was composed of multidisciplinary experts in ILD, methodologists, and patient representatives. 1) Update of IPF: Radiological and histopathological criteria for IPF were updated by consensus. Questions about transbronchial lung cryobiopsy, genomic classifier testing, antacid medication, and antireflux surgery were informed by systematic reviews and answered with evidence-based recommendations using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. 2) Progressive pulmonary fibrosis (PPF): PPF was defined, and then radiological and physiological criteria for PPF were determined by consensus. Questions about pirfenidone and nintedanib were informed by systematic reviews and answered with evidence-based recommendations using the GRADE approach. Results:1) Update of IPF: A conditional recommendation was made to regard transbronchial lung cryobiopsy as an acceptable alternative to surgical lung biopsy in centers with appropriate expertise. No recommendation was made for or against genomic classifier testing. Conditional recommendations were made against antacid medication and antireflux surgery for the treatment of IPF. 2) PPF: PPF was defined as at least two of three criteria (worsening symptoms, radiological progression, and physiological progression) occurring within the past year with no alternative explanation in a patient with an ILD other than IPF. A conditional recommendation was made for nintedanib, and additional research into pirfenidone was recommended. Conclusions: The conditional recommendations in this guideline are intended to provide the basis for rational, informed decisions by clinicians.

Lung function trajectory in progressive fibrosing interstitial lung disease.

BACKGROUND: Proposed criteria for progressive fibrosing interstitial lung disease (PF-ILD) have been linked to increased mortality risk, but lung function trajectory after satisfying individual criteria remains unknown. Because survival is rarely employed as the primary end-point in therapeutic trials, identifying PF-ILD criteria that best predict subsequent change in forced vital capacity (FVC) could improve clinical trial design. METHODS: A retrospective, multicentre longitudinal cohort analysis was performed in consecutive patients with fibrotic connective tissue disease-associated ILD (CTD-ILD), chronic hypersensitivity pneumonitis and idiopathic interstitial pneumonia at three US centres (test cohort) and one UK centre (validation cohort). 1-year change in FVC after satisfying proposed PF-ILD criteria was estimated using joint modelling. Subgroup analyses were performed to determine whether results varied across key subgroups. RESULTS: 1227 patients were included, with CTD-ILD predominating. Six out of nine PF-ILD criteria were associated with differential 1-year change in FVC, with radiological progression of fibrosis, alone and in combination with other features, associated with the largest subsequent decline in FVC. Findings varied significantly by ILD subtype, with CTD-ILD demonstrating little change in FVC after satisfying most PF-ILD criteria, while other ILDs showed significantly larger changes. Findings did not vary after stratification by radiological pattern or exposure to immunosuppressant therapy. Near-term change in FVC after satisfying proposed PF-ILD criteria was heterogeneous depending on the criterion assessed and was strongly influenced by ILD subtype. CONCLUSIONS: These findings may inform future clinical trial design and suggest ILD subtype should be taken into consideration when applying PF-ILD criteria.

Inhalational exposures in patients with fibrotic interstitial lung disease: Presentation, pulmonary function and survival in the Canadian Registry for Pulmonary Fibrosis.

BACKGROUND AND OBJECTIVE: Inhalational exposures are a known cause of interstitial lung disease (ILD), but little is understood about their prevalence across ILD subtypes and their relationship with pulmonary function and survival. METHODS: Patients with fibrotic ILD were identified from the multicentre Canadian Registry for Pulmonary Fibrosis. Patients completed questionnaires regarding ILD-related occupational and environmental exposures. The relationship between exposures and the outcomes of baseline age, gender, family history, pulmonary function and survival was analysed using linear and logistic regression models, linear mixed-effect regression models and survival analysis using multivariable Cox proportional hazards along with the log-rank test. RESULTS: There were 3820 patients included in this study, with 2385 (62%) having ILD-related inhalational exposure. Exposed patients were younger, particularly in the idiopathic pulmonary fibrosis subgroup. Inhalational exposure was associated with male gender (adjusted OR 1.46, 95% CI 1.28-1.68, p < 0.001) and family history of pulmonary fibrosis (adjusted OR 1.73, 95% CI 1.40-2.15, p < 0.001). Patients with any inhalational exposure had improved transplant-free survival (hazard ratio 0.81, 95% CI 0.71-0.92, p = 0.001); this effect persisted across diagnostic subtypes. The relationship between exposures and annual change in forced vital capacity varied by ILD subtype. CONCLUSION: Patients with fibrotic ILD report high prevalence of inhalational exposures across ILD subtypes. These exposures were associated with younger age at diagnosis, male gender and family history of pulmonary fibrosis. Identification of an inhalational exposure was associated with a survival benefit. These findings suggest that inhaled exposures may impact clinical outcomes in patients with ILD, and future work should characterize the mechanisms underlying these relationships.

Blood Transcriptomics Predicts Progression of Pulmonary Fibrosis and Associated Natural Killer Cells.

Rationale: Disease activity in idiopathic pulmonary fibrosis (IPF) remains highly variable, poorly understood, and difficult to predict. Objectives: To identify a predictor using short-term longitudinal changes in gene expression that forecasts future FVC decline and to characterize involved pathways and cell types. Methods: Seventy-four patients from COMET (Correlating Outcomes with Biochemical Markers to Estimate Time-Progression in IPF) cohort were dichotomized as progressors (≥10% FVC decline) or stable. Blood gene-expression changes within individuals were calculated between baseline and 4 months and regressed with future FVC status, allowing determination of expression variations, sample size, and statistical power. Pathway analyses were conducted to predict downstream effects and identify new targets. An FVC predictor for progression was constructed in COMET and validated using independent cohorts. Peripheral blood mononuclear single-cell RNA-sequencing data from healthy control subjects were used as references to characterize cell type compositions from bulk peripheral blood mononuclear RNA-sequencing data that were associated with FVC decline. Measurements and Main Results: The longitudinal model reduced gene-expression variations within stable and progressor groups, resulting in increased statistical power when compared with a cross-sectional model. The FVC predictor for progression anticipated patients with future FVC decline with 78% sensitivity and 86% specificity across independent IPF cohorts. Pattern recognition receptor pathways and mTOR pathways were downregulated and upregulated, respectively. Cellular deconvolution using single-cell RNA-sequencing data identified natural killer cells as significantly correlated with progression. Conclusions: Serial transcriptomic change predicts future FVC decline. An analysis of cell types involved in the progressor signature supports the novel involvement of natural killer cells in IPF progression.

Hospitalizations in patients with idiopathic pulmonary fibrosis.

BACKGROUND: Hospitalizations are common among patients with idiopathic pulmonary fibrosis (IPF). We investigated the impact of hospitalizations on outcomes in patients with IPF. METHODS: The IPF-PRO Registry is an observational US registry that enrolled patients with IPF that was diagnosed or confirmed at the enrolling center in the previous 6 months. Associations between patient characteristics and hospitalization, and between hospitalization and mortality, were analyzed using Cox regression models. RESULTS: A total of 1002 patients with IPF were enrolled into the IPF-PRO Registry. Over a median follow-up time of 23.7 months (maximum: 67.0 months), 568 patients (56.7%) had at least one hospitalization. Of these patients, 319 (56.2%) had at least one respiratory-related hospitalization and 120 (21.1%) had at least one hospitalization with ventilatory support. Younger age (HR 0.68 [95% CI 0.55, 0.84] per 5-year increase for patients < 62 years), lower BMI (0.96 [0.93, 0.98] per 1-point increase), lower FVC % predicted (0.90 [0.83, 0.97] per 10% increase), oxygen use at rest (2.85 [2.18, 3.72]) and history of pulmonary hypertension (2.02 [1.37, 2.96]) at enrollment were associated with an increased risk of respiratory-related hospitalization during follow-up. In a multivariable model, there was an eightfold increase in the risk of mortality during hospitalization or within 90 days of discharge compared with outside of this period. The risk of mortality associated with a respiratory hospitalization or a hospitalization with ventilatory support was even greater. CONCLUSIONS: Data from the IPF-PRO Registry demonstrate that hospitalizations are common among patients with IPF. The risk of mortality during hospitalization or within 90 days of discharge was high, particularly among patients who were hospitalized for a respiratory cause or received ventilatory support. Trial registration ClinicalTrials.gov, NCT01915511. Registered 5 August 2013, https://clinicaltrials.gov/ct2/show/NCT01915511.

The other connective tissue disease-associated interstitial lung diseases: Sjogren's syndrome, mixed connective tissue disease, and systemic lupus erythematosus.

PURPOSE OF REVIEW: We review the clinical manifestations of three less common connective tissue disease (CTD)-associated interstitial lung diseases (ILDs): Sjogren's syndrome (SjS), mixed CTD (MCTD), and systemic lupus erythematosus (SLE). RECENT FINDINGS: SjS is classically associated with lymphocytic interstitial pneumonia and cystic lung disease, but the most common type of ILD in Sjogren's patients is nonspecific interstitial pneumonia. ILD is prevalent in MCTD and associated with worse survival. SLE-associated ILD, while rare, is more common in those with CTD overlap syndromes. Regardless of underlying cause, a subset of patients with fibrotic CTD-associated ILD develop a progressive course for which antifibrotic agents and lung transplantation should be considered. SUMMARY: An understanding of the characteristics of ILD in SjS, MCTD, and SLE is important for the pulmonary specialist. Future research should identify risk factors for progression and develop additional treatment modalities for both CTD-related autoimmune features and progressive ILD.

Vessel-related structures predict UIP pathology in those with a non-IPF pattern on CT.

OBJECTIVES: To determine if a quantitative imaging variable (vessel-related structures [VRS]) could identify subjects with a non-IPF diagnosis CT pattern who were highly likely to have UIP histologically. METHODS: Subjects with a multidisciplinary diagnosis of interstitial lung disease including surgical lung biopsy and chest CT within 1 year of each other were included in the study. Non-contrast CT scans were analyzed using the Computer-Aided Lung Informatics for Pathology Evaluation and Rating (CALIPER) program, which quantifies the amount of various abnormal CT patterns on chest CT. Quantitative data were analyzed relative to pathological diagnosis as well as the qualitative CT pattern. RESULTS: CALIPER-derived volumes of reticulation (p = 0.012), honeycombing (p = 0.017), and VRS (p < 0.001) were associated with a UIP pattern on pathology on univariate analysis but only VRS was associated with a UIP pathology on multivariable analysis (p = 0.013). Using a VRS cut-off of 173 cm3, the sensitivity and specificity for pathological UIP were similar to those for standard qualitative CT assessment (55.9% and 80.4% compared to 60.6% and 80.4%, respectively). VRS differentiated pathological UIP cases in those with a non-IPF diagnosis CT category (p < 0.001) but not in other qualitative CT patterns (typical UIP, probable UIP, and indeterminate for UIP). The rate of pathological UIP in those with VRS greater than 173 cm3 (84.2%) was nearly identical to those who had a qualitative CT pattern of probable UIP (88.9%). CONCLUSIONS: VRS may be an adjunct to CT in predicting pathology in patients with interstitial lung disease. KEY POINTS: • Volume of vessel-related structures (VRS) was associated with usual interstitial pneumonia (UIP) on pathology. • This differentiation arose from those with CT scans with a non-IPF diagnosis imaging pattern. • Higher VRS has similar diagnostic ramifications for UIP as probable UIP, transitively suggesting in patients with high VRS, pathology may be obviated.

Genome-Wide Association Study of Susceptibility to Idiopathic Pulmonary Fibrosis.

Rationale: Idiopathic pulmonary fibrosis (IPF) is a complex lung disease characterized by scarring of the lung that is believed to result from an atypical response to injury of the epithelium. Genome-wide association studies have reported signals of association implicating multiple pathways including host defense, telomere maintenance, signaling, and cell-cell adhesion.Objectives: To improve our understanding of factors that increase IPF susceptibility by identifying previously unreported genetic associations.Methods: We conducted genome-wide analyses across three independent studies and meta-analyzed these results to generate the largest genome-wide association study of IPF to date (2,668 IPF cases and 8,591 controls). We performed replication in two independent studies (1,456 IPF cases and 11,874 controls) and functional analyses (including statistical fine-mapping, investigations into gene expression, and testing for enrichment of IPF susceptibility signals in regulatory regions) to determine putatively causal genes. Polygenic risk scores were used to assess the collective effect of variants not reported as associated with IPF.Measurements and Main Results: We identified and replicated three new genome-wide significant (P < 5 × 10-8) signals of association with IPF susceptibility (associated with altered gene expression of KIF15, MAD1L1, and DEPTOR) and confirmed associations at 11 previously reported loci. Polygenic risk score analyses showed that the combined effect of many thousands of as yet unreported IPF susceptibility variants contribute to IPF susceptibility.Conclusions: The observation that decreased DEPTOR expression associates with increased susceptibility to IPF supports recent studies demonstrating the importance of mTOR signaling in lung fibrosis. New signals of association implicating KIF15 and MAD1L1 suggest a possible role of mitotic spindle-assembly genes in IPF susceptibility.