Characteristics of pulse oximetry and arterial blood gas in patients with fibrotic interstitial lung disease

BACKGROUND

Fibrotic interstitial lung disease (ILD) is frequently associated with abnormal oxygenation; however, little is known about the accuracy of oxygen saturation by pulse oximetry (SpO2) compared with arterial blood gas (ABG) saturation (SaO2), the factors that influence the partial pressure of carbon dioxide (PaCO2) and the impact of PaCO2 on outcomes in patients with fibrotic ILD.

STUDY DESIGN AND METHODS

Patients with fibrotic ILD enrolled in a large prospective registry with a room air ABG were included. Prespecified analyses included testing the correlation between SaO2 and SpO2, the difference between SaO2 and SpO2, the association of baseline characteristics with both the difference between SaO2 and SpO2 and the PaCO2, the association of baseline characteristics with acid-base category, and the association of PaCO2 and acid-base category with time to death or transplant.

RESULTS

A total of 532 patients with fibrotic ILD were included. Mean resting SaO2 was 92±4% and SpO2 was 95±3%. Mean PaCO2 was 38±6 mmHg, with 135 patients having PaCO2 <35 mmHg and 62 having PaCO2 >45 mmHg. Correlation between SaO2 and SpO2 was mild to moderate (r=0.39), with SpO2 on average 3.0% higher than SaO2. No baseline characteristics were associated with the difference in SaO2 and SpO2. Variables associated with either elevated or abnormal (elevated or low) PaCO2 included higher smoking pack-years and lower baseline forced vital capacity (FVC). Lower baseline lung function was associated with an increased risk of chronic respiratory acidosis. PaCO2 and acid-base status were not associated with time to death or transplant.

INTERPRETATION

SaO2 and SpO2 are weakly-to-moderately correlated in fibrotic ILD, with limited ability to accurately predict this difference. Abnormal PaCO2 was associated with baseline FVC but was not associated with outcomes.

Impact of surgical lung biopsy on lung function and survival in patients with idiopathic pulmonary fibrosis in a multi-centre registry cohort

BACKGROUND AND OBJECTIVE

Establishing an accurate and timely diagnosis of idiopathic pulmonary fibrosis (IPF) is essential for appropriate management and prognostication. In some cases, surgical lung biopsy (SLB) is performed but carries non-negligible risk. The objective of this retrospective study was to determine if SLB is associated with accelerated lung function decline in patients with IPF using the Canadian Registry for Pulmonary Fibrosis.

METHODS

Linear mixed models and Cox proportional hazards regression models were used to compare decline in forced vital capacity (FVC)%, diffusion capacity of the lung (DLCO%) and risk of death or lung transplantation between SLB and non-SLB patients. Adjustments were made for baseline age, sex, smoking history, antifibrotic use, and lung function. A similar analysis compared lung function changes 12 months pre- and post-SLB.

RESULTS

A total of 81 SLB patients and 468 non-SLB patients were included. In the SLB group, the post-biopsy annual FVC% decline was 2.0% (±0.8) in unadjusted, and 2.1% (±0.8) in adjusted models. There was no difference in FVC% decline, DLCO% decline, or time to death or lung transplantation between the two groups, in adjusted or unadjusted models (all p-values >0.07). In the pre-post SLB group, no differences were identified in FVC% decline in unadjusted or adjusted models (p = 0.07 for both).

CONCLUSION

No association between SLB and lung function decline or risk of death or lung transplantation was identified in this multi-centre study of patients with IPF.

Validation of a Dyspnea Visual Analogue Scale in Fibrotic Interstitial Lung Disease

RATIONALE

A visual analogue scale (VAS) is a simple and easily administered tool for measuring impact of disease; however, little is known about the use of a Dyspnea VAS in interstitial lung disease (ILD).

OBJECTIVE

To validate the use of a Dyspnea VAS in a large and heterogenous cohort of patients with fibrotic ILD, including its minimal clinically important difference (MCID), responsiveness to change, and prognostic significance.

METHODS

Patients with fibrotic ILD were identified from a large prospective registry. Validity of a 100mm Dyspnea VAS was assessed by testing its correlation in change score with other measures of ILD severity, including the University of California San Diego Shortness of Breath Questionnaire (UCSDSOBQ), King's Brief Interstitial Lung Disease quality of life questionnaire Breathlessness and Activities Domain (KBILD-B), European Quality of Life visual analogue scale (EQ-VAS), forced vital capacity (FVC), and diffusion capacity of the lung for carbon monoxide (DLCO). Responsiveness of the Dyspnea VAS was qualitatively confirmed based on there being an observable difference in the change in Dyspnea VAS across tertiles of change in anchor variables. The minimum clinically important difference (MCID) in Dyspnea VAS was calculated using both anchor (linear regression) and distribution (one-half standard deviation) approaches, with anchors including the above variables that had a correlation with Dyspnea VAS (|r|0.30). The association of Dyspnea VAS with time to death or transplant was determined.

RESULTS

The cohort included 826 patients with fibrotic ILD, including 127 patients with follow-up measurements at 6 months. Mean baseline Dyspnea VAS was 5324mm. Dyspnea VAS change scores were moderately correlated with UCSDSOBQ (|r|=0.55) and KBILD-B (|r|=0.44), and weakly correlated with EQ-VAS (|r|=0.19), FVC% (|r|=0.21) and DLCO% (|r|=0.05). MCID was 2.7 to 4.5 using the more reliable anchor-based methods and 12.0 based on distribution-based methods. Dyspnea VAS was associated with time to death or transplant in unadjusted models and after adjustment for age and sex (hazard ratio 1.16 and 1.15 respectively, p<0.05 for both).

CONCLUSION

This study provides support for the use of Dyspnea VAS in patients with fibrotic ILD, with an estimated anchor-based MCID of 5mm.

Characteristics and risk factors of interstitial pneumonia with autoimmune features

BACKGROUND

Interstitial pneumonia with autoimmune features (IPAF) has features of connective tissue disease-associated interstitial lung disease (CTD-ILD), but without meeting criteria for a specific CTD. We compared baseline characteristics, survival, and response to treatment of IPAF to both CTD-ILD and unclassifiable ILD.

METHODS

Measurements were extracted from a prospective registry. Baseline features and survival were compared in IPAF against both CTD-ILD and unclassifiable ILD. Linear trajectory of lung function decline (%-predicted forced vital capacity [FVC%] and diffusion capacity of the lung for carbon monoxide [DLCO%]) before and after initiation of mycophenolate or azathioprine were compared in IPAF against both CTD-ILD and unclassifiable ILD using linear mixed models.

RESULTS

Compared to CTD-ILD (n = 1240), patients with IPAF (n = 128) were older, more frequently male, and had greater smoking history. Compared to unclassifiable ILD (n = 665), patients with IPAF were younger, more frequently female, and had worse baseline lung function. IPAF had higher mortality compared to CTD-ILD and similar risk of mortality compared to unclassifiable ILD. Mycophenolate initiation was associated with stabilization of FVC% and DLCO% in all ILD subtypes except for FVC% in patients with IPAF, and azathioprine initiation with stabilization of FVC% and DLCO% in all ILD subtypes except for FVC% decline in IPAF and DLCO% decline in CTD-ILD.

CONCLUSION

Patients with IPAF had worse survival compared to those with CTD-ILD and similar mortality to unclassifiable ILD, with treatment being associated with stabilization in lung function in all three ILDs. It is uncertain whether IPAF should be considered a distinct ILD diagnostic subgroup.

Impact of Antigen Exposure on Outcomes and Treatment Response in Fibrotic Hypersensitivity Pneumonitis

BACKGROUND

Patients with fibrotic hypersensitivity pneumonitis (fHP) are frequently treated with immunosuppression to slow lung function decline; however, the impact of this treatment has not been studied across different types of antigen exposure.

RESEARCH QUESTION

In patients with fHP, do disease outcomes and response to treatment vary by antigen type?.

STUDY DESIGN AND METHODS

A multicenter interstitial lung disease database (Canadian Registry for Pulmonary Fibrosis) was used to identify patients with fHP. The causative antigen was categorized as avian, mold, unknown, or other. Treatment was defined as mycophenolate ≥ 1,000 mg/d or azathioprine ≥ 75 mg/d for ≥ 30 days. Statistical analysis included t tests, χ2 tests, and one-way analysis of variance. Unadjusted and adjusted competing risks and Cox proportional hazards models were used to assess survival.

RESULTS

A total of 344 patients were identified with the following causative antigens: avian (n = 93; 27%), mold (n = 88; 26%), other (n = 15; 4%), and unknown (n = 148; 43%). Patient characteristics and lung function were similar among antigen groups with a mean FVC % predicted of 75 ± 20. The percent of patients treated with immunosuppression was similar between antigens with 58% of patients treated. There was no change in lung function or symptom scores with the initiation of immunosuppression in the full cohort. Immunosuppression was not associated with a change in survival for patients with avian or mold antigen (avian: hazard ratio, 0.41; 95% CI, 0.11-1.59; P = .20; mold: hazard ratio, 1.13; 95% CI, 0.26-4.97; P = .88). For patients with unknown causative antigen, survival was worse when treated with immunosuppression (hazard ratio, 2.65; 95% CI, 1.01-6.92; P = .047).

INTERPRETATION

Response to immunosuppression varies by antigen type in patients with fHP. Additional studies are needed to test the role of immunosuppression in fHP, and particularly in those with an unknown antigen.

Predicting New-onset Exertional and Resting Hypoxemia in Fibrotic Interstitial Lung Disease

Rationale: Hypoxemia in fibrotic interstitial lung disease (ILD) indicates disease progression and is of prognostic significance. The onset of hypoxemia signifies disease progression and predicts mortality in fibrotic ILD. Accurately predicting new-onset exertional and resting hypoxemia prompts appropriate patient discussion and timely consideration of home oxygen. Objectives: We derived and externally validated a risk prediction tool for both new-onset exertional and new-onset resting hypoxemia. Methods: This study used ILD registries from Canada for the derivation cohort and from Australia and the United States for the validation cohort. New-onset exertional and resting hypoxemia were defined as nadir oxyhemoglobin saturation < 88% during 6-minute-walk tests, resting oxyhemoglobin saturation < 88%, or the initiation of ambulatory or continuous oxygen. Candidate predictors included patient demographics, ILD subtypes, and pulmonary function. Time-varying Cox regression was used to identify the top-performing prediction model according to Akaike information criterion and clinical usability. Model performance was assessed using Harrell's C-index and goodness-of-fit (GoF) likelihood ratio test. A categorized risk prediction tool was developed. Results: The best-performing prediction model for both new-onset exertional and new-onset resting hypoxemia included age, body mass index, a diagnosis of idiopathic pulmonary fibrosis, and percent predicted forced vital capacity and diffusing capacity of carbon monoxide. The risk prediction tool exhibited good performance for exertional hypoxemia (C-index, 0.70; GoF, P = 0.85) and resting hypoxemia (C-index, 0.77; GoF, P = 0.27) in the derivation cohort, with similar performance in the validation cohort except calibration for resting hypoxemia (GoF, P = 0.001). Conclusions: This clinically applicable risk prediction tool predicted new-onset exertional and resting hypoxemia at 6 months in the derivation cohort and a diverse validation cohort. Suboptimal GoF in the validation cohort likely reflected overestimation of hypoxemia risk and indicated that the model is not flawed because of underestimation of hypoxemia.

Transbronchial Lung Cryobiopsy and Surgical Lung Biopsy: A Prospective Multi-Centre Agreement Clinical Trial (CAN-ICE)

Rationale: Transbronchial cryobiopsy (TBCB) for the diagnosis of interstitial lung disease (ILD) has shown promising results, but prospective studies with matched surgical lung biopsy (SLB) have yielded conflicting results. Objectives: We aimed to assess within- and between-center diagnostic agreement between TBCB and SLB at both the histopathologic and multidisciplinary discussion (MDD) levels in patients with diffuse ILD. Methods: In a multicenter prospective study, we performed matched TBCB and SLB in patients referred for SLB. After a blinded review by three pulmonary pathologists, all cases were reviewed by three independent ILD teams in an MDD. MDD was performed first with TBCB, then with SLB in a second session. Within-center and between-center diagnostic agreement was evaluated using percentages and correlation coefficients. Measurements and Main Results: Twenty patients were recruited and underwent contemporaneous TBCB and SLB. Within-center diagnostic agreement between TBCB-MDD and SLB-MDD was reached in 37 of the 60 (61.7%) paired observations, resulting in a Cohen's κ value of 0.46 (95% confidence interval [CI], 0.29-0.63). Diagnostic agreement increased among high-confidence or definitive diagnoses on TBCB-MDD (21 of 29 [72.4%]), but not significantly, and was more likely among cases with SLB-MDD diagnoses of idiopathic pulmonary fibrosis than fibrotic hypersensitivity pneumonitis (13 of 16 [81.2%] vs. 16 of 31 [51.6%]; P = 0.047). Between-center agreement for cases was markedly higher for SLB-MDD (κ = 0.71 [95% CI, 0.52-0.89]) than TBCB-MDD (κ = 0.29 [95% CI, 0.09-0.49]). Conclusions: This study demonstrated moderate TBCB-MDD and SLB-MDD diagnostic agreement for ILD, while between-center agreement was fair for TBCB-MDD and substantial for SLB-MDD. Clinical trial registered with www.clinicaltrials.gov (NCT02235779).

Treatment of rheumatoid arthritis-associated interstitial lung disease in a multi-center registry cohort

Background

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is challenging to manage, with a paucity of robust data to guide treatment. Our aim was to characterize the pharmacologic treatment of RA-ILD utilizing a retrospective design in a national multi-center prospective cohort, and to identify associations between treatment and change in lung function and survival.

Methods

Patients with RA-ILD and a radiological pattern of non-specific interstitial pneumonia (NSIP) or usual interstitial pneumonia (UIP) were included. Unadjusted and adjusted linear mixed models and Cox proportional hazards models were used to compare lung function change and risk of death or lung transplant by radiologic patterns and treatment.

Results

Of 161 patients with RA-ILD, UIP pattern was more common than NSIP (55.9% vs. 44.1%). Only 44/161 (27%) patients were treated over median follow-up of 4 years with medication choice appearing unrelated to patient-specific variables. Decline in forced vital capacity (FVC) was not associated with treatment. Patients with NSIP had lower risk of death or transplant, compared to UIP (P=0.0042). In patients with NSIP, there was no difference in time to death or transplant comparing treated to untreated in adjusted models [hazard ratio (HR) =0.73; 95% confidence interval (CI): 0.15-3.62; P=0.70]. Similarly, in patients with UIP, there was no difference in time to death or lung transplant between treated and untreated in adjusted models (HR =1.06; 95% CI: 0.49-2.28; P=0.89).

Conclusions

Treatment of RA-ILD is heterogeneous, with most patients in this cohort not receiving treatment. Patients with UIP had worse outcomes compared to NSIP, similar to other cohorts. Randomized clinical trials are needed to inform pharmacologic therapy in this patient population.

Sex- and Race-Based Differences in the Treatment of Interstitial Lung Diseases in North America and Australasia

BACKGROUND

Biological sex, gender, and race are important considerations in patients with interstitial lung diseases (ILDs).

RESEARCH QUESTION

Does a patient's sex assigned at birth, and race, influence ILD treatment initiation?

STUDY DESIGN AND METHODS

Patients with ILD from three longitudinal prospective registries were compared in this observational study. ILD-related medications included antifibrotics and immunomodulating medications. Race was dichotomized as "White" vs "non-White." Time to treatment initiation was determined from the date of the initial ILD registry visit to the date of first medication initiation. Proportions of treated patients were compared between groups by χ2 test. Cox proportional analysis was used to determine how sex and race were associated with time to treatment initiation stratified by ILD diagnosis.

RESULTS

A total of 4,572 patients were included across all cohorts. The proportion of men who received treatment was higher than for women in the Canadian cohort (47% vs 40%; P < .001), and the proportion of White patients who received treatment was also higher compared with non-White patients (46% vs 36%; P < .001). In contrast, the proportion of treated men in the Chicago cohort was lower compared with women (56% vs 64%; P = .005), and that of White patients was lower compared with non-White patients (56% vs 69%; P < .001). No sex- or race-based differences in proportions of patients treated were found in the Australasian cohort. White race was significantly associated with earlier treatment initiation compared with non-White race across diagnoses in the Canadian cohort, whereas the opposite association was found in the Australasian cohort.

INTERPRETATION

Sex- and race-based differences exist in the initiation of ILD treatment, with variability across different cohorts in different countries. Reasons for these differences need to be further explored in future studies.

Skin disorders and interstitial lung disease: Part II-The spectrum of cutaneous diseases with lung disease association

Part 2 of this 2-part CME introduces dermatologists to noninfectious inflammatory skin diseases associated with pulmonary involvement. In many cases, dermatologists may be the first physicians recognizing respiratory complications associated with these diagnoses. Because pulmonary involvement is often the leading cause of morbidity and mortality, dermatologists should be comfortable screening and monitoring for lung disease in high-risk patients, recognizing cutaneous stigmata of lung disease in these patients and referring to pulmonary specialists, when appropriate, for prompt treatment initiation. Some treatments used for skin disease may not be appropriate in the context of lung disease and hence, choosing a holistic approach is important. Interstitial lung disease and pulmonary hypertension are the most common pulmonary complications and a significant cause of mortality in autoimmune connective tissue diseases, especially systemic sclerosis, dermatomyositis, and mixed connective tissue disease. Pulmonary complications, notably interstitial lung disease, are also common and life-threatening in sarcoidosis and vasculitis, while they are variable in neutrophilic and autoimmune blistering diseases.

Eligibility criteria from pharmaceutical randomised controlled trials of idiopathic pulmonary fibrosis: A registry-based study

BACKGROUND

Little is known about generalisability of randomised controlled trials (RCTs) for idiopathic pulmonary fibrosis (IPF). We evaluated eligibility criteria for phase III IPF RCTs to determine their representativeness in clinical registries, and calculated forced vital capacity (FVC) changes according to eligibility criteria.

METHODS

Common eligibility criteria used in >60% of IPF RCTs were identified from a literature search and applied to patients with IPF from prospective Australian and Canadian registries. Additional pre-specified criteria of 6-min walk distance (6 MWD) and different measures of preceding disease progression were also evaluated. Joint longitudinal-survival modelling was used to compare FVC decline according to eligibility for individual and composite criteria.

RESULTS

Of 990 patients with IPF, 527 (53%) met all common RCT eligibility criteria at the first clinic visit, including 343 with definite IPF and 184 with radiological probable usual interstitial pneumonia pattern without histological confirmation (i.e., provisional IPF). The percentages of eligible patients for landmark RCTs of nintedanib and pirfenidone were 19-50%. Adding 6 MWD ≥150 m and different measures of preceding disease progression to the composite common criteria reduced the percentages of patients meeting eligibility to 52% (n=516) and 4-18% (n=12-61), respectively. Patients meeting the composite common criteria had less rapid 1-year FVC decline than those who did not (-90 versus -103 ml, p=0.01). Definite IPF generally had more rapid 1-year FVC decline compared to provisional IPF.

CONCLUSIONS

Eligibility criteria of previous IPF RCTs have limited generalisability to clinical IPF populations, with FVC decline differing between eligible and ineligible populations.

Trajectories and Prognostic Significance of 6-Minute Walk Test Parameters in Fibrotic Interstitial Lung Disease: A Multicenter Study

BACKGROUND

Functional capacity, as measured by the 6-min walk test (6MWT), is often reduced in fibrotic interstitial lung disease (ILD). This study evaluated longitudinal changes and the prognostic significance of 6MWT parameters, and explored change in oxygenation status as a physiological criterion to define disease progression in patients with fibrotic ILD.

RESEARCH QUESTIONS

What are the trajectories and prognostic value of 6MWT parameters in patients with fibrotic ILD?

STUDY DESIGN AND METHODS

Using prospective registries in Australia and Canada, patients with idiopathic pulmonary fibrosis (IPF) and non-IPF fibrotic ILD were stratified by the presence of criteria for progressive pulmonary fibrosis (PPF). The cumulative incidence of exertional and resting hypoxemia and changes in 6-min walk distance (6MWD) and composite indices (distance-saturation product and distance-saturation-oxygen product) were determined, with prognostic significance evaluated at the time of meeting criteria for PPF. New-onset exertional or resting hypoxemia was evaluated as another potential criterion for PPF.

RESULTS

Patients with IPF/PPF (n = 126) and non-IPF/PPF (n = 227) had a similar cumulative incidence of exertional hypoxemia and annualized decline in 6MWD and composite indices, which varied across each PPF criterion. Patients with IPF/non-PPF (n = 231) and non-IPF/non-PPF (n = 531) had a significantly lower incidence of hypoxemia than those with IPF/PPF, with an annualized increase in 6MWD and composite indices in the non-IPF/non-PPF group. Exertional or resting hypoxemia at the time of meeting criteria for PPF was independently associated with reduced transplant-free survival in IPF and non-IPF, adjusting for patient demographics and lung function. Adding new-onset exertional or resting hypoxemia as a physiological criterion reduced the median time to development of PPF from 11.2 to 6.7 months in IPF and from 11.7 to 5.6 months in non-IPF in patients who eventually met both definitions (P < .001 for both).

INTERPRETATION

Patients with IPF/PPF and non-IPF/PPF have comparable deterioration in functional capacity. Oxygenation status provides prognostic information in PPF and may assist in defining disease progression in fibrotic ILD.

Mapping EQ5D utilities from forced vital capacity and diffusing capacity in fibrotic interstitial lung disease

OBJECTIVES

Fibrotic interstitial lung disease (ILD) includes a large group of conditions that lead to scarring of the lungs. The lack of available 5-level EuroQol 5D (EQ5D) data has limited the ability to conduct economic evaluations in ILD. The purpose of this study was to develop and validate a mapping algorithm that predicts EQ5D utilities from commonly collected pulmonary function measurements (forced vital capacity [FVC] and diffusing capacity of the lung for carbon monoxide [DLCO]) in fibrotic ILDs.

METHODS

EQ5D utility and pulmonary function measurements from the Canadian Registry for Pulmonary Fibrosis were included. Ordinary least squares (OLS), beta regression, two-part, and tobit models were used to map EQ5D utilities from FVC or DLCO. Model performance was assessed by comparing the predicted and observed utilities. Subgroup analyses were also conducted to test how well models performed across different patient characteristics. The models were then externally validated in the Australian Idiopathic Pulmonary Fibrosis Registry.

RESULTS

The OLS model performed as well as other more complex models (root mean squared error: 0.17 for FVC and 0.16 for DLCO). As with the other models, the OLS algorithm performed well across the different subgroups (except for EQ5D utilities < 0.5) and in the external validation cohort.

CONCLUSION

We developed a mapping algorithm that predicts EQ5D utilities from FVC and DLCO, with the intent that this algorithm can be applied to clinical trial populations and real-world cohorts that have not prioritized collection of health-related utilities. The mapping algorithm can be used in future economic evaluations of potential ILD therapies.

Machine learning in radiology: the new frontier in interstitial lung diseases

Challenges for the effective management of interstitial lung diseases (ILDs) include difficulties with the early detection of disease, accurate prognostication with baseline data, and accurate and precise response to therapy. The purpose of this Review is to describe the clinical and research gaps in the diagnosis and prognosis of ILD, and how machine learning can be applied to image biomarker research to close these gaps. Machine-learning algorithms can identify ILD in at-risk populations, predict the extent of lung fibrosis, correlate radiological abnormalities with lung function decline, and be used as endpoints in treatment trials, exemplifying how this technology can be used in care for people with ILD. Advances in image processing and analysis provide further opportunities to use machine learning that incorporates deep-learning-based image analysis and radiomics. Collaboration and consistency are required to develop optimal algorithms, and candidate radiological biomarkers should be validated against appropriate predictors of disease outcomes.

Association of Particulate Matter Exposure With Lung Function and Mortality Among Patients With Fibrotic Interstitial Lung Disease

Importance

Particulate matter 2.5 μm or less in diameter (PM2.5) is associated with adverse outcomes for patients with idiopathic pulmonary fibrosis, but its association with other fibrotic interstitial lung diseases (fILDs) and the association of PM2.5 composition with adverse outcomes remain unclear.

Objective

To investigate the association of PM2.5 exposure with mortality and lung function among patients with fILD.

Design, Setting, and Participants

In this multicenter, international, prospective cohort study, patients were enrolled in the Simmons Center for Interstitial Lung Disease Registry at the University of Pittsburgh in Pittsburgh, Pennsylvania; 42 sites of the Pulmonary Fibrosis Foundation Registry; and 8 sites of the Canadian Registry for Pulmonary Fibrosis. A total of 6683 patients with fILD were included (Simmons, 1424; Pulmonary Fibrosis Foundation, 1870; and Canadian Registry for Pulmonary Fibrosis, 3389). Data were analyzed from June 1, 2021, to August 2, 2022.

Exposures

Exposure to PM2.5 and its constituents was estimated with hybrid models, combining satellite-derived aerosol optical depth with chemical transport models and ground-based PM2.5 measurements.

Main Outcomes and Measures

Multivariable linear regression was used to test associations of exposures 5 years before enrollment with baseline forced vital capacity and diffusion capacity for carbon monoxide. Multivariable Cox models were used to test associations of exposure in the 5 years before censoring with mortality, and linear mixed models were used to test associations of exposure with a decrease in lung function. Multiconstituent analyses were performed with quantile-based g-computation. Cohort effect estimates were meta-analyzed. Models were adjusted for age, sex, smoking history, race, a socioeconomic variable, and site (only for Pulmonary Fibrosis Foundation and Canadian Registry for Pulmonary Fibrosis cohorts).

Results

Median follow-up across the 3 cohorts was 2.9 years (IQR, 1.5-4.5 years), with death for 28% of patients and lung transplant for 10% of patients. Of the 6683 patients in the cohort, 3653 were men (55%), 205 were Black (3.1%), and 5609 were White (84.0%). Median (IQR) age at enrollment across all cohorts was 66 (58-73) years. A PM2.5 exposure of 8 μg/m3 or more was associated with a hazard ratio for mortality of 4.40 (95% CI, 3.51-5.51) in the Simmons cohort, 1.71 (95% CI, 1.32-2.21) in the Pulmonary Fibrosis Foundation cohort, and 1.45 (95% CI, 1.18-1.79) in the Canadian Registry for Pulmonary Fibrosis cohort. Increasing exposure to sulfate, nitrate, and ammonium PM2.5 constituents was associated with increased mortality across all cohorts, and multiconstituent models demonstrated that these constituents tended to be associated with the most adverse outcomes with regard to mortality and baseline lung function. Meta-analyses revealed consistent associations of exposure to sulfate and ammonium with mortality and with the rate of decrease in forced vital capacity and diffusion capacity of carbon monoxide and an association of increasing levels of PM2.5 multiconstituent mixture with all outcomes.

Conclusions and Relevance

This cohort study found that exposure to PM2.5 was associated with baseline severity, disease progression, and mortality among patients with fILD and that sulfate, ammonium, and nitrate constituents were associated with the most harm, highlighting the need for reductions in human-derived sources of pollution.

Neighbourhood disadvantage impacts on pulmonary function in patients with sarcoidosis

Background

This multicentre, international, prospective cohort study evaluated whether patients with pulmonary sarcoidosis living in neighbourhoods with greater material and social disadvantage experience worse clinical outcomes.

Methods

The area deprivation index and the Canadian Index of Multiple Deprivation evaluate neighbourhood-level disadvantage in the US and Canada, with higher scores reflecting greater disadvantage. Multivariable linear regression evaluated associations of disadvantage with baseline forced vital capacity (FVC) or diffusing capacity of the lung for carbon monoxide (D_LCO) and linear mixed effects models for associations with rate of FVC or D_LCO decline, and competing hazards models were used for survival analyses in the US cohort, evaluating competing outcomes of death or lung transplantation. Adjustments were made for age at diagnosis, sex, race and smoking history.

Results

We included 477 US and 122 Canadian patients with sarcoidosis. Higher disadvantage was not associated with survival or baseline FVC. The highest disadvantage quartile was associated with lower baseline D_LCO in the US cohort (β = −6.80, 95% CI −13.16 to −0.44, p=0.04), with similar findings in the Canadian cohort (β = −7.47, 95% CI −20.28 to 5.33, p=0.25); with more rapid decline in FVC and D_LCO in the US cohort (FVC β = −0.40, 95% CI −0.70 to −0.11, p=0.007; D_LCO β = −0.59, 95% CI −0.95 to −0.23, p=0.001); and with more rapid FVC decline in the Canadian cohort (FVC β = −0.80, 95% CI −1.37 to −0.24, p=0.003).

Conclusion

Patients with sarcoidosis living in high disadvantage neighbourhoods experience worse baseline lung function and more rapid lung function decline, highlighting the need for better understanding of how neighbourhood-level factors impact individual patient outcomes.

Greater neighbourhood disadvantage is associated with worse baseline lung function and more rapid lung function decline in patients with sarcoidosis in both US and Canadian cohorts, highlighting the impact of socioeconomic disparities in this populationhttps://bit.ly/3R8gUuc

Prevalence and characteristics of progressive fibrosing interstitial lung disease in a prospective registry

BACKGROUND

Progressive fibrosing interstitial lung disease (PF-ILD) is characterised by progressive physiological, symptomatic and/or radiographic worsening. The real-world prevalence and characteristics of PF-ILD remain uncertain.

METHODS

Patients were enrolled from the Canadian Registry for Pulmonary Fibrosis between 2015 and 2020. PF-ILD was defined as a relative forced vital capacity (FVC) decline ≥10%, death, lung transplantation or any two of: relative FVC decline ≥5% and <10%, worsening respiratory symptoms or worsening fibrosis on computed tomography of the chest, all within 24 months of diagnosis. Time-to-event analysis compared progression between key diagnostic subgroups. Characteristics associated with progression were determined by multivariable regression.

RESULTS

Of 2746 patients with fibrotic ILD (mean±sd age 65±12 years; 51% female), 1376 (50%) met PF-ILD criteria in the first 24 months of follow-up. PF-ILD occurred in 427 (59%) patients with idiopathic pulmonary fibrosis (IPF), 125 (58%) with fibrotic hypersensitivity pneumonitis (HP), 281 (51%) with unclassifiable ILD (U-ILD) and 402 (45%) with connective tissue disease-associated ILD (CTD-ILD). Compared with IPF, time to progression was similar in patients with HP (hazard ratio (HR) 0.96, 95% CI 0.79-1.17), but was delayed in patients with U-ILD (HR 0.82, 95% CI 0.71-0.96) and CTD-ILD (HR 0.65, 95% CI 0.56-0.74). Background treatment varied across diagnostic subtypes, with 66% of IPF patients receiving antifibrotic therapy, while immunomodulatory therapy was utilised in 49%, 61% and 37% of patients with CHP, CTD-ILD and U-ILD, respectively. Increasing age, male sex, gastro-oesophageal reflux disease and lower baseline pulmonary function were independently associated with progression.

CONCLUSIONS

Progression is common in patients with fibrotic ILD, and is similarly prevalent in HP and IPF. Routinely collected variables help identify patients at risk for progression and may guide therapeutic strategies.

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.

Clinical relevance of rheumatoid factor and anti-citrullinated peptides in fibrotic interstitial lung disease

BACKGROUND AND OBJECTIVE

Rheumatoid arthritis (RA) is a frequent cause of interstitial lung disease (ILD); however, the impact of rheumatoid factor and anti-citrullinated peptide antibody seropositivity in ILD without connective tissue disease (CTD) is unclear. We examined the association of seropositivity with ILD progression, mortality and response to immunosuppression in non-CTD ILD.

METHODS

A total of 1570 non-CTD patients (with idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, interstitial pneumonia with autoimmune features or unclassifiable ILD) and 181 RA-ILD patients were included from a prospective registry. Longitudinal forced vital capacity (FVC), transplant-free survival and incidence of progressive fibrosing-ILD (PF-ILD) were compared between seronegative non-CTD ILD (reference group), seropositive non-CTD ILD and RA-ILD using linear mixed-effect and Cox proportional hazards models adjusted for age, sex, smoking pack-years and baseline FVC. Interaction between seropositivity and immunosuppression on FVC decline was assessed in patients with ≥6 months of follow-up before and after the treatment.

RESULTS

Two hundred and seventeen (13.8%) patients with seropositive non-CTD ILD had similar rates of FVC decline and transplant-free survival compared to seronegative non-CTD ILD, but more frequently met the criteria for PF-ILD (hazard ratio [HR] = 1.35, p = 0.004). RA-ILD had slower FVC decline (p = 0.03), less PF-ILD (HR = 0.75, p = 0.03) and lower likelihood of lung transplant or death (HR = 0.66, p = 0.01) compared to seronegative non-CTD ILD. No interaction was found between seropositivity and treatment on FVC decline in non-CTD ILD.

CONCLUSION

Seropositivity in non-CTD ILD was not associated with improved outcomes or treatment response, highlighting the importance of other disease features in determining prognosis and predicting response to immunosuppression.

Association of BMI with pulmonary function, functional capacity, symptoms, and quality of life in ILD

Obesity is a health epidemic associated with greater morbidity and mortality in the general population. Mass loading of the thorax from obesity leads to a restrictive pulmonary defect that reduces lung capacity in obese individuals without pulmonary disease, and may exacerbate the restrictive pulmonary physiology that is characteristic of interstitial lung disease (ILD). The purpose of this study was to test the association of body mass index (BMI) with pulmonary function, functional capacity, and patient-reported outcomes (dyspnea and quality of life) in patients with ILD. We analyzed 3169 patients with fibrotic ILD from the Canadian Registry for Pulmonary Fibrosis. Patients were subcategorized as underweight (BMI<18.5 kg/m2), normal weight (18.5≤BMI<25), overweight (25≤BMI<30), obese I (30≤BMI<35), obese II (35≤BMI<40), and obese III (BMI>40). Analysis was performed using a linear regression with adjustment for common prognostic variables. Overweight and obese BMI categories were associated with worse pulmonary function, functional capacity, dyspnea, and quality of life compared to normal weight. This is likely a result of mass loading on the thorax, and we speculate that intentional weight-loss may improve lung function and functional capacity in obese patients with fibrotic ILD. The underweight BMI category was also associated with worse functional capacity compared to normal weight, which may reflect greater disease severity or the presence of other comorbidities. Future work should explore the clinical utility of BMI to improve patient outcomes.

Sex and gender in interstitial lung diseases

Sex and gender differences influence key domains of research, lung health, healthcare access and healthcare delivery. In interstitial lung diseases (ILDs), mouse models of pulmonary fibrosis are clearly influenced by sex hormones. Additionally, short telomeres, a biomarker of telomere regulation gene mutations, are impacted by sex, while heritability unexplained by genetic variation may be attributable to gendered environmental factors that drive epigenetic control. Diseases like idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, occupational ILDs, connective tissue-associated ILDs and lymphangioleiomyomatosis have different prevalence and prognosis between men and women. These differences arise from a complex interplay between biological sex and sociocultural gender influencing genetics, epigenomic modifiers, hormones, immune function, response to treatment and interaction with healthcare systems. Much work remains to be done to systematically integrate sex and gender analysis into relevant domains of science and clinical care in ILD, from strategic considerations for establishing research priorities to guidelines for establishing best clinical practices. Accounting for sex and gender in ILD is essential to the practice of individualised, patient-centred medicine.

Effect of continued antifibrotic therapy after forced vital capacity decline in patients with idiopathic pulmonary fibrosis; a real world multicenter cohort study

RATIONALE

Longitudinal data on the impact of continued, switched or discontinued antifibrotic therapy in patients with idiopathic pulmonary fibrosis (IPF) who have disease progression is needed.

OBJECTIVE

We hypothesized that ongoing antifibrotic use (versus discontinuation) in the setting of forced vital capacity (FVC) decline would be associated with less future decline and lower likelihood of a composite outcome of FVC decline, lung transplant, or death.

METHODS

We performed a multicenter cohort study using data from the Canadian Registry for Pulmonary Fibrosis in patients with IPF with FVC decline ≥10% over 6 months on antifibrotic therapy. The association of continued, switched or discontinued therapy with (1) further change in FVC and (2) a composite of FVC decline ≥10%, transplant, or death, in the subsequent 6 months, was assessed using adjusted linear and logistic regression modelling, respectively. Generalized estimating equations accounted for repeated observations per patient.

RESULTS

165 patients had a decline in FVC ≥10% over 6 months while receiving antifibrotic therapy. Compared to continued use, antifibrotic discontinuation after FVC decline was associated with greater additional FVC decline (-207 mL 95%CI -353 to -62, p = 0.005) and higher odds of FVC decline ≥10%, transplant, or death (odds ratio 12.2 95%CI 1.2 to 130.5, p = 0.04). There was no difference between continued versus switched antifibrotic therapy.

CONCLUSIONS

Ongoing antifibrotic therapy in the setting of FVC decline is associated with less future FVC decline and lower odds of FVC decline ≥10%, transplant, or death in a real-world cohort of IPF.

Neighborhood-level Disadvantage Impacts on Patients with Fibrotic Interstitial Lung Disease

RATIONALE

Fibrotic interstitial lung diseases (fILDs) represent a group of pathologic entities characterized by scarring of the lungs and high morbidity and mortality. Research investigating how socioeconomic and residential factors impact outcomes in patients with fILDs is lacking.

OBJECTIVES

To determine the association between neighborhood-level disadvantage and presentation severity, disease progression, lung transplant, and mortality in patients with fILD from the United States (U.S.) and Canada.

METHODS

Multi-center, international, prospective cohort study of 4729 patients with fILD from one U.S. and eight Canadian ILD registry sites. Neighborhood-level disadvantage was measured by the area deprivation index (ADI) in the U.S. and the Canadian Index of Multiple Deprivation (CIMD) in Canada.

MEASUREMENTS AND MAIN RESULTS

In the U.S., but not Canadian cohort, patients with fILD living in neighborhoods with the greatest disadvantage (top quartile) experience the highest risk of mortality (hazard ratio=1.51, p=0.002) and in subgroups of patients with idiopathic pulmonary fibrosis (IPF), the top quartile of disadvantage experienced the lowest odds of lung transplant (odds ratio=0.46, p=0.04). Greater disadvantage was associated with reduced baseline diffusion capacity for carbon monoxide (DLCO) in both cohorts, but it was not associated with baseline forced vital capacity (FVC) or FVC or DLCO decline in either cohort.

CONCLUSIONS

Patients with fILD who live in areas with greater neighborhood-level disadvantage in the U.S. experience higher mortality, and patients with IPF experience lower odds of lung transplant. These disparities are not seen in Canadian patients, which may indicate differences in access to care between the U.S. and Canada.

Survival after inpatient or outpatient pulmonary rehabilitation in patients with fibrotic interstitial lung disease: a multicentre retrospective cohort study

BACKGROUND

The impact of pulmonary rehabilitation (PR) on survival in patients with fibrotic interstitial lung disease (ILD) is unknown. Given the challenges conducting a large randomised controlled trial, we aimed to determine whether improvement in 6-minute walk distance (6MWD) was associated with better survival.

METHODS

This retrospective, international cohort study included patients with fibrotic ILD participating in either inpatient or outpatient PR at 12 sites in 5 countries. Multivariable models were used to estimate the association between change in 6MWD and time to death or lung transplantation accounting for clustering by centre and other confounders.

RESULTS

701 participants (445 men and 256 women) with fibrotic ILD were included. The mean±SD ages of the 196 inpatients and 505 outpatients were 70±11 and 69±12 years, respectively. Baseline/changes in 6MWD were 262±128/55±83 m for inpatients and 358±125/34±65 m for outpatients. Improvement in 6MWD during PR was associated with lower hazard rates for death or lung transplant on adjusted analysis for both inpatient (HR per 10 m 0.94, 95% CI 0.91 to 0.97, p<0.001) and outpatient PR (HR 0.97, 95% CI 0.95 to 1.00, p=0.042). Participation in ≥80% of planned outpatient PR sessions was associated with a 33% lower risk of death (95% CI 0.49% to 0.92%).

CONCLUSIONS

Patients with fibrotic ILD who improved physical performance during PR had better survival compared with those who did not improve performance. Confirmation of these hypothesis-generating findings in a randomised controlled trial would be required to definitely change clinical practice, and would further support efforts to improve availability of PR for patients with fibrotic ILD.

Validation and minimum important difference of the UCSD Shortness of Breath Questionnaire in fibrotic interstitial lung disease

RATIONALE

The University of California, San Diego Shortness of Breath Questionnaire (UCSDSOBQ) is a frequently used domain-specific dyspnea questionnaire; however, there is little information available regarding its use and minimum important difference (MID) in fibrotic interstitial lung disease (ILD). We aimed to describe the key performance characteristics of the UCSDSOBQ in this population.

METHODS

UCSDSOBQ scores and selected anchors were measured in 1933 patients from the prospective multi-center Canadian Registry for Pulmonary Fibrosis. Anchors included the St. George's Respiratory Questionnaire (SGRQ), European Quality of Life 5 Dimensions 5 Levels questionnaire (EQ-5D-5L) and EQ visual analogue scale (EQ-VAS), percent-predicted forced vital capacity (FVC%), diffusing capacity of the lung for carbon monoxide (DLCO%), and 6-min walk distance (6MWD). Concurrent validity, internal consistency, ceiling and floor effects, and responsiveness were assessed, followed by estimation of the MID by anchor-based (linear regression) and distribution-based methods (standard error of measurement).

RESULTS

The UCSDSOBQ had a high level of internal consistency (Cronbach's alpha = 0.97), no obvious floor or ceiling effect, strong correlations with SGRQ, EQ-5D-5L, and EQ-VAS (|r| > 0.5), and moderate correlations with FVC%, DLCO%, and 6MWD (0.3 < |r| < 0.5). The MID estimate for UCSDSOBQ was 5 points (1-8) for the anchor-based method, and 4.5 points for the distribution-based method.

CONCLUSION

This study demonstrates the validity of UCSDSOBQ in a large and heterogeneous population of patients with fibrotic ILD, and provides a robust MID estimate of 5-8 points.

Genetically increased circulating FUT3 level leads to reduced risk of Idiopathic Pulmonary Fibrosis: a Mendelian Randomisation Study

Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal fibrotic interstitial lung disease. Few circulating biomarkers have been identified to have causal effects on IPF.To identify candidate IPF-influencing circulating proteins, we undertook an efficient screen of circulating proteins by applying a two-sample Mendelian randomisation (MR) approach with existing publicly available data. For instruments we used genetic determinants of circulating proteins which reside cis to the encoded gene (cis-SNPs), identified by two genome-wide association studies (GWASs) in European individuals (3301 and 3200 subjects). We then applied MR methods to test if the levels of these circulating proteins influenced IPF susceptibility in the largest IPF GWAS (2668 cases and 8591 controls). We validated the MR results using colocalization analyses to ensure that both the circulating proteins and IPF shared a common genetic signal.MR analyses of 834 proteins found that a one sd increase in circulating FUT3 and FUT5 was associated with a reduced risk of IPF (OR: 0.81, 95%CI: 0.74-0.88, p=6.3×10^-7, and OR: 0.76, 95%CI: 0.68-0.86, p=1.1×10^-5). Sensitivity analyses including multiple-cis SNPs provided similar estimates both for FUT3 (inverse variance weighted [IVW] OR: 0.84, 95%CI: 0.78-0.91, p=9.8×10^-6, MR-Egger OR: 0.69, 95%CI: 0.50-0.97, p=0.03) and FUT5 (IVW OR: 0.84, 95%CI: 0.77-0.92, p=1.4×10^-4, MR-Egger OR: 0.59, 95%CI: 0.38-0.90, p=0.01) FUT3 and FUT5 signals colocalized with IPF signals, with posterior probabilities of a shared genetic signal of 99.9% and 97.7%. Further transcriptomic investigations supported the protective effects of FUT3 for IPF.An efficient MR scan of 834 circulating proteins provided evidence that genetically increased circulating FUT3 level is associated with reduced risk of IPF.

A cluster-based analysis evaluating the impact of comorbidities in fibrotic interstitial lung disease

Background

Comorbidities are frequent and have been associated with poor quality of life, increased hospitalizations, and mortality in patients with interstitial lung disease (ILD). However, it is unclear how comorbidities lead to these negative outcomes and whether they could influence ILD disease progression. The goal of this study was to identify clusters of patients based on similar comorbidity profiles and to determine whether these clusters were associated with rate of lung function decline and/or mortality.

Methods

Patients with a major fibrotic ILD (idiopathic pulmonary fibrosis (IPF), fibrotic hypersensitivity pneumonitis, connective tissue disease-associated ILD, and unclassifiable ILD) from the CAnadian REgistry for Pulmonary Fibrosis (CARE-PF) were included. Hierarchical agglomerative clustering of comorbidities, age, sex, and smoking pack-years was conducted for each ILD subtype to identify combinations of these features that frequently occurred together in patients. The association between clusters and change in lung function over time was determined using linear mixed effects modeling, with adjustment for age, sex, and smoking pack-years. Kaplan Meier curves were used to assess differences in survival between the clusters.

Results

Discrete clusters were identified within each fibrotic ILD. In IPF, males with obstructive sleep apnea (OSA) had more rapid decline in FVC %-predicted (− 11.9% per year [95% CI − 15.3, − 8.5]) compared to females without any comorbidities (− 8.1% per year [95% CI − 13.6, − 2.7]; p = 0.03). Females without comorbidities also had significantly longer survival compared to all other IPF clusters. There were no significant differences in rate of lung function decline or survival between clusters in the other fibrotic ILD subtypes.

Conclusions

The combination of male sex and OSA may portend worse outcomes in IPF. Further research is required to elucidate the interplay between sex and comorbidities in ILD, as well as the role of OSA in ILD disease progression.

Minimum important difference of the EQ-5D-5L and EQ-VAS in fibrotic interstitial lung disease

RATIONALE

The European Quality of Life 5-Dimensions 5-Levels questionnaire (EQ-5D-5L) is a multidimensional patient-reported questionnaire that supports calculation of quality-adjusted life-years. Our objectives were to demonstrate feasibility of use and to calculate the minimum important difference (MID) of the EQ-5D-5L and its associated visual analogue scale (EQ-VAS) in patients with fibrotic interstitial lung disease (ILD).

METHODS

Patients who completed the EQ-5D-5L were identified from the prospective multicentre CAnadian REgistry for Pulmonary Fibrosis. Validity, internal consistency and responsiveness of the EQ-5D-5L were assessed, followed by calculation of the MID for the EQ-5D-5L and EQ-VAS. Anchor-based methods used an unadjusted linear regression against pulmonary function tests (PFTs) and dyspnoea and other quality of life questionnaires. Distribution-based method used one-half SD and SE measurement (SEM) calculations.

RESULTS

1816 patients were analysed, including 472 (26%) with idiopathic pulmonary fibrosis. EQ-5D-5L scores were strongly correlated with the dyspnoea and other quality of life questionnaires and weakly associated with PFTs. The estimated MID for EQ-5D-5L ranged from 0.0050 to 0.054 and from 0.078 to 0.095 for the anchor-based and distribution-based methods, respectively. The MID for EQ-VAS ranged from 0.5 to 5.0 and from 8.0 to 9.7 for the anchor-based and distribution-based methods. Findings were similar across ILD subtypes, sex and age.

CONCLUSION

We used a large and diverse cohort of patients with a variety of fibrotic ILD subtypes to suggest validity and MID of both the EQ-5D-5L and EQ-VAS. These findings will assist in designing future clinical trials and supporting cost-effectiveness analyses of potential treatments for patients with fibrotic ILD.

Effectiveness of Proton Pump Inhibitors in Idiopathic Pulmonary Fibrosis: A Population-Based Cohort Study

BACKGROUND

Gastroesophageal reflux disease is a common comorbidity in idiopathic pulmonary fibrosis (IPF) and may contribute to its progression. Anti-acid therapy, such as proton pump inhibitors (PPIs), has been considered as a potential treatment option for IPF. The evidence for this treatment comes from several observational studies affected by time-related bias.

RESEARCH QUESTION

Is use of PPIs in patients with IPF associated with a reduction in all-cause mortality, respiratory-related mortality, and respiratory-related hospitalization?

STUDY DESIGN AND METHODS

We used the UK Clinical Practice Research Datalink to identify a cohort of patients diagnosed with IPF between 2003 and 2016. The prevalent new-user cohort design was used to match patients initiating PPIs with non-users using time-conditional propensity scores, with follow-up until death or end of observation. Cox models were used to estimate hazard ratios (HR) and 95% CIs of death and of a respiratory-related hospitalization, correcting for informative censoring by inverse probability weighting.

RESULTS

There were 1,852 PPI users who were matched to 1,852 non-users identified among the cohort of patients with IPF, with a median survival of 2.8 years (mortality rate, 26.7 per 100 per year). The HR of all-cause mortality with PPI use was 1.07 (95% CI, 0.94-1.22), relative to non-use. For respiratory-related mortality, the HR was 1.10 (95% CI, 0.94-1.28) and 1.00 (95% CI, 0.86-1.16) for respiratory-related hospitalizations.

INTERPRETATION

PPI use was not associated with lower mortality or hospitalization incidence in this large study conducted among patients with IPF within a real-world setting of clinical practice and designed to avoid the time-related biases affecting previous studies. PPIs may not be as beneficial in treating IPF as suggested by some studies and conditionally recommended in treatment guidelines.

Patient gender bias on the diagnosis of idiopathic pulmonary fibrosis

Background

Patient sex has clinical and prognostic implications in idiopathic pulmonary fibrosis (IPF). It is not known if sex-related and gender-related discrepancies exist when establishing a diagnosis of IPF. The aim was to determine how patient gender influences the diagnosis of IPF and the physician’s diagnostic confidence.

Methods

This study was performed using clinical cases compiled from a single centre, then scored by respiratory physicians for a prior study. Using clinical information, physicians were asked to provide up to five diagnoses, together with their diagnostic confidence. Logistic regression was used to assess the odds of receiving a diagnosis of IPF based on patient gender. Prognostic discrimination between IPF and non-IPF was used to assess diagnostic accuracy with Cox proportional hazards modelling.

Results

Sixty cases were scored by 404 physicians. IPF was diagnosed more frequently in men compared with women (37.8% vs 10.6%; p<0.0001), and with greater mean diagnostic confidence (p<0.001). The odds of a male patient receiving an IPF diagnosis was greater than that of female patients, after adjusting for confounders (OR=3.05, 95% CI: 2.81 to 3.31), especially if the scan was not definite for the usual interstitial pneumonia pattern. Mortality was higher in women (HR=2.21, 95% CI: 2.02 to 2.41) than in men with an IPF diagnosis (HR=1.26, 95% CI: 1.20 to 1.33), suggesting that men were more often misclassified as having IPF.

Conclusion

Patient gender influences diagnosis of IPF: women may be underdiagnosed and men overdiagnosed with IPF.

MUC5B Promoter Variant and Rheumatoid Arthritis with Interstitial Lung Disease

BACKGROUND

Given the phenotypic similarities between rheumatoid arthritis (RA)-associated interstitial lung disease (ILD) (hereafter, RA-ILD) and idiopathic pulmonary fibrosis, we hypothesized that the strongest risk factor for the development of idiopathic pulmonary fibrosis, the gain-of-function MUC5B promoter variant rs35705950, would also contribute to the risk of ILD among patients with RA.

METHODS

Using a discovery population and multiple validation populations, we tested the association of the MUC5B promoter variant rs35705950 in 620 patients with RA-ILD, 614 patients with RA without ILD, and 5448 unaffected controls.

RESULTS

Analysis of the discovery population revealed an association of the minor allele of the MUC5B promoter variant with RA-ILD when patients with RA-ILD were compared with unaffected controls (adjusted odds ratio, 3.8; 95% confidence interval [CI], 2.8 to 5.2; P=9.7×10^-17). The MUC5B promoter variant was also significantly overrepresented among patients with RA-ILD, as compared with unaffected controls, in an analysis of the multiethnic case series (adjusted odds ratio, 5.5; 95% CI, 4.2 to 7.3; P=4.7×10^-35) and in a combined analysis of the discovery population and the multiethnic case series (adjusted odds ratio, 4.7; 95% CI, 3.9 to 5.8; P=1.3×10^-49). In addition, the MUC5B promoter variant was associated with an increased risk of ILD among patients with RA (adjusted odds ratio in combined analysis, 3.1; 95% CI, 1.8 to 5.4; P=7.4×10^-5), particularly among those with evidence of usual interstitial pneumonia on high-resolution computed tomography (adjusted odds ratio in combined analysis, 6.1; 95% CI, 2.9 to 13.1; P=2.5×10^-6). However, no significant association with the MUC5B promoter variant was observed for the diagnosis of RA alone.

CONCLUSIONS

We found that the MUC5B promoter variant was associated with RA-ILD and more specifically associated with evidence of usual interstitial pneumonia on imaging. (Funded by Société Française de Rhumatologie and others.).

A diagnostic model for chronic hypersensitivity pneumonitis

The objective of this study was to develop a diagnostic model that allows for a highly specific diagnosis of chronic hypersensitivity pneumonitis using clinical and radiological variables alone. Chronic hypersensitivity pneumonitis and other interstitial lung disease cases were retrospectively identified from a longitudinal database. High-resolution CT scans were blindly scored for radiographic features (eg, ground-glass opacity, mosaic perfusion) as well as the radiologist's diagnostic impression. Candidate models were developed then evaluated using clinical and radiographic variables and assessed by the cross-validated C-statistic. Forty-four chronic hypersensitivity pneumonitis and eighty other interstitial lung disease cases were identified. Two models were selected based on their statistical performance, clinical applicability and face validity. Key model variables included age, down feather and/or bird exposure, radiographic presence of ground-glass opacity and mosaic perfusion and moderate or high confidence in the radiographic impression of chronic hypersensitivity pneumonitis. Models were internally validated with good performance, and cut-off values were established that resulted in high specificity for a diagnosis of chronic hypersensitivity pneumonitis.

The effect of bronchodilators on forced vital capacity measurement in patients with idiopathic pulmonary fibrosis

BACKGROUND

Forced vital capacity (FVC) is a key measure of disease severity in patients with idiopathic pulmonary fibrosis (IPF) and is an important clinical trial endpoint. We hypothesize that reversible airflow limitation co-exists in a subgroup of patients with IPF, and that bronchodilator use will improve the performance characteristics of FVC.

METHODS

IPF patients with pre and post-bronchodilator spirometry testing performed were identified from two tertiary referral cohorts. The difference between pre and post-bronchodilator FVC (intra-test difference) was calculated. The test characteristics of pre and post-bronchodilator FVC change over time (inter-test difference) were assessed in patients with sequential spirometry, and were used to generate sample size estimates for hypothetical clinical trials using change in FVC as the primary endpoint.

RESULTS

There were 551 patients, contributing 967 unique spirometry tests. The mean intra-test increase in FVC with bronchodilator use was 0.04 L (2.71 vs. 2.75 L, p < 0.001). Reversible airflow limitation (increase in FEV1 or FVC of ≥12% and ≥200 mL) occurred in 9.1% of patients. The inter-test difference in change in FVC over time were equivalent for pre and post-bronchodilator (p = 0.65), leading to similar sample size estimates in a hypothetical clinical trial using change in FVC as the primary endpoint.

CONCLUSION

Approximately one in ten patients with IPF has physiological evidence of reversible airflow limitation, and bronchodilator use in these patients may improve the assessment of disease progression based on FVC change over time. Bronchodilator use does not appear to meaningfully impact the precision of FVC as an endpoint in clinical trials.

Predictors of mortality and progression in scleroderma-associated interstitial lung disease: a systematic review

BACKGROUND

Interstitial lung disease (ILD) is the leading cause of morbidity and mortality in patients with systemic sclerosis (SSc); however, prognostication of SSc-associated ILD (SSc-ILD) remains challenging. We conducted a systematic review to identify variables that predict mortality and ILD progression in SSc-ILD.

METHODS

Three databases were searched to identify all studies relating to predictors of mortality or ILD progression in SSc-ILD. Studies were eligible if they were published in English and included ≥ 10 adults with SSc-ILD. Two authors independently reviewed and extracted data from acceptable studies.

RESULTS

The initial search identified 3,145 unique citations. Twenty-seven studies, including six abstracts, met the inclusion criteria. A total of 1,616 patients with SSc-ILD were included. Patient-specific, ILD-specific, and SSc-specific variables predicted mortality and progression; however, most predictors were identified in only one study. Most studies did not fully account for potential confounders, and none of the studies included a validation cohort. Older age, lower FVC, and lower diffusing capacity of carbon monoxide predicted mortality in more than one study. Male sex, extent of disease on high-resolution CT (HRCT) scan, presence of honeycombing, elevated KL-6 values, and increased alveolar epithelial permeability were identified as predictors of both mortality and ILD progression on unadjusted analysis. The extent of disease on HRCT scan was the only variable that independently predicted both mortality and ILD progression.

CONCLUSIONS

Mortality and ILD progression were predicted by several patient-specific, ILD-specific, and SSc-specific factors. Additional prospective studies are required to validate these preliminary findings and to identify combinations of variables that accurately predict the prognosis of SSc-ILD.

Rheumatoid arthritis associated interstitial lung disease: a review

Rheumatoid arthritis is a common inflammatory disease affecting about 1% of the population. Interstitial lung disease is a serious and frequent complication of rheumatoid arthritis. Rheumatoid arthritis associated interstitial lung disease (RA-ILD) is characterized by several histopathologic subtypes. This article reviews the proposed pathogenesis and risk factors for RA-ILD. We also outline the important steps involved in the work-up of RA-ILD and review the evidence for treatment and prognosis.

Predictors of mortality in rheumatoid arthritis-related interstitial lung disease

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) has a heterogeneous clinical presentation and disease course. Establishing prognosis for these patients is challenging. Identifying the factors that predict mortality in patients with RA-ILD could help guide management. A detailed systematic review was conducted in order to identify individual variables that predict mortality in RA-ILD. A literature review was performed using keywords and medical subject headings to identify all articles relating to the prognosis of RA-ILD. Studies were included if they identified predictors of mortality in adults with RA-ILD, were published in English, and included at least 10 patients with RA-ILD. Two authors independently reviewed each citation and extracted data from all studies meeting inclusion criteria. Any differences were then resolved by consensus. A total of 10 studies met our inclusion criteria. All were observational cohort studies of variable quality. Mean age of reported patients ranged from 55 to 69 years, and 41.7% of all patients were male. Median survival ranged from 3.2 to 8.1 years. Significant predictors of mortality on multivariate analysis were older age, male gender, lower diffusion capacity for carbon monoxide, extent of fibrosis, and the presence of usual interstitial pneumonia pattern. Mortality in RA-ILD is associated with several patient- and ILD-specific variables; however, previous studies are of low quality.

Rheumatoid arthritis-associated interstitial lung disease: radiologic identification of usual interstitial pneumonia pattern

PURPOSE

To determine the accuracy of computed tomography (CT) in identifying the histopathologic usual interstitial pneumonia (UIP) pattern in rheumatoid arthritis-associated interstitial lung disease (RA-ILD).

MATERIALS AND METHODS

All patients were enrolled into institutional review board-approved longitudinal cohorts at their respective institution, and informed consent was obtained at the time of enrollment. Images of patients with surgical lung biopsy-proved RA-ILD (n = 69) were collected from three tertiary care centers. Two experienced thoracic radiologists independently reviewed the CT scans. The CT pattern was categorized as definite UIP, possible UIP, or inconsistent with UIP in accordance with published criteria. Findings of biopsies were reviewed by an experienced lung pathologist. The sensitivity and specificity of definite CT UIP pattern to histopathologic UIP pattern were determined. The agreement between radiologists was assessed by calculating a κ score.

RESULTS

The histopathologic UIP pattern was present in 42 of 69 (61%) patients. Men were more likely than women to have a histopathologic UIP pattern (P = .02). Twenty patients (29%, 20 of 69) had a definite UIP pattern on CT scans. The specificity of CT UIP pattern was 96% (26 of 27; 95% confidence interval [CI]: 81%, 100%), with a negative predictive value of 53% (26 of 49). The sensitivity of CT UIP pattern was 45% (19 of 42; 95% CI: 30%, 61%), with a positive predictive value of 95% (19 of 20). The agreement between radiologists for definite UIP pattern versus not was 87% (κ = 0.67, P < .0001).

CONCLUSION

Definite UIP pattern on a CT scan in RA-ILD is highly specific and moderately sensitive for histopathologic UIP pattern. CT can therefore help accurately identify the UIP pattern in RA-ILD.