Clinical characteristics and outcomes of hypersensitivity pneumonitis: a population-based study in China

Use of Mycophenolate mofetil for the treatment of fibrotic hypersensitivity pneumonitis

INTRODUCTION

The optimal treatment of fibrosing hypersensitivity pneumonitis (fHP) is not well understood. The aim of the study was to obtain information about the usefulness of mycophenolate mofetil (MMF) in its treatment.

MATERIAL AND METHODS

Quasi-experimental analysis of patients diagnosed with fHP and treated with MMF for one year, in a single centre. From the start of treatment, data collection was prospective.

RESULTS

Seventy-three patients were included and 58 completed the study. FVC% and DLCO% decreased until starting MMF (year -1 to year 0). After completion of treatment (year 1), FVC% stabilised (p=0.336) and DLCO% improved significantly (p=0.004) compared to year 0. Dyspnoea, number of patients without corticosteroids and mean corticosteroid dose also improved significantly (p<0.001 in all cases). Being male and having a history of tuberculosis were predictors of poor drug response [AUC = 0.89 (95%CI: 0.80-0.98)]. Forty-five adverse effects were observed in 34 patients (46.6%). In 4 cases (5.5%), the adverse effect was severe and required discontinuation of treatment.

CONCLUSIONS

In patients with fHP, MMF improves lung function and dyspnoea and reduces both the number of patients requiring oral corticosteroids and their mean dose in those who completed 1 year of treatment. The model constructed predicts which patients will respond poorly to treatment, with good discriminative ability and only a small percentage of patients will not tolerate treatment. Further prospective, randomised clinical trials are needed to define the role of this treatment in fHP.

Hypersensitivity Pneumonitis: Challenges of a Complex Disease

Hypersensitivity pneumonitis (HP) is a complex interstitial lung disease caused by chronic inhalation of a wide variety of antigens in susceptible and sensitized individuals, commonly associated with an occupational exposure. An impressive number of inciting antigens causing hypersensitivity pneumonitis have been found to cover a wide range of occupations. As working practices have changed over time, especially in industrialized countries, new names for occupational HP have emerged. This review emphasizes the main diagnostic issues arising from the high variability of clinical presentation and the broad spectrum of causal antigens. Furthermore, it provides an overview of current methods to unveil possible causes of hypersensitivity pneumonitis, highlights HP's current diagnostic and treatment challenges and the remaining areas of uncertainty, and presents prevention strategies.

Japanese clinical practice guide 2022 for hypersensitivity pneumonitis

Considering recently published two guidelines for the diagnosis of hypersensitivity pneumonitis (HP), the Japanese Respiratory Society (JRS) has now published its own Japanese clinical practice guide for HP. Major types of HP in Japan include summer-type, home-related, bird-related, farmer's lung, painter's lung, humidifier lung, and mushroom grower's lung. Identifying causative antigens is critical for increasing diagnostic confidence, as well as improving prognosis through appropriate antigen avoidance. This guide proposes a comprehensive antigen questionnaire including the outbreak sources reported in Japan. Drawing on the 2021 CHEST guideline, this guide highlights the antigen identification confidence level and adaptations for environmental surveys. The detection of specific antibodies against causative antigens is an important diagnostic predictor of HP. In Japan, the assessments of bird-specific IgG (pigeons, budgerigars) and the Trichosporon asahii antibody are covered by medical insurance. Although this guide adopts the 2020 ATS/JRS/ALAT guideline diagnostic criteria based on the combination of imaging findings, exposure assessment, bronchoalveolar lavage lymphocytosis, and histopathological findings, it added some annotations to facilitate the interpretation of the content and correlate the medical situation in Japan. It recommends checking biomarkers; seasonal changes in the KL-6 concentration (increase in winter for bird-related HP/humidifier lung and in summer for summer-type HP) and high KL-6 concentrations providing a basis for the suspicion of HP. Antigen avoidance is critical for disease management of HP. This guide also addresses the pharmacological management of HP, highlighting the treatment strategy for fibrotic HP including combination therapies with anti-inflammatory/immunosuppressive and antifibrotic drugs.

Serum Specific Antibodies Do Not Seem to Have an Additional Role in the Diagnosis of Hypersensitivity Pneumonitis

BACKGROUND

We aimed to investigate the contribution of serum IgG testing to the history of exposure in the diagnosis of fibrotic hypersensitivity pneumonitis.

METHODS

A single-center, retrospective, cross-sectional study including 63 patients pathologically diagnosed with fibrotic hypersensitivity pneumonitis in line with the guidelines of the American Thoracic Society. Descriptive statistics were presented and Kappa statistic was performed to evaluate the compatibility between panel and the history of exposure.

RESULTS

The median age was 63 (22-81) years and 34 (54%) were male. Forty-six patients (73%) had a positive history of exposure. Thirty-nine patients (61.9%) had a positive HP/Avian panel. The most common exposure agent was mold (34.9%), followed by parakeet (31.7%). The antibody detected the most was penicillium chrysogenum lgG (36.5%), followed by aspergillus fumigatus (31.8%). There was no compatibility between HP/Avian panel and history of exposure (kappa coefficient= 0.18, p= 0.14). When the exposure was only assessed based on the history, 4 (6.35%) patients were diagnosed as fibrotic hypersensitivity pneumonitis with low confidence, 6 (9.52%) with moderate confidence, 11 (17.46%) with high confidence and 42 (66.67%) with definite confidence; whereas 4 (6.35%) patients were diagnosed as fibrotic hypersensitivity pneumonitis with low confidence, 6 (9.52%) with moderate confidence, 9 (14.29%) patients with high confidence and 44 (69.84%) patients with definite confidence if exposure was evaluated with history and/or panel.

CONCLUSIONS

Serum specific precipitating antibody panel does not seem to provide additional value to the history of exposure in the diagnosis of fibrotic hypersensitivity pneumonitis.

Disease progression in patients with usual interstitial pneumonia and probable UIP patterns on computed tomography with various underlying etiologies: a retrospective cohort study

Background

Usual interstitial pneumonia (UIP) is a pattern of interstitial pneumonia that is caused by different etiologies. This study aimed to investigate the transplant-free survival (TFS) and the decline in forced vital capacity (FVC) of the patients with UIP and probable UIP patterns on CT caused by various underlying conditions.

Methods

A retrospective cohort study was conducted, enrolling patients with interstitial lung disease exhibiting a CT pattern consistent with UIP or probable UIP. Clinical and prognostic data of patients categorized by the etiology were compared.

Results

A total of 591 patients were included and classified into the following groups: idiopathic pulmonary fibrosis (IPF) (n = 320), connective tissue disease (CTD)-UIP (n = 229), asbestosis-UIP (n = 28), and hypersensitivity pneumonitis (HP)-UIP (n = 14). Advanced age, elevated levels of serum cytokeratin fraction 21-1 and percentage of neutrophils in bronchoalveolar lavage were observed in all groups. IPF patients showed a more rapid decline in FVC (133.9 mL/year) compared to CTD-UIP (24.5 mL/year, p = 0.001) and asbestosis-UIP (61.0 mL/year, p = 0.008) respectively. Sub-analysis of CTD-UIP revealed that patients with rheumatoid arthritis (RA)-UIP (88.1 mL/year) or antineutrophil cytoplasmic antibody-associated vasculitis (AAV)-UIP (72.9 mL/year) experienced a faster deterioration in FVC compared to those with primary Sjögren's syndrome (pSS)-UIP (25.9 mL/year, p < 0.05). Kaplan-Meier curves showed that IPF had the poorest TFS (median 55.9 months), followed by HP-UIP (57.5 months), CTD-UIP (66.7 months), and asbestosis-UIP (TFS not reached). RA-UIP or AAV-UIP did not exhibit any prognostic advantages compared to IPF, while asbestosis-UIP and pSS-UIP showed better survival rates.

Conclusion

Patients with UIP caused by different underlying conditions share certain common features, but the trajectories of disease progression and survival outcomes differ.

Evaluation of cases with hypersensitivity pneumonia: 10 year analysis

INTRODUCTION

The aim of this study was to examine the clinical features of hypersensitivity pneumonia (HP) cases, diagnostic methods, and related conditions in our hospital, which is a reference clinic in Turkey for chest disease.

METHODS

The population of this retrospective cross-sectional study consists of all hypersensitivity pneumonia patients followed in a tertiary hospital between 2010 and 2019. The data of 78 patients were included in the analysis. Data were grouped by source of exposure (occupational, environmental, and cryptogenic) by examining the files of the patients.

RESULTS

Occupational risk factors were detected in 29 (37.2%) of the cases, environmental risk factors were found in 24 (30.8%) cases, neither occupational nor environmental risk factors were detected in 25 (32%) cases, and they were evaluated as cryptogenic. The time from the onset of symptoms to diagnosis was 15.8 ± 26.6 months. The time from the onset of symptoms to diagnosis was found to be longer in the group with occupational risk factors compared with the other groups and was statistically significant (0.044).

CONCLUSION

HP is a immune-mediated interstitial lung disease induced by repeated exposure to environmental and occupational antigens. Etiological agent can be detected in HP patients by detailed questioning of occupational and environmental exposure that may be associated with the onset of symptoms in cases with suspected HP.

Risk factors associated with mortality in hypersensitivity pneumonitis: a meta-analysis

BACKGROUND

Hypersensitivity pneumonitis (HP) related deaths have increased substantially in recent years. It is important to identify the risk factors of HP significantly associated with mortality to ensure close patient monitoring and assess disease progression.

RESEARCH DESIGN AND METHODS

Extensive literature search was conducted in accordance with the PRISMA checklist. Literature search of PUBMED, EMBASE and Cochrane Library database between January 2009 and April 2021 using the terms "hypersensitivity pneumonitis", "hazard ratio", and "mortality" identified 325 articles. A total of 22 independent original studies focusing on mortality of HP patients were assessed.

RESULTS

This systematic review and meta-analysis suggests that increased age, male sex, honeycombing and traction bronchiectasis patterns on high-resolution computed tomography (HRCT) images are the major mortality-related risk factors of patients with HP. In case of chronic HP, antigen exposure appeared to be an additional risk factor.

CONCLUSIONS

The clinico-radiological risk factors of mortality identified for HP will enable effective and close monitoring of patients, prognostication and guide towards appropriate management decisions. However, association between the type of antigen and mortality remains to be explored.

Short-term lung function changes predict mortality in patients with fibrotic hypersensitivity pneumonitis

Background and objective

A proportion of patients with fibrotic hypersensitivity pneumonitis (fHP) follow a progressive disease course despite immunosuppressive treatment. Little is known about predictors of mortality in fHP. We aimed to investigate the impact of short‐term lung function changes in fHP on mortality.

Methods

Baseline demographics for 145 consecutive patients with a multi‐disciplinary team diagnosis of fHP, as well as baseline and 1‐year follow‐up of lung function, baseline echocardiographic findings, bronchoalveolar lavage (BAL) cellularity and all‐cause mortality were recorded. Changes in forced vital capacity (FVC) ≥ 5% and ≥10%, and diffusion capacity of the lung for carbon monoxide (DLCO) ≥ 10% and ≥15% at 1 year were calculated. Cox proportional hazards analysis was performed to test for associations with mortality.

Results

Baseline lung function severity, age, presence of honeycombing on computed tomography (CT) and echocardiographic pulmonary arterial systolic pressure (PASP) ≥ 40 mm Hg were associated with early mortality, while BAL lymphocytosis was associated with improved survival. A decline in FVC ≥ 5% (hazard ratio [HR]: 3.10, 95% CI: 2.00–4.81, p < 0.001), FVC ≥ 10% (HR: 3.11, 95% CI: 1.94–4.99, p < 0.001), DLCO ≥ 10% (HR: 2.80, 95% CI: 1.78–4.42, p < 0.001) and DLCO ≥ 15% (HR: 2.92, 95% CI: 1.18–4.72, p < 0.001) at 1 year was associated with markedly reduced survival on univariable and multivariable analyses after correcting for demographic variables, disease severity, honeycombing on CT and treatment, as well as BAL lymphocytosis and PASP ≥ 40 mm Hg on echocardiography, in separate models.

Conclusion

Worsening in FVC and DLCO at 1 year, including a marginal decline in FVC ≥ 5% and DLCO ≥ 10%, is predictive of markedly reduced survival in fHP.

[Comparative pathomorphological characteristics of idiopathic pulmonary fibrosis and fibrotic hypersensitivity pneumonitis]

The paper presents an X-ray morphological differential diagnosis of idiopathic pulmonary fibrosis (IPF) and fibrotic hypersensitivity pneumonitis (FHP). It describes the etiology, pathogenesis, radiological signs, and pathoanatomy of IPF and FHP. For differential diagnosis, radiological and morphological signs were studied in 105 patients with IPF and in 111 patients with FHP. The mean ages of patients with IPF or FHP were 65.0±8.9 and 48.9±12.3 years, respectively. The history of IPF to the moment of its diagnosis ranged from 1 to 18 months, while that of FHP was 35 to 79 days. The authors describe the additional morphological signs of FHP: delicate collagen fibrosis; smooth muscle metaplasia in the interalveolar septa and fibrotic areas; fibroblastic foci mainly in the walls of bronchioles; plasma cell infiltration of interalveolar septa with a touch of neutrophils and eosinophils. A table has been compiled for differential diagnosis according to the morphological signs of IPF and FHP.

NMR metabolomic and microarray-based transcriptomic data integration identifies unique molecular signatures of hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an immune-mediated granulomatous interstitial lung disease (ILD) that results from repeated inhalation of certain antigens. Despite major advances in research, pathophysiology of the disease remains poorly understood. The present study combines metabolomic and transcriptomic data to determine alterations in HP subjects as compared with healthy controls. Metabolic signatures were identified in serum, exhaled breath condensate (EBC) and bronchoalveolar lavage fluid (BALF) of HP patients using proton nuclear magnetic resonance (NMR) metabolomics. The expression of three metabolites, i.e., lactate, pyruvate, and proline, was found to be significantly altered in all three biofluids. The potential of differential diagnosis based on these three metabolites was investigated by including a group of patients with sarcoidosis, which is another type of granulomatous ILD. In addition, differentially expressed transcriptomic fingerprints in blood samples were identified by analyzing a Gene Expression Omnibus (GEO) database. The transcriptomics analysis of these microarray-based data revealed 59 genes to be significantly dysregulated in patients with HP. Over representation analysis of the metabolites and genes of interest was performed using IMPaLA (Integrated Molecular Pathway Level Analysis) version 12. Integrated analysis of serum metabolite signatures and blood gene expression suggests dysregulation of PI3K-AKT signaling and TCA cycle pathways in these patients. This preliminary study is a step towards better understanding of the pathogenesis of HP by identification of differentially expressed metabolites and transcriptomic fingerprints. These molecular signatures may be explored as diagnostic markers for differentiating HP from other lung diseases.

Prognostic Implication of Diagnostic Confidence Level in Patients with Fibrotic Hypersensitivity Pneumonitis

BACKGROUND

Hypersensitivity pneumonitis (HP) has various clinical courses and outcomes, but the prognostic factors are not well-defined. Vasakova et al. [Am J Respir Crit Care Med. 2017 Sep;196(6):680-9] have proposed a diagnostic algorithm that categorized suspected patients according to the level of confidence in the diagnosis. This study aimed to investigate whether the confidence level of clinical diagnosis has prognostic implication in patients with fibrotic HP.

METHODS

This study included 101 biopsy-proven fibrotic HP patients diagnosed between 2002 and 2017. The patients were retrospectively classified into confident, probable, possible, and unlikely chronic HP, according to the confidence level in the diagnostic criteria/algorithm. The survival and forced vital capacity (FVC) changes were compared between the groups. Risk factors for mortality were analysed using a Cox proportional hazard model.

RESULTS

The median follow-up duration was 67.6 months. The mean age was 60.4 years, and percentages of women were 60.4%. When classified based on the diagnostic criteria/algorithm, possible HP was the most common (51.5%), followed by probable (26.7%), confident (9.9%), and unlikely HP (6.9%). Distinctive survival curves were found according to the diagnostic confidence level, showing the worst outcome in unlikely chronic HP (median survival, 30.2 months). In a multivariable Cox analysis, unlikely HP was a significant predictor of poor survival (hazard ratio, 4.652; 95% confidence interval, 1.231-17.586; p = 0.023), after adjustment for age, body mass index, FVC, and diffusing capacity.

CONCLUSIONS

The diagnostic confidence level may predict clinical outcomes in patients with HP. Unlikely HP was shown to have a significantly poorer survival than other diagnostic confidence levels.

Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report

BACKGROUND

The purpose of this analysis is to provide evidence-based and consensus-derived guidance for clinicians to improve individual diagnostic decision-making for hypersensitivity pneumonitis (HP) and decrease diagnostic practice variability.

STUDY DESIGN AND METHODS

Approved panelists developed key questions regarding the diagnosis of HP using the PICO (Population, Intervention, Comparator, Outcome) format. MEDLINE (via PubMed) and the Cochrane Library were systematically searched for relevant literature, which was supplemented by manual searches. References were screened for inclusion, and vetted evaluation tools were used to assess the quality of included studies, to extract data, and to grade the level of evidence supporting each recommendation or statement. The quality of the evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Graded recommendations and ungraded consensus-based statements were drafted and voted on using a modified Delphi technique to achieve consensus. A diagnostic algorithm is provided, using supporting data from the recommendations where possible, along with expert consensus to help physicians gauge the probability of HP.

RESULTS

The systematic review of the literature based on 14 PICO questions resulted in 14 key action statements: 12 evidence-based, graded recommendations and 2 ungraded consensus-based statements. All evidence was of very low quality.

INTERPRETATION

Diagnosis of HP should employ a patient-centered approach and include a multidisciplinary assessment that incorporates the environmental and occupational exposure history and CT pattern to establish diagnostic confidence prior to considering BAL and/or lung biopsy. Criteria are presented to facilitate diagnosis of HP. Additional research is needed on the performance characteristics and generalizability of exposure assessment tools and traditional and new diagnostic tests in modifying clinical decision-making for HP, particularly among those with a provisional diagnosis.

Executive Summary: Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report

BACKGROUND

The purpose of this summary is to provide a synopsis of evidence-based and consensus-derived guidance for clinicians to improve individual diagnostic decision-making for hypersensitivity pneumonitis (HP) and decrease diagnostic practice variability.

STUDY DESIGN AND METHODS

Approved panelists developed key questions regarding the diagnosis of HP using the PICO (Population, Intervention, Comparator, and Outcome) format. MEDLINE (via PubMed) and the Cochrane Library were systematically searched for relevant literature, which was supplemented by manual searches. References were screened for inclusion and vetted evaluation tools were used to assess the quality of included studies, to extract data, and to grade the level of evidence supporting each recommendation or statement. The quality of the evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Graded recommendations and ungraded consensus-based statements were drafted and voted on using a modified Delphi technique to achieve consensus.

RESULTS

The systematic review of the literature based on 14 PICO questions resulted in 14 key action statements: 12 evidence-based, graded recommendations, and 2 ungraded consensus-based statements. All evidence was of very low quality.

INTERPRETATION

Diagnosis of HP should employ a patient-centered approach and include a multidisciplinary assessment that incorporates the environmental and occupational exposure history and CT pattern to establish diagnostic confidence prior to considering BAL and/or lung biopsy. Additional research is needed on the performance characteristics and generalizability of exposure assessment tools and traditional and new diagnostic tests in modifying clinical decision-making for HP, particularly among those with a provisional diagnosis.

Exposure assessment in hypersensitivity pneumonitis: a comprehensive review and proposed screening questionnaire

Hypersensitivity pneumonitis is an immune-mediated inflammatory lung disease characterised by the inhalation of environmental antigens leading to acute and chronic lung injury. Along with suggestive clinical and radiological findings, history and timing of suspected antigen exposure are important elements for diagnostic confidence. Unfortunately, many diagnoses remain tentative and based on vague and imprecise environmental or material exposure histories. To date, there has not been a comprehensive report highlighting the frequency and type of environmental exposure that might lead to or support a more systematic approach to antigen identification. We performed a comprehensive literature review to identify and classify causative antigens and their associated environmental contexts or source materials, with emphasis on the extent of the supportive literature for each exposure type. Eligible publications were those that reported unique inciting antigens and their respective environments or contexts. A clinical questionnaire was then proposed based on this review to better support diagnosis of hypersensitivity pneumonitis when antigen testing or other clinical and radiological variables are inconclusive or incomplete.

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a complex syndrome caused by the inhalation of a variety of antigens in susceptible and sensitized individuals. These antigens are found in the environment, mostly derived from bird proteins and fungi. The prevalence and incidence of HP vary widely depending on the intensity of exposure, the geographical area and the local climate. Immunopathologically, HP is characterized by an exaggerated humoral and cellular immune response affecting the small airways and lung parenchyma. A complex interplay of genetic, host and environmental factors underlies the development and progression of HP. HP can be classified into acute, chronic non-fibrotic and chronic fibrotic forms. Acute HP results from intermittent, high-level exposure to the inducing antigen, usually within a few hours of exposure, whereas chronic HP mostly originates from long-term, low-level exposure (usually to birds or moulds in the home), is not easy to define in terms of time, and may occur within weeks, months or even years of exposure. Some patients with fibrotic HP may evolve to a progressive phenotype, even with complete exposure avoidance. Diagnosis is based on an accurate exposure history, clinical presentation, characteristic high-resolution CT findings, specific IgG antibodies to the offending antigen, bronchoalveolar lavage and pathological features. Complete antigen avoidance is the mainstay of treatment. The pharmacotherapy of chronic HP consists of immunosuppressive drugs such as corticosteroids, with antifibrotic therapy being a potential therapy for patients with progressive disease.

Prognostic factors in chronic hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an immunologically mediated lung disease resulting from exposure to inhaled environmental antigens. Prognosis is variable, with a subset of patients developing progressive fibrosis leading to respiratory failure and death. Therefore, there is an urgent need to identify factors which predict prognosis and survival in patients with HP. We undertook a narrative review of existing evidence to identify prognostic factors in patients with chronic HP. Patient demographics, smoking history, extent of antigen exposure and comorbidities all have reported associations with disease outcome, and physiological, radiological and laboratory markers have been shown to predict overall survival. While no single marker has been demonstrated to accurately and reliably predict prognosis, older age, more severe impairment of pulmonary function at baseline and established fibrosis on either biopsy or high-resolution computed tomography are consistently associated with worse survival. The vast majority of existing studies are retrospective, and this review identifies a need for prospective longitudinal studies with serial assessment of respiratory health to ascertain factors associated with nonfatal deterioration. Future developments, including the development of HP-specific composite scores may help further improve our ability to predict outcomes for individual patients.

Identifying causation in hypersensitivity pneumonitis: a British perspective

Background

Establishing whether patients are exposed to a ‘known cause’ is a key element in both the diagnostic assessment and the subsequent management of hypersensitivity pneumonitis (HP).

Objective

This study surveyed British interstitial lung disease (ILD) specialists to document current practice and opinion in relation to establishing causation in HP.

Methods

British ILD consultants (pulmonologists) were invited by email to take part in a structured questionnaire survey, to provide estimates of demographic data relating to their service and to rate their level of agreement with a series of statements. A priori ‘consensus agreement’ was defined as at least 70% of participants replying that they ‘Strongly agree’ or ‘Tend to agree’.

Results

54 consultants took part in the survey from 27 ILD multidisciplinary teams. Participants estimated that 20% of the patients in their ILD service have HP, and of these, a cause is identifiable in 32% of cases. For patients with confirmed HP, an estimated 40% have had a bronchoalveolar lavage for differential cell counts, and 10% a surgical biopsy. Consensus agreement was reached for 25 of 33 statements relating to causation and either the assessment of unexplained ILD or management of confirmed HP.

Conclusions

This survey has demonstrated that although there is a degree of variation in the diagnostic approach for patients with suspected HP in Britain, there is consensus opinion for some key areas of practice. There are several factors in clinical practice that currently act as potential barriers to identifying the cause for British HP patients.