Detection of indoor and outdoor avian antigen in management of bird-related hypersensitivity pneumonitis

Challenges in the Diagnosis and Management of Fibrotic Hypersensitivity Pneumonitis: A Practical Review of Current Approaches

Recent advances in fibrotic hypersensitivity pneumonitis include improved diagnostic guidance, systematic assessments of immunosuppressive therapy, and the recent availability of antifibrotic therapy (nintedanib) for those with progressive disease. A standardized approach to diagnosis may lead to better inclusion criteria for future therapeutic protocols and delineation of disease or treatment response predictors for real-world management. This review will highlight current diagnostic and treatment challenges and remaining knowledge gaps or areas of uncertainty, with a practical overview of supporting evidence and its clinical implications. Exposure history, serologic testing for antigen sensitivity, bronchoalveolar lavage lymphocytosis, histopathology, and radiologic findings will be covered in the diagnosis section, with immunosuppression, antifibrotic therapy, lung transplantation, and disease prognosis in the treatment and management section.

A rapid test for the environmental detection of pigeon antigen

INTRODUCTION

Avoidance of inhaled bird antigens is essential to prevent hypersensitivity pneumonitis disease progression. The aim of the present study was to develop a sandwich enzyme link immunoassay (ELISA) and an immunochromatographic test (ICT) and compare their ability to detect pigeon antigens in environmental samples.

METHODS

An amplified sandwich ELISA using pigeon serum as a calibration standard and a ICT using gold-labeled anti-pigeon serum antibodies for the rapid detection of pigeon antigens in environmental samples were developed. Twenty-two different airborne samples were collected and analysed using both methods. Strip density values obtained with ICT were calculated and compared with the concentrations determined by the ELISA method for pigeon antigens. Strips results were also visually analysed by five independent evaluators.

RESULTS

The ELISA method to quantify pigeon antigen had a broader range (58.4 and 10,112.2 ng/ml), compared to the ICT assay (420 to 3360 ng/ml). A kappa index of 0.736 (p < 0.0001) was obtained between the observers evaluating the ICT strips. The results of the ELISA and the relative density of the ICT showed a highly significant correlation (rs:0.935; p < 0.0001). Bland-Altman plot also confirmed excellent agreement between the two methods (mean difference: -1.626; p < 0.0001).

CONCLUSIONS

Since there was a good correlation between both assays, we can conclude that the rapid and simple ICT assay is a good and valid alternative, which does not require expensive equipment, for the validated ELISA technique.

Antigen avoidance in people with hypersensitivity pneumonitis: A scoping review

BACKGROUND

Antigen avoidance (AA) is essential for people with hypersensitivity pneumonitis (HP). An intervention programme to promote continuous AA in people with HP will be the focus of future research.

OBJECTIVES

We systematically analysed the AA behaviour of people with HP, interventions of health-care providers to promote AA behaviour, clinical outcomes after AA, and evaluation methods after AA.

METHODS

We conducted a scoping review using six online databases and manual searches. Papers written in English or Japanese that reported cases on AA were selected. The extracted data were classified qualitatively.

RESULTS

In total 205 cases included in 109 eligible papers were examined.

CONCLUSIONS

This review clarified the fundamental evidence of AA in people with HP. These people required the continuous support of health-care providers to continue appropriate AA. This review highlighted four aspects that require further research to design interventions for promoting effective and continuous AA in people with HP.

Assessment and Management of Occupational Hypersensitivity Pneumonitis

The diagnosis and treatment of occupational hypersensitivity pneumonitis (OHP) remain complex and challenging in the absence of diagnostic gold standards or clinical guidelines. This review provides an update of the recent literature regarding the different presentations of OHP and the diagnostic yield and value of the diagnostic tests currently available, which include occupational and medical history, laboratory tests (serum-specific immunoglobulins, environmental sampling), imaging, bronchoalveolar lavage, transbronchial biopsy, transbronchial cryobiopsy, surgical lung biopsy, and specific inhalation challenges. These tools provide a precise differential diagnosis within the framework of interstitial lung diseases. However, among the chronic fibrotic forms, distinguishing OHP from sarcoidosis, nonspecific interstitial pneumonia and idiopathic pulmonary fibrosis remains a diagnostic challenge. Avoidance of exposure is pivotal for OHP management, whereas corticosteroids are fundamental in the pharmacological approach to this disease. In addition, studies describing the long-term benefits of immunosuppressive and antifibrotic agents have increased the use of these treatments in OHP.

Interstitial Lung Disease and Pulmonary Fibrosis: A Practical Approach for General Medicine Physicians with Focus on the Medical History

Interstitial lung disease (ILD) and pulmonary fibrosis comprise a wide array of inflammatory and fibrotic lung diseases which are often confusing to general medicine and pulmonary physicians alike. In addition to the myriad of clinical and radiologic nomenclature used in ILD, histopathologic descriptors may be particularly confusing, and are often extrapolated to radiologic imaging patterns which may further add to the confusion. We propose that rather than focusing on precise histologic findings, focus should be on identifying an accurate etiology of ILD through a comprehensive and detailed medical history. Histopathologic patterns from lung biopsy should not be dismissed, but are often nonspecific, and overall treatment strategy and prognosis are likely to be determined more by the specific etiology of ILD rather than any particular histologic pattern. In this review, we outline a practical approach to common ILDs, highlight important aspects in obtaining an exposure history, clarify terminology and nomenclature, and discuss six common subgroups of ILD likely to be encountered by general medicine physicians in the inpatient or outpatient setting: Smoking-related, hypersensitivity pneumonitis, connective tissue disease-related, occupation-related, medication-induced, and idiopathic pulmonary fibrosis. Accurate diagnosis of these forms of ILD does require supplementing the medical history with results of the physical examination, autoimmune serologic testing, and chest radiographic imaging, but the importance of a comprehensive environmental, avocational, occupational, and medication-use history cannot be overstated and is likely the single most important factor responsible for achieving the best possible outcomes for patients.

Environmental levels of avian antigen are relevant to the progression of chronic hypersensitivity pneumonitis during antigen avoidance

Background

In chronic hypersensitivity pneumonitis (chronic HP), antigen avoidance is critical for disease management; however, complete avoidance is difficult because of unrecognized exposure to antigens. Recently, we revealed that the amount of avian antigen (AAA) in household dust at the time of diagnosis predicted the progression of chronic bird‐related HP. The purpose of this study is to evaluate the relationship between the prognosis of chronic bird‐related HP and the AAA that remained in the environment during antigen avoidance.

Methods

First, we measured the AAA in household dust of 28 consecutive patients (22 with chronic bird‐related HP and 6 with acute bird‐related HP) and 12 healthy volunteers. Second, we measured the AAA and collected questionnaires on the environmental conditions of the homes of 53 patients with various lung diseases, including bird‐related HP, to investigate the environmental parameters related to a higher AAA. Finally, we prospectively recruited 14 consecutive patients with chronic bird‐related HP, measured the AAA periodically, and collected clinical data.

Results

The AAA was higher in patients with chronic bird‐related HP at the time of diagnosis compared to healthy volunteers and was highest in patients with acute bird‐related HP. Logistic regression analysis showed that birds frequenting a residence was the only significant factor for a higher AAA (odds ratio, 5.686; 95%CI, 1.263–25.59; P = 0.024). There was a correlation between the mean AAA and decline of vital capacity for 1 year (r = −0.55; 95%CI −0.84 to −0.01; P = 0.043).

Conclusion

Measurements of the AAA after diagnosis predict the progression of chronic bird‐related HP. Avian antigen can exist in the indoor environment regardless of antigen avoidance. The presence of avian antigen in the indoor environment can be attributed to wild birds found outdoors.

The amount of avian antigen in household dust predicts the prognosis of chronic bird-related hypersensitivity pneumonitis

RATIONALE

Bird-related hypersensitivity pneumonitis is induced by inhalation of avian antigen. Evaluation to avoid repeated exposure to avian antigen is a key part of the treatment for bird-related hypersensitivity pneumonitis. It can be difficult, however, to reliably evaluate exposure to the antigen because bird-related hypersensitivity pneumonitis in its chronic form may be caused by unrecognized and indirect exposure.

OBJECTIVE

The purpose of the present study is to establish a method for measuring environmental avian antigen in patients with chronic bird-related hypersensitivity pneumonitis and to evaluate the clinical utility of the method.

METHODS

The amount of avian antigen was measured in samples of dust collected from the household environments of patients with chronic bird-related hypersensitivity pneumonitis. The patients whose clinical progress could be followed by periodic pulmonary function tests for 1 year were classified into a deterioration group and a stable group. Age, sex, smoking status, FVC % predicted, and the amount of avian antigen in household dust samples at the diagnosis of bird-related hypersensitivity pneumonitis, as well as survival, were determined and evaluated for each group. The total number of subjects was 23.

MEASUREMENTS AND MAIN RESULTS

The clinical condition deteriorated in 11 patients and remained stable in 12. The amount of avian antigen in household dust samples was significantly higher for the deterioration group than for the stable group. In logistic regression analysis, avian antigen was the only variable found to be significant for distinguishing between the two groups. The patients with higher amounts household dust avian antigen had a poor prognosis in the survival analysis. Avian antigen was the only variable to significantly influence the prognosis of chronic bird-related hypersensitivity pneumonitis.

CONCLUSIONS

The levels of exposure to avian antigen were related to disease progression and prognosis in chronic bird-related hypersensitivity pneumonitis.

Pitfalls in diagnosis and management of hypersensitivity pneumonitis

PURPOSE OF REVIEW

Hypersensitivity pneumonitis is a complex syndrome characterized by a combination of inflammation and fibrosis located in both the airways and the lung parenchyma. Both diagnosis and treatment are a real challenge for physicians. This review will focus on recent developments in this emerging field; furthermore, we will emphasize major gaps in the current knowledge, to stimulate further research in this field.

RECENT FINDINGS

The main diagnostic issue is not to miss the entity as the clinical presentation is extremely variable even as the nature of the causal antigen. This article provides an overview of current ways to uncover possible causes of hypersensitivity pneumonitis. A problem of another kind is treatment of this disorder. Crucial in treatment is antigen avoidance, often in combination with immunosuppressive agents. The treatment of acute forms is rather straightforward, but the biggest endeavour, however, is treatment of chronic forms of hypersensitivity pneumonitis, which not always respond to immunosuppressive agents. Therefore, new initiatives should be taken in order to help clinicians in making a proper diagnosis and develop more efficacious treatment especially for patients suffering from chronic hypersensitivity pneumonitis.

SUMMARY

Diagnosis and treatment of hypersensitivity pneumonitis remain a real challenge; this article provides an overview of our current understanding and points out new opportunities for further research.

Management of hypersensivity pneumonitis

Hypersensitivity pneumonitis (HP) is an interstitial lung disease due to a combined type III and IV reaction with a granulomatous inflammation, caused by cytotoxic delayed hypersensitivity lymphocytes, in a Th1/Th17 milieu, chaperoned by a deficient suppressor function of T regulatory cells. Skewing toward a Th2 phenotype is reported for chronic HP. Phenotypic expression and severity depends on environmental and/or host genetic and immune co-factors. The wide spectrum of causative antigens is continuously up-dated with new sources of airborne organic particles and drug-induced HP. The diagnosis requires a detailed history, measurement of environmental exposure, pulmonary function tests, imaging, detection of serum specific antibodies, broncho-alveolar lavage, antigen-induced lymphocyte proliferation, environmental or laboratory-controlled inhalation challenge and lung biopsy. Complete antigen avoidance is the best therapeutic measure, although very difficult to achieve in some cases. Systemic steroids are of value for subacute and chronic forms of HP, but do not influence long term outcome. Manipulation of the immune response in HP holds future promise.