Clinical behaviour of patients exposed to organic dust and diagnosed with idiopathic pulmonary fibrosis

Respiratory Diseases Associated With Organic Dust Exposure

Organic dusts are complex bioaerosol mixtures comprised of dust and par ticulate matter of organic origin. These include components from bacteria, fungi, pollen, and viruses to fragments of animals and plants commonplace to several environmental/occupational settings encompassing agriculture/farming, grain processing, waste/recycling, textile, cotton, woodworking, bird breeding, and more. Organic dust exposures are linked to development of chronic bronchitis, chronic obstructive pulmonary disease, asthma, asthma-like syndrome, byssinosis, hypersensitivity pneumonitis, and idiopathic pulmonary fibrosis. Risk factors of disease development include cumulative dust exposure, smoking, atopy, timing/duration, and nutritional factors. The immunopathogenesis predominantly involves Toll-like receptor signaling cascade, T-helper 1/T-helper 17 lymphocyte responses, neutrophil influx, and potentiation of manifestations associated with allergy. The true prevalence of airway disease directly attributed to organic dust, especially in a workplace setting, remains challenging. Diagnostic confirmation can be difficult and complicated by hesitancy from workers to seek medical care, driven by fears of potential labor-related consequence. Clinical respiratory and systemic presentations coupled with allergy testing, lung function patterns of obstructive versus restrictive disease, and radiological characteristics are typically utilized to delineate these various organic dust-associated respiratory diseases. Prevention, risk reduction, and management primarily focus on reducing exposure to the offending dust, managing symptoms, and preventing disease progression.

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.

Integrating Clinical Probability into the Diagnostic Approach to Idiopathic Pulmonary Fibrosis: An International Working Group Perspective

BACKGROUND

When considering the diagnosis of idiopathic pulmonary fibrosis (IPF), experienced clinicians integrate clinical features that help to differentiate IPF from other fibrosing interstitial lung diseases, thus generating a "pre-test" probability of IPF. The aim of this international working group perspective was to summarize these features using a tabulated approach similar to chest HRCT and histopathologic patterns reported in the international guidelines for the diagnosis of IPF, and to help formally incorporate these clinical likelihoods into diagnostic reasoning to facilitate the diagnosis of IPF.

METHODS

The committee group identified factors that influence the clinical likelihood of a diagnosis of IPF, which was categorized as a pre-test clinical probability of IPF into "high" (70-100%), "intermediate" (30-70%), or "low" (0-30%). After integration of radiological and histopathological features, the post-test probability of diagnosis was categorized into "definite" (90-100%), "high confidence" (70-89%), "low confidence" (51-69%), or "low" (0-50%) probability of IPF.

FINDINGS

A conceptual Bayesian framework was created, integrating the clinical likelihood of IPF ("pre-test probability of IPF") with the HRCT pattern, the histopathology pattern when available, and/or the pattern of observed disease behavior into a "post-test probability of IPF". The diagnostic probability of IPF was expressed using an adapted diagnostic ontology for fibrotic interstitial lung diseases.

INTERPRETATION

The present approach will help incorporate the clinical judgement into the diagnosis of IPF, thus facilitating the application of IPF diagnostic guidelines and, ultimately improving diagnostic confidence and reducing the need for invasive diagnostic techniques.

Interstitial pneumonia with autoimmune features: challenges and controversies

The presence of clinical, serological and/or radiological features suggestive, but not confirmatory, of a defined connective tissue disease in patients with interstitial lung disease is a relatively frequent occurrence. In 2015, the European Respiratory Society and the American Thoracic Society proposed classification criteria for the interstitial pneumonia with autoimmune features (IPAF) research entity to capture such patients in a standardised manner, with the intention of nurturing clinical research. This initiative resulted in the publication of several series of IPAF patients, with significant variation between cohorts in clinical characteristics, outcome and the application of IPAF criteria in patient selection. From this increasing body of published work, it has become apparent that revision of IPAF criteria is now required in order to justify the eventual designation of IPAF as a standalone diagnostic term, as opposed to a provisional entity put forward as a basis for clinical research. This review covers the current state of IPAF, conclusions that can and cannot be drawn from the IPAF evidence base, and ongoing uncertainties that require further expert group consideration.

Occupational exposures and idiopathic pulmonary fibrosis

PURPOSE OF REVIEW

A recent meta-analysis of data from international case-control studies reports a population attributable fraction of 16% for occupational factors in the cause of idiopathic pulmonary fibrosis (IPF). Smoking, genetic factors and other prevalent diseases only partly explain IPF, and so this review aims to summarize recent progress in establishing which occupational exposures are important in cause.

RECENT FINDINGS

IPF is a rare disease, although it is the commonest idiopathic interstitial pneumonia. Epidemiological study suggests that incidence of IPF is increasing, particularly in older men. There are significant associations with IPF and occupational exposures to organic dust, including livestock, birds and animal feed, metal dust, wood dust and silica/minerals. Estimates of effect vary between studies, and are influenced by the distribution of employment, study design and case definition. Inhalation of asbestos fibres is a known cause of usual interstitial pneumonia (as seen histologically in IPF), though there are significant linear relationships between asbestos consumption, and mortality from both IPF and mesothelioma, leading to the hypothesis that low-level asbestos exposure may cause IPF.

SUMMARY

Research must focus on exposure-response relationships between asbestos and other occupational inhaled hazards, and IPF. Funding bodies and policy makers should acknowledge the significant occupational burden on IPF.

Characteristics and Prevalence of Domestic and Occupational Inhalational Exposures Across Interstitial Lung Diseases

BACKGROUND

Inhalational exposures are increasingly recognized as contributing factors in interstitial lung disease (ILD). However, the characteristics of both exposures and exposed patients are not well understood. We hypothesized that domestic and occupational inhalational exposures would be common and associated with differences in demographics, clinical characteristics, and transplant-free survival in patients with all forms of ILD.

RESEARCH QUESTION

What is the prevalence of inhalational exposures across all ILD diagnoses, and are these exposures associated with differences in demographics, clinical characteristics, and transplant-free survival?

STUDY DESIGN AND METHODS

Patients from a tertiary ILD clinic underwent an interview designed to capture inhalational exposures including occupational, home, hobbies, and tobacco. Demographic and survival data were collected from the electronic medical record. Survival analysis was performed using Cox regression to compare exposed vs unexposed patients and adjusted for gender-age-physiology score and smoking.

RESULTS

One hundred and fifty-six patients seen between May and October 2018 were analyzed. Patients had a wide variety of multidisciplinary diagnoses, with a minority of patients with hypersensitivity pneumonitis (14%). One hundred and one patients (65%) had potentially relevant inhalational exposures. More men than women had a history of any exposure (82% vs 51%; P < .001), occupational exposure (66% vs 14%, P < .001), and multiple exposures (56% vs 26%, P < .001), respectively. White race was associated with bird and hobby exposure. Patients with any exposure had worse transplant-free survival (unadjusted hazard ratio, 2.58; 95% CI, 1.13-5.92; P = .025), but this was not statistically significant after adjustment (hazard ratio, 1.82; 95% CI, 0.77-4.27; P = .17).

INTERPRETATION

A standardized interview revealed most patients across all types of ILD had potentially relevant inhalational exposures. Exposures were markedly different based on demographics and were associated with worse transplant-free survival, but this survival difference was not significant after multivariable adjustment. Identification and avoidance of exposures represent actionable targets in ILD management.

Identification and Remediation of Environmental Exposures in Patients With Interstitial Lung Disease: Evidence Review and Practical Considerations

A relationship between inhalational exposure to materials in the environment and development of interstitial lung disease (ILD) is long recognized. Hypersensitivity pneumonitis is an environmentally -induced diffuse parenchymal lung disease. In addition to hypersensitivity pneumonitis, domestic and occupational exposures have been shown to influence onset and progression of other ILDs, including idiopathic interstitial pneumonias such as idiopathic pulmonary fibrosis. A key component of the clinical evaluation of patients presenting with ILD includes elucidation of a complete exposure history, which may influence diagnostic classification of the ILD as well as its management. Currently, there is no standardized approach to environmental evaluation or remediation of potentially harmful exposures in home or workplace environments for patients with ILD. This review discusses evidence for environmental contributions to ILD pathogenesis and draws on asthma and occupational medicine literature to frame the potential utility of a professional evaluation for environmental factors contributing to the development and progression of ILD. Although several reports suggest benefits of environmental assessment for those with asthma or certain occupational exposures, lack of information about benefits in broader populations may limit application. Determining the feasibility, long-term outcomes, and cost-effectiveness of environmental evaluation and remediation in acute and chronic ILDs should be a focus of future research.

Diagnostic approach of fibrosing interstitial lung diseases of unknown origin

Interstitial lung diseases encompass a broad range of numerous individual conditions, some of them characterized histologically by fibrosis, especially idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, chronic hypersensitivity pneumonia, interstitial lung disease associated with connective tissue diseases, and unclassifiable interstitial lung disease. The diagnostic approach relies mainly on the clinical evaluation, especially assessment of the patient's demographics, history, smoking habits, occupational or domestic exposures, use of drugs, and on interpretation of high-quality HRCT of the chest. Imaging is key to the initial diagnostic approach, and often can confirm a definite diagnosis, particularly a diagnosis of idiopathic pulmonary fibrosis when showing a pattern of usual interstitial pneumonia in the appropriate context. In other cases, chest HRCT may orientate toward an alternative diagnosis and appropriate investigations to confirm the suspected diagnosis. Autoimmune serology helps diagnosing connective disease. Indications for bronchoalveolar lavage and for lung biopsy progressively become more restrictive, with better considerations for their discriminate value, of the potential risk associated with the procedure, and of the anticipated impact on management. Innovative techniques and genetics are beginning to contribute to diagnosing interstitial lung disease and to be implemented routinely in the clinic. Multidisciplinary discussion, enabling interaction between pulmonologists, chest radiologists, pathologists and often other healthcare providers, allows integration of all information available. It increases the accuracy of diagnosis and prognosis prediction, proposes a first-choice diagnosis, may suggest additional investigations, and often informs the management. The concept of working diagnosis, which can be revised upon additional information being made available especially longitudinal disease behaviour, helps dealing with diagnostic uncertainty inherent to interstitial lung diseases and facilitates management decisions. Above all, the clinical approach and how thoroughly the patient's history and possible exposures are assessed determine the possibility of an accurate diagnosis.

[The effect of air pollution in diffuse interstitial lung disease]

Few studies have examined the effects of air pollution in diffuse interstitial lung disease and they have focused on small numbers of patients. Most data are available in idiopathic pulmonary fibrosis and studies suggest that the level of exposure to pollutants may influence the development of acute exacerbations (ozone and NO₂), their incidence (NO₂), decline in respiratory function (PM₁₀) and death (PM₁₀ and PM_2.5). Several studies show an increase in the incidence of rheumatoid arthritis in people living near busy roads. In systemic scleroderma, hypersensitivity pneumonitis and sarcoidosis although negative effects of pollution have been reported the data are insufficient to be conclusive. Nevertheless, the observed effects of air pollution are consistent with those described for other chronic respiratory diseases. Exposure to pollution induces oxidative stress, chronic inflammation and shortening of telomeres, which are all mechanisms described in fibrogenesis. New epidemiological studies are needed with individual measurements of exposure to outdoor and indoor pollution, as well as fundamental studies to clarify the effect of pollution on fibrogenesis.

Idiopathic pulmonary fibrosis and occupational risk factors

Idiopathic pulmonary fibrosis (IPF) is a rare lung disease of unknown origin that rapidly leads to death. However, the rate of disease progression varies from one individual to another and is still difficult to predict. The prognosis of IPF is poor, with a median survival of three to five years after diagnosis, without curative therapies other than lung transplantation. The factors leading to disease onset and progression are not yet completely known. The current disease paradigm is that sustained alveolar epithelial micro-injury caused by environmental triggers (e.g., cigarette smoke, microaspiration of gastric content, particulate dust, viral infections or lung microbial composition) leads to alveolar damage resulting in fibrosis in genetically susceptible individuals. Numerous epidemiological studies and case reports have shown that occupational factors contribute to the risk of developing IPF. In this perspective, we briefly review the current understanding of the pathophysiology of IPF and the importance of occupational factors in the pathogenesis and prognosis of the disease. Prompt identification and elimination of occult exposure may represent a novel treatment approach in patients with IPF.

Interstitial Pneumonia With Autoimmune Features (IPAF)

A significant proportion of patients with interstitial lung disease (ILD) manifest autoimmune features, but do not fulfill the diagnostic criteria for a definite connective tissue disease (CTD). In 2015, the European Respiratory Society (ERS) and American Thoracic Society (ATS) “Task Force on undifferentiated Forms of connective tissue disease-associated interstitial lung disease” proposed classification criteria for a so-called research category of Interstitial Pneumonia with Autoimmune Features (IPAF). These classification criteria were based on a combination of features from three domains: a clinical domain consisting of extra-thoracic features; a serologic domain with specific autoantibodies; and a morphologic domain with imaging patterns, histopathological findings or multi-compartment involvement. Patients meeting IPAF criteria tend to have a history of smoking similar to patients with idiopathic pulmonary fibrosis. The most frequent clinical and serological markers of autoimmune features are Raynaud' phenomenon and positive antinuclear antibodies, respectively. Non-specific interstitial pneumonia is the predominant radiologic and histopathologic pattern, although patients meeting IPAF criteria through the clinical and serologic domains may also have a usual interstitial pneumonia pattern. Management should be carefully individualized on a case-by-case basis in keeping with the wide heterogeneity of IPAF and lack of evidence in this particular subgroup of patients. Prognosis is generally intermediate between that of idiopathic pulmonary fibrosis and connective tissue disease-associated interstitial lung disease, but substantially variable according to the predominant histologic and radiologic patterns. As acknowledged by the Task Force, the proposed classification scheme of IPAF is a research concept that will need revision and refinement based on data to better inform prognostication and patient care.

Antifibrotic treatment response and prognostic predictors in patients with idiopathic pulmonary fibrosis and exposed to occupational dust

Background

Idiopathic Pulmonary Fibrosis (IPF) is an aggressive interstitial lung disease with an unpredictable course. Occupational dust exposure may contribute to IPF onset, but its impact on antifibrotic treatment and disease prognosis is still unknown. We evaluated clinical characteristics, respiratory function and prognostic predictors at diagnosis and at 12 month treatment of pirfenidone or nintedanib in IPF patients according to occupational dust exposure.

Methods

A total of 115 IPF patients were recruited. At diagnosis, we collected demographic, clinical characteristics, occupational history. Pulmonary function tests were performed and two prognostic indices [Gender, Age, Physiology (GAP) and Composite Physiologic Index (CPI)] calculated, both at diagnosis and after the 12 month treatment. The date of long-term oxygen therapy (LTOT) initiation was recorded during the entire follow-up (mean = 37.85, range 12–60 months).

Results

At baseline, patients exposed to occupational dust [≥ 10 years (n = 62)] showed a lower percentage of graduates (19.3% vs 54.7%; p = 0.04) and a higher percentage of asbestos exposure (46.8% vs 18.9%; p 0.002) than patients not exposed [< 10 years (n = 53)]. Both at diagnosis and after 12 months of antifibrotics, no significant differences for respiratory function and prognostic predictors were found. The multivariate analysis confirmed that occupational dust exposure did not affect neither FVC and DLCO after 12 month therapy nor the timing of LTOT initiation.

Conclusion

Occupational dust exposure lasting 10 years or more does not seem to influence the therapeutic effects of antifibrotics and the prognostic predictors in patients with IPF.

Electronic supplementary material

The online version of this article (10.1186/s12890-019-0930-7) contains supplementary material, which is available to authorized users.

Idiopathic pulmonary fibrosis: unmasking cryptogenic environmental factors

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease of unknown origin that is associated with high morbidity and mortality. In this perspective, we briefly review the current understanding of the pathophysiology of IPF and the importance of environmental triggers as a precipitant of disease. We discuss occult intrinsic and extrinsic environmental factors that affect the lung microenvironment and may contribute to the development and progression of disease. The clinical implications of this framework need to be further elucidated, because prompt identification and elimination of occult exposures may represent a novel treatment modality.

The Role of Occupational and Environmental Exposures in the Pathogenesis of Idiopathic Pulmonary Fibrosis: A Narrative Literature Review

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease characterised by a progressive and irreversible decline in lung function, which is associated with poor long-term survival. The pathogenesis of IPF is incompletely understood. An accumulating body of evidence, obtained over the past three decades, suggests that occupational and environmental exposures may play a role in the development of IPF. This narrative literature review aims to summarise current understanding and the areas of ongoing research into the role of occupational and environmental exposures in the pathogenesis of IPF.