Detection of specific antibodies to pigeon serum and bloom antigens by enzyme linked immunosorbent assay in pigeon breeder's disease

Longitudinal changes in serum immunoglobulin G testing in patients with fibrotic avian hypersensitivity pneumonitis

BACKGROUND

Evaluation of the antigen responsible for fibrotic hypersensitivity pneumonitis (HP) is challenging. Serum immunoglobulin (Ig) G testing against HP-associated antigens is performed. Although single-serum IgG testing has been investigated, multiple-serum IgG testing has not yet been studied.

METHODS

This study included patients who underwent histopathological examination and positive inhalation challenge test as well as those with moderate or high HP guideline confidence level. Serum IgG testing against pigeon serum was conducted twice using two methods: enzyme linked-immunosorbent assay (ELISA) and ImmunoCAP. The association between changes in serum IgG antibody titers and changes in forced vital capacity (FVC) and other parameters was investigated.

RESULTS

In this study, 28 patients (mean age, 64.5 years; mean FVC, 85.3%) with fibrotic avian HP were selected, of whom 20 and 8 underwent surgical lung biopsy and transbronchial lung cryobiopsy, respectively. Of the 28 patients, 19 had been keeping birds for more than 6 months. A correlation was observed between the annual changes in serum IgG antibody titers by ELISA and changes in relative FVC (r =  - 0.6221, p < 0.001). Furthermore, there was a correlation between the annual changes in serum IgG antibody titers by ImmunoCAP and changes in relative FVC (r =  - 0.4302, p = 0.022). Multiple regression analysis revealed that the change in serum IgG antibody titers by both ELISA and ImmunoCAP also influenced the relative FVC change (p = 0.012 and p = 0.015, respectively). Moreover, 13 patients were given additional treatments between the first and second blood test; however, the additional treatment group was not significantly different in relative FVC change compared to the group with no additional treatment (p = 0.982).

CONCLUSIONS

In patients with fibrotic avian HP, the annual changes in serum IgG testing were correlated with FVC changes, highlighting the importance of serum IgG testing over time.

Sensitization to avian and fungal proteins in different work environments

INTRODUCTION

Hypersensitivity pneumonitis (HP) is usually caused by the inhalation of avian and fungal proteins. The present study assesses a cohort of Urban Pest Surveillance and Control Service (UPSCS) workers with high exposure to avian and fungal antigens, in order to identify their degree of sensitization and the potential risk of developing HP.

METHODS

Workers were divided according to their work activity into Nest pruners (Group 1) and Others (Group 2). All individuals underwent a medical interview, pulmonary function tests and the determination of specific IgG antibodies. Antigenic proteins of pigeon sera were analysed using two-dimensional immunoblotting. Proteins of interest were sequenced by liquid-chromatography-mass spectrometry (LC-MS).

RESULTS

101 workers were recruited (76 men, average age: 42 yrs); (Group 1 = 41, Group 2 = 60). Up to 30% of the study population exhibited increased levels of IgGs to pigeon, small parrot and parrot, and up to 60% showed high levels of Aspergillus and Penicillium IgGs. In Group 1, specific parakeet and Mucor IgGs were higher (p = 0.044 and 0.003 respectively) while DLCO/VA% were lower (p = 0.008) than in Group 2. Two-dimensional immunoblotting showed protein bands of 20-30 KDa recognized by HP patients but not by workers. LC-MS analysis identified Ig Lambda chain and Apolipoprotein A-I as candidate proteins for distinguishing HP patients from exposed workers.

CONCLUSIONS

Two pigeon proteins were identified that may play a role in the development of pathological differences between HP patients and exposed workers. DLCO/VA may have a predictive value in the development of HP disease.

Immunopathological Mechanisms of Bird-Related Hypersensitivity Pneumonitis

Bird-related hypersensitivity pneumonitis (BRHP) is an interstitial lung disease induced by avian proteins. The immunopathological pathways involved in the disease are still unknown. This study assesses the cellular immune response and the cytokine pattern in a mouse model of BRHP. On days -3 and -1, mice were intraperitoneally sensitized with commercial pigeon serum (PS) or saline. Intranasal instillations with PS or saline were carried out on three consecutive days/week over either 3 weeks (Group 1) or 12 weeks (Group 2). Leukocyte and cytokine patterns in lung tissue and pulmonary inflammation in bronchoalveolar lavage (BAL) were analysed. Both groups presented increases in resident monocytes, interstitial macrophages and type 2 dendritic cells (DCs), but also reductions in inflammatory monocytes, alveolar macrophages and tolerogenic DCs compared with their control groups. Group 1 had increased levels of eosinophils and T cells with reductions in neutrophils and B cells, while Group 2 showed high levels of B cells. Both groups exhibited increases in Th1 and Th2 cytokines. Group 2 also showed increased levels of IL-23, a Th17 cytokine. Increased levels of neutrophils, eosinophils and lymphocytes were observed in BAL samples of both groups compared with controls. In the first stages of BRHP, there is a mixed Th1/Th2 immune response, while during the progression of the disease, although there is a Th1 response, the cytokine levels seem to indicate a switch towards a Th2/Th17 mixed response.

Pediatric Hypersensitivity Pneumonitis: Clinicopathologic Characteristics of Two Cases with Fungal Triggers

Background Hypersensitivity pneumonitis (HP) infrequently presents in childhood. Asthma or a pneumonia-like clinical presentation may lead to diagnostic delay, especially in children. Case Report: We present two cases of HP, a 6-year-old (Case 1) male and a 5-year-old (Case 2) female. Both cases had a negative infectious work-up and patchy ground glass lung opacities on chest computed tomography. Lung biopsies demonstrated lymphocytic bronchiolitis with granulomatous interstitial and peribronchial inflammation. Serology demonstrated elevated immunoglobulin precipitins toward Thermoactinomyces and Aspergillus species in Case 1 and Aspergillus fumigatus in Case 2. Both patients received steroid therapy and had symptom resolution. Conclusions: A diagnosis of HP should be considered in pediatric lung biopsies with granulomatous interstitial and peribronchial inflammation, if infectious etiologies are excluded. Integration of clinical, radiological, and laboratory findings can facilitate a timely diagnosis.

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.

Barriers to antigen detection and avoidance in chronic hypersensitivity pneumonitis in the United States

Background

Chronic hypersensitivity pneumonitis (CHP) is an interstitial lung disease (ILD) caused by long term exposure to an offending antigen. Antigen avoidance is associated with improved outcomes. We are unable to identify the antigen source in approximately half of patients. When an antigen is successfully identified, patients have difficulty with avoidance.

Methods

We conducted three structured group discussions with US based ILD specialists utilizing the nominal group technique (NGT). Participants listed barriers to antigen detection and avoidance in CHP. Each participant ranked what they perceived to be the top three barriers in the list in terms of importance. The master list of barriers was consolidated across the three groups into themes that were prioritized based on receiving the highest rankings by participants.

Results

Twenty-five physicians participated; 56% had experience caring for CHP patients for ≥ 16 years. Sixty barriers to antigen detection were categorized into seven themes of which the top three were: 1. unclear significance of identified exposures; 2. gaps in clinical knowledge and testing capabilities; 3. there are many unknown and undiscovered antigens. Twenty-eight barriers to antigen avoidance were categorized into five themes of which the top three were: 1. patient limitations, financial barriers and lack of resources; 2. individual patient beliefs, emotions and attachments to the antigen source; and 3. gaps in clinical knowledge and testing capabilities.

Conclusions

This study uncovered challenges at the individual patient, organizational, and societal levels and ranked them in terms of level of importance. These findings provide information to guide development and validation of multidisciplinary support and interventions geared towards antigen identification and avoidance in CHP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01817-6.

Questionnaires or Serum Immunoglobulin G Testing in the Diagnosis of Hypersensitivity Pneumonitis among Patients with Interstitial Lung Disease

Rationale: Hypersensitivity pneumonitis (HP) results from exposure to a variety of stimuli, which are challenging to identify. Questionnaires and serum immunoglobulin G (IgG) testing are methods to identify potentially causative exposures.Objectives: To perform a systematic review to determine the usefulness of questionnaires and serum IgG testing in identifying exposures that may have caused HP.Methods: This systematic review informed an international, multidisciplinary panel that developed a clinical practice guideline on the diagnosis of HP for the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax. MEDLINE, the Cochrane Library, and EMBASE were searched from January 1946 to October 2019 for studies that used a questionnaire or serum IgG testing to identify exposures that may have caused HP. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to appraise the quality of the evidence.Results: Searches identified 1,141 and 926 potentially relevant articles for questionnaires and serum IgG testing, respectively. The full texts of 32 and 49 articles, respectively, were reviewed. Two observational studies for questionnaires and 15 accuracy studies for serum IgG testing were selected. Questionnaires were better at detecting potentially relevant exposures than clinical history (100% vs. 26%; risk ratio [RR], 3.80; 95% confidence interval [95% CI], 1.79-8.06) and serum IgG testing (100% vs. 63%; RR, 1.58; 95% CI, 1.12-2.23) but did not differ from serum IgG testing plus bronchial challenge testing (59% vs. 65%; RR, 0.90; 95% CI, 0.65-1.24). Longer, detailed questionnaires were more likely to lead to identification of potential exposures. Only 70% of potential exposures identified by questionnaires were subsequently confirmed by environmental testing. Serum IgG testing distinguished HP from healthy exposed and unexposed control subjects with high sensitivity (90% and 92%, respectively) and high specificity (91% and 100%, respectively) but did not distinguish HP as effectively from interstitial lung diseases (ILDs; sensitivity of 83% and specificity of 68%).Conclusions: Using a questionnaire may help clinicians identify potentially relevant exposures when evaluating a patient with newly identified ILD for HP. Serum IgG testing may also lead to identification of potentially relevant exposures, but its usefulness for distinguishing HP from other types of ILD is poor.

Pilot Study Using Recombinant Antigens r-PROE and r-IGLL1 for the Serodiagnosis of Feather Duvet Lung

BACKGROUND

Feather duvet lung (FDL) is an underestimated form of acute and chronic hypersensitivity pneumonitis. Serological tests for FDL need to be validated. We investigated the ability of recombinant pigeon Proproteinase E (r-PROE) and Immunoglobulin-lambda-like-polypeptide-1 (r-IGLL1) proteins to support the serological diagnosis of FDL, and propose them as a serological tool for clinicians to differentiate cases from FDL and Bird fancier's lung (BFL).

METHODS

Specific IgG antibodies against r-PROE and r-IGLL1, analyzed with ELISA, were measured in patients diagnosed with FDL (n=31), BFL (n=15) controls exposed (n=15) and unexposed to feathers (n=15).

RESULTS

The sensitivity and specificity of the r-PROE ELISA for the serological diagnosis of FDL cases versus exposed and unexposed controls were 74.2% and 86.7% respectively, with an index threshold of 0.5 (AUC: 0.89). In addition, this serological test was effective to support the serological diagnosis of FDL and BFL cases with significantly different thresholds. The r-IGLL1 ELISA was only effective for the serological diagnosis of BFL. Also, these two serological tests were useful for the diagnosis of both chronic and acute forms.

CONCLUSIONS

The new diagnostic test for FDL using r-PROE protein should help to detect overt and hidden cases of FDL. The combination of both test will help the clinician in distinguish between the etiology of birds or feathers duvet.

An update on hypersensitivity pneumonitis: what a clinician wants to know

PURPOSE OF REVIEW

A recent international collaboration has updated the clinical definition and diagnostic recommendations for hypersensitivity pneumonitis, focusing on fibrotic and non-fibrotic phenotypes. However, how these transfer to clinical practice and their impact upon clinical management and prognosis of hypersensitivity pneumonitis is unclear. This review will focus on recent advances in the understanding of the clinical aspects of hypersensitivity pneumonitis, predominantly its epidemiology, diagnosis, classification and treatment.

RECENT FINDINGS

Hypersensitivity pneumonitis is a rare disease within the general population, with variable geographical incidence because of environmental, cultural and occupational factors. Confidence in diagnosis relies upon the presence of clinical features with a temporal relationship to an associated exposure, radiological and histopathological features, bronchiolo-alveolar lavage lymphocytosis and precipitating antibodies/specific immunoglobulin G to antigens. Although emerging evidence regarding nintedanib use in progressive fibrotic interstitial lung disease is promising, the majority of therapies (corticosteroids and immunosuppressive agents) used traditionally in hypersensitivity pneumonitis lack a robust evidence base.

SUMMARY

With a clear definition of fibrotic and nonfibrotic hypersensitivity pneumonitis phenotypes now established, clinical research trials (predominantly randomized controlled trials) should clarify and resolve the discussion regarding antigen avoidance, corticosteroid therapy, immunosuppressive therapy and antifibrotic therapy in fibrotic and nonfibrotic subtypes of hypersensitivity pneumonitis.

Exposure Assessment Tools for Hypersensitivity Pneumonitis. An Official American Thoracic Society Workshop Report

This report is based on proceedings from the Exposure Assessment Tools for Hypersensitivity Pneumonitis (HP) Workshop, sponsored by the American Thoracic Society, that took place on May 18, 2019, in Dallas, Texas. The workshop was initiated by members from the Environmental, Occupational, and Population Health and Clinical Problems Assemblies of the American Thoracic Society. Participants included international experts from pulmonary medicine, occupational medicine, radiology, pathology, and exposure science. The meeting objectives were to 1) define currently available tools for exposure assessment in evaluation of HP, 2) describe the evidence base supporting the role for these exposure assessment tools in HP evaluation, 3) identify limitations and barriers to each tool's implementation in clinical practice, 4) determine which exposure assessment tools demonstrate the best performance characteristics and applicability, and 5) identify research needs for improving exposure assessment tools for HP. Specific discussion topics included history-taking and exposure questionnaires, antigen avoidance, environmental assessment, specific inhalational challenge, serum-specific IgG testing, skin testing, lymphocyte proliferation testing, and a multidisciplinary team approach. Priorities for research in this area were identified.

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.

Diagnosis of Hypersensitivity Pneumonitis in Adults. An Official ATS/JRS/ALAT Clinical Practice Guideline

Background: This guideline addresses the diagnosis of hypersensitivity pneumonitis (HP). It represents a collaborative effort among the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax.Methods: Systematic reviews were performed for six questions. The evidence was discussed, and then recommendations were formulated by a multidisciplinary committee of experts in the field of interstitial lung disease and HP using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach.Results: The guideline committee defined HP, and clinical, radiographic, and pathological features were described. HP was classified into nonfibrotic and fibrotic phenotypes. There was limited evidence that was directly applicable to all questions. The need for a thorough history and a validated questionnaire to identify potential exposures was agreed on. Serum IgG testing against potential antigens associated with HP was suggested to identify potential exposures. For patients with nonfibrotic HP, a recommendation was made in favor of obtaining bronchoalveolar lavage (BAL) fluid for lymphocyte cellular analysis, and suggestions for transbronchial lung biopsy and surgical lung biopsy were also made. For patients with fibrotic HP, suggestions were made in favor of obtaining BAL for lymphocyte cellular analysis, transbronchial lung cryobiopsy, and surgical lung biopsy. Diagnostic criteria were established, and a diagnostic algorithm was created by expert consensus. Knowledge gaps were identified as future research directions.Conclusions: The guideline committee developed a systematic approach to the diagnosis of HP. The approach should be reevaluated as new evidence accumulates.

Fibrotic Hypersensitivity Pneumonitis: Diagnosis and Management

Fibrotic hypersensitivity pneumonitis is a complex interstitial lung disease that is not entirely understood. In its chronic and fibrotic form, hypersensitivity pneumonitis is one of the main mimickers of idiopathic pulmonary fibrosis (IPF). Distinguishing between these two conditions is challenging but is of particular clinical relevance. Two approved therapies are available for IPF, and a considerable number of clinical trials are now exploring newer pharmacological options. This impressive research effort is a consequence of new pathogenetic understanding, updated diagnostic criteria and a long history of pharmacological trials. Conversely, current knowledge gaps on pathogenesis of chronic hypersensitivity pneumonitis, coupled with lack of validated diagnostic criteria, make the management of this disease an unsolved clinical challenge. This also reflects the paucity of therapeutic clinical trials in this field. In this review, we describe the current evidence and the possible future options to approach this complex disease.

Hypersensitivity Pneumonitis and (Idiopathic) Pulmonary Fibrosis Due to Feather Duvets and Pillows

INTRODUCTION

Exposure to feather bedding may be an unnoticed cause of hypersensitivity pneumonitis (HP) and idiopathic pulmonary fibrosis (IPF). Thus, an in-depth clinical study of the diagnosis of patients with suspected HP and IPF is required in order to determine their etiologies. The objective of the present study is to raise awareness of HP and pulmonary fibrosis due to exposure to feather bedding, and to study the prevalence and describe long-term outcomes.

METHODS

We describe a series of 33 patients diagnosed with HP and pulmonary fibrosis due to feather bedding exposure and followed over a 10-year period. The patients were from a subgroup of 127 individuals with HP undergoing in-depth evaluation using a diagnostic protocol at a regional referral center.

RESULTS

Eleven (33%) patients were clinically diagnosed with acute HP and 22 (67%) with chronic HP. Ten (45%) chronic HP patients showed a high resolution computed tomography (HRCT) pattern of usual interstitial pneumonia (UIP) with suspected IPF. The prevalence of HP was 6.2/100 000 feather bedding users (compared with 54.6 per 100 000 bird-breeders). The survival rates of patients over the 10-year period was 100% for acute HP and 64% for chronic HP.

CONCLUSIONS

In a series of HP patients, the diagnosis was attributed to feather bedding exposure in 26%. UIP pattern on HRCT was present in nearly half of the chronic cases. The survival of patients with chronic HP at ten years was 64%, despite avoiding further exposure.

Diagnostic accuracy of specific IgG antibodies for bird fancier's lung: a systematic review and meta-analysis

Background

Serologic assays for specific immunoglobulin G (IgG) antibodies are available for diagnosing the condition of bird fancier's lung, however, their usefulness is controversial. This systematic review was aimed at investigating the diagnostic accuracy of specific IgG antibodies used for avian antigens.

Methods

Medline, Embase, the Cochrane Library, the International Clinical Trials Registry Platform, and the Web of Science were searched for studies performed to evaluate the diagnostic accuracy of the Ouchterlony method, enzyme-linked immunosorbent assays (ELISAs), electrosyneresis, and ImmunoCAP assays for diagnosing bird fancier's lung. Nine articles were included in the meta-analysis. The pooled sensitivity and specificity were summarized using a bivariate mixed-effects model, and a hierarchical summary receiver operating characteristic curve was rendered to determine the diagnostic accuracy of the antibodies.

Results

The pooled sensitivities and specificities of each specific IgG antibody were 82.9% (95% confidence interval, 71.1-90.5%) and 93.0% (95% confidence interval, 74.4-98.4%) for the Ouchterlony method, 92.5% (95% confidence interval, 71.3-98.4%) and 90.8% (95% confidence interval, 72.1-97.4%) for ELISAs, 90.0% (95% confidence interval, 55.5-99.7%) and 84.6% (95% confidence interval, 73.5-92.4%) for the electrosyneresis method, and 43.5% (95% confidence interval, 35.3-52.1%) and 100% (95% confidence interval, 0-100%) for ImmunoCAP assays. The overall quality of the collective evidence was low, primarily due to the high risk of bias, indirectness, and imprecision of the included studies.

Conclusions

The Ouchterlony method demonstrated high specificity, the ELISA method showed high sensitivity, and the diagnostic utilities of electrosyneresis and ImmunoCAP assay testing remain unclear.

Hypersensitivity pneumonitis: Antigen diversity and disease implications

Hypersensitivity pneumonitis (HP) is an immune-mediated syndrome triggered by inhalation of a wide variety of allergens, to which an individual has previously been sensitized. More than 200 agents responsible for the disease have already been identified; however, HP occurs only in a small number of individuals exposed to causal antigens. The present report provides an overview of the role of antigen role in HP, highlighting its diversity, research methods, and prevention strategies, as well as the impact on disease prognosis following elimination of antigen. HP is an underdiagnosed disease and, therefore, it is difficult to accurately estimate its incidence. Triggering antigens can be divided into six broad categories: bacteria, fungi, mycobacteria, animal and plant proteins, chemicals, and metals, represented by disease prototypes. The identification of causal antigen is a major challenge; it is impossible to obtain in about 30-60% of cases. The acute form of HP, with early detection and immediate eviction of causal antigen, tends to have an excellent prognosis. In the chronic form, partial recovery of disease is still possible; however, some cases tend to progress to fibrosis, even after removal from exposure. In conclusion, HP diagnosis should be based on a proactive search for potential antigen sources, although their identification is hampered by the lack of standardized methods of demonstrating the specific antigen sensitization. Antigen avoidance is a critical determinant in disease prognosis.

Identification of Diagnostic Criteria for Chronic Hypersensitivity Pneumonitis: An International Modified Delphi Survey

RATIONALE

Current diagnosis of chronic hypersensitivity pneumonitis (cHP) involves considering a combination of clinical, radiological, and pathological information in multidisciplinary team discussions. However, this approach is highly variable with poor agreement between centers.

OBJECTIVES

We aimed to identify diagnostic criteria for cHP that reach consensus among international experts.

METHODS

A 3-round modified Delphi survey was conducted between April and August 2017. Forty-five experts in interstitial lung disease from 14 countries participated in the online survey. Diagnostic items included in round 1 were generated using expert interviews and literature review. During rounds 1 and 2, experts rated the importance of each diagnostic item on a 5-point Likert scale. The a priori threshold of consensus was ≥ 75% of experts rating a diagnostic item as very important or important. In the third round, experts graded the items that met consensus as important and provided their level of diagnostic confidence for a series of clinical scenarios.

MEASUREMENTS AND MAIN RESULTS

Consensus was achieved on 18 of the 40 diagnostic items. Among these, experts gave the highest level of importance to the identification of a causative antigen, time relation between exposure and disease, mosaic attenuation on chest imaging, and poorly formed non-necrotizing granulomas on pathology. In clinical scenarios, the diagnostic confidence of experts in cHP was heightened by the presence of these diagnostic items.

CONCLUSION

This consensus-based approach for the diagnosis of cHP represents a first step towards the development of international guidelines for the diagnosis of cHP.

Fibrotic Hypersensitivity Pneumonitis: Key Issues in Diagnosis and Management

The diagnosis of hypersensitivity pneumonitis (HP) relies on the clinical evaluation of a number of features, including a history of significant exposure to potentially causative antigens, physical examination, chest CT scan appearances, bronchoalveolar lavage lymphocytosis, and, in selected cases, histology. The presence of fibrosis is associated with higher morbidity and mortality. Differentiating fibrotic HP from the idiopathic interstitial pneumonias can be a challenge. Furthermore, even in the context of a clear diagnosis of fibrotic HP, the disease behaviour can parallel that of idiopathic pulmonary fibrosis in a subgroup, with inexorable progression despite treatment. We review the current knowledge on the diagnosis, management, and prognosis of HP with particular focus on the fibrotic phenotype.

Hypersensitivity pneumonitis: a complex lung disease

Hypersensitivity pneumonitis (HP), also called extrinsic allergic alveolitis, is a respiratory syndrome involving the lung parenchyma and specifically the alveoli, terminal bronchioli, and alveolar interstitium, due to a delayed allergic reaction. Such reaction is secondary to a repeated and prolonged inhalation of different types of organic dusts or other substances to which the patient is sensitized and hyper responsive, primarily consisting of organic dusts of animal or vegetable origin, more rarely from chemicals. The prevalence of HP is difficult to evaluate because of uncertainties in detection and misdiagnosis and lacking of widely accepted diagnostic criteria, and varies considerably depending on disease definition, diagnostic methods, exposure modalities, geographical conditions, agricultural and industrial practices, and host risk factors. HP can be caused by multiple agents that are present in work places and in the home, such as microbes, animal and plant proteins, organic and inorganic chemicals. The number of environment, settings and causative agents is increasing over time. From the clinical point of view HP can be divided in acute/subacute and chronic, depending on the intensity and frequency of exposure to causative antigens. The mainstay in managing HP is the avoidance of the causative antigen, though the complete removal is not always possible due to the difficulties to identify the agent or because its avoidance may lead to major changes in life style or occupational settings. HP is a complex syndrome that needs urgently for more stringent and selective diagnostic criteria and validation, including wider panels of IgG, and a closer collaboration with occupational physicians, as part of a multidisciplinary expertise.

Uncertain areas in the diagnosis of allergic bronchopulmonary aspergillosis in patients with asthma

BACKGROUND AND OBJECTIVE

The prevalence of allergic bronchopulmonary aspergillosis (ABPA) in patients with bronchial asthma remains unknown. We evaluated the roles of various laboratory tests in the diagnosis of ABPA, including, skin prick test (SPT) for Aspergillus fumigatus (Af), and serum Af specific IgE and IgG antibody measurement.

METHODS

A total of 50 asthma patients with more than 1000cell/μL of peripheral blood eosinophils were prospectively collected between January 2007 and September 2011. Evaluations using SPT for Af, serum total IgE and specific IgE antibody to Af by CAP system, IgG antibody to Af by enzyme immunoassay (EIA) or CAP system were performed according to the essential minimal criteria for the diagnosis of ABPA - asthma, immediate cutaneous reactivity to Af, elevated total IgE, and raised Af specific IgE and IgG.

RESULTS

Among 50 patients, three patients (6.0%) were diagnosed as ABPA, of whom each confirmed five items of the essential minimal diagnostic criteria for the diagnosis of ABPA. Six patients (12.0%) showed negative responses to Af in SPT, but positive responses in specific IgE by CAP system. Eight patients (16.0%) showed negative responses to IgG to Af by CAP system, but positive responses by enzyme immunoassay (EIA).

CONCLUSIONS

SPT and serum IgE to Af measurement by CAP system should be performed simultaneously. It is reasonable to set up cut-off values in Af specific IgE/IgG by CAP system for the differentiation of ABPA from Af sensitised asthma patients.

Significance of specific IgG against sensitizing antigens in extrinsic allergic alveolitis: serological methods in EAA

The aim of our study is to find differences in IgG in sera of potentially exposed and nonexposed individuals and to detect differences in concentrations of specific serum IgG among subjects with and without EAA. Seventy-two patients being followed for suspected interstitial lung disease were included. Specific IgG in sera were established by ImmunoCAP. Serum concentrations of Aspergillus fumigatus, Candida albicans IgG and mixture of moulds IgG were higher in subjects with exposure to relevant inhalation antigens (p<0.05). Patients exposed to parrot and mammal hair mixture had higher serum concentration of specific IgG (p<0.05). Subjects without exposure to mites had lower serum IgG to Dermatophagoides pteronyssinus, Dermatophagoides farinae, Dermatophagoides microceras and Glycophagus domesticus (p<0.05). Higher concentration of serum specific IgG may show previous exposure to this antigen. Even though mite specific IgG are not commonly tested in EAA patients, we suggest their immunomodulatory activity may influence susceptibility to other inhalation antigens.

A new application of Streptavidin ImmunoCAP for measuring IgG antibodies against non-available commercial antigens

BACKGROUND

Enzyme immunoassay has been successfully used for the diagnosis of hypersensitivity pneumonitis (HP), but there are difficulties in standardising this method because of the difficulty in obtaining stable solid phases from a huge variety of heterogeneous antigenic sources. With this in mind, the aim of this work was to demonstrate the usefulness of the standard available fluoro-enzyme-immuno-assay (FEIA) to measure specific IgG to uncommon, commercially unavailable HP-causing antigens.

METHODS

Serum samples from patients suffering from HP caused by canary and pigeon protein exposure with positive immunoprecipitation values, as well as cystic fibrosis patients, patients with respiratory allergies, asymptomatic subjects exposed to canary proteins (canary breeders) and healthy unexposed individuals were evaluated by FEIA using biotinylated serum proteins coupled to streptavidin-activated solid phases. Statistical analyses were performed to compare the different groups and to evaluate the performance of this technique.

RESULTS

The group of patients with hypersensitivity pneumonitis caused by exposure to canary proteins showed the highest value of specific IgG (35.70 mg IgG/mL). ROC analysis demonstrated an optimal cut-off value of 8.44 mg IgG/mL with a sensitivity of 100% and a specificity of 91.76%. Comparisons with other groups revealed statistically significant differences. Comparison between ELISA and FEIA results revealed a strong positive relationship between values obtained in both assays.

CONCLUSION

The results demonstrate that Streptavidin ImmunoCAP is a sensitive, specific and efficient laboratory method for routine diagnostic testing of HP caused by protein antigens that are not commercially available.

Bird fancier's lung: a series of 86 patients

Bird fancier's lung (BFL) is one of the most common types of hypersensitivity pneumonitis. Nevertheless, the criteria for diagnosing this condition are not standardized. The current study is an in-depth investigation into the clinical characteristics of BFL in the largest series examined for this purpose by a single group, to our knowledge, taking into account the acute, subacute, or chronic clinical presentation. From 1977 to 2003, BFL was diagnosed in 86 patients using a homogeneous protocol. Data from the clinical history and physical examination were analyzed, as well as the results from the following complementary examinations: laboratory analyses, specific serum IgG antibodies determination, chest X-ray, chest computed tomography (CT), pulmonary function testing, immediate hypersensitivity skin testing, delayed cutaneous hypersensitivity testing, bronchofibroscopy with bronchoalveolar lavage (BAL) and/or transbronchial biopsy, bronchial challenge testing, and surgical lung biopsy. In addition, clinical and epidemiologic characteristics were determined in a control group of 60 pigeon breeders who did not meet the diagnostic criteria of BFL. Eighty-six patients (21 men and 65 women) with a mean age of 47 years were studied. Seven (8%) patients were younger than 15 years of age at the time of the diagnosis. In 3 cases, the disease was caused by exposure to feather-filled bedding. Nearly 1 in 5 patients was diagnosed in the chronic phase of the disease. The mean diagnostic delay was 1.6 years overall, and 3.2 years in patients diagnosed in the chronic phase of the disease. Among the 17% of patients with chronic disease, the mean interval from initiation of exposure to diagnosis was 16 years, a higher value than in the acute or subacute presentation forms. Dyspnea and cough were the most common clinical symptoms (98% and 82%, respectively), and nearly 25% had grade III or IV dyspnea at diagnosis. Only 18% of patients experienced chest tightness, a symptom classically considered to be frequent in this condition. Erythrocyte sedimentation rate was elevated (>30 mm/h) in 44% of patients. Urinary calcium was elevated in 20% of patients. Angiotensin-converting enzyme was not elevated in any of the patients in which it was measured. Lactate dehydrogenase increases were found in 51% of patients. Specific IgG antibodies to avian antigens were documented in 92% of BFL patients, but also in 87% of pigeon breeder controls. The most frequent radiologic finding was an interstitial pattern in 79% of patients. Common chest CT features were ground glass areas (68%) and a mosaic pattern (61%); areas of emphysema were found in 7/41 (17%) patients, 5 of whom had never smoked. Two patients had a CT pattern of pulmonary fibrosis indistinguishable from idiopathic pulmonary fibrosis. Immediate hypersensitivity skin testing with bird sera and pigeon bloom was positive in 78% and 100% of BFL patients, respectively, and in 64% and 88% of control pigeon breeders, respectively. Almost one-third of the patients (29%) presented an anergic response on delayed cutaneous hypersensitivity testing. Restrictive ventilatory impairment was the most frequent functional pattern (77%), although 9% and 4% showed a pure obstructive and mixed pattern, respectively. The carbon monoxide diffusing capacity was decreased (<80% of the predicted value) in 85% of cases. Forty-one percent of patients had PaO2 <60 mm Hg at diagnosis when blood gas analysis was performed. Lymphocytosis (>20% lymphocytes) was documented in 83% of patients who underwent BAL, with a similar frequency in the 3 presentation forms: 70% acute, 89% subacute, and 85% chronic. In addition, inversion of the CD4/CD8 ratio (<1) was observed in 62% of the patients, but 38% of cases showed a CD4 predominance. The characteristic triad of histopathologic findings in hypersensitivity pneumonitis was found in only 9% of patients undergoing transbronchial biopsy, but at least 1 of these findings was seen in 69%. Surgical lung biopsy was undertaken in 14/86 (16%) patients; the complete triad was observed in 50% and at least 1 finding in 100%. In 54/86 (63%) patients, the diagnosis was confirmed by bronchial challenge testing, a test with a sensitivity of 92% and specificity of 100%. BFL is a potentially severe disease that can progress to respiratory failure secondary to pulmonary fibrosis or chronic obstructive pulmonary disease, as a form of chronic occupational respiratory disease. Respiratory symptoms in exposed patients, including children and adults who have only 1 pet bird at home, should raise the suspicion of BFL. Diagnosis in the chronic phase is frequent, and the delay to diagnosis was greatest in these cases. Elevated urinary calcium, lactate dehydrogenase, and erythrocyte sedimentation rate in a bird fancier may constitute a combined marker for suspected BFL. Chest CT frequently discloses emphysema and a pattern of idiopathic pulmonary fibrosis in some patients. An anergic response on delayed cutaneous hypersensitivity testing is not infrequent. The presentation with respiratory failure and the predominance of CD4 T lymphocytes in some patients' BAL are both remarkable. Lymphocytosis on BAL also persists in the chronic phase of the disease. Bronchial challenge testing has a high diagnostic yield, and surgical lung biopsy is not needed to reach the final diagnosis in the vast majority of cases.

Hypersensitivity pneumonitis: clinical perspectives

CONTEXT

The clinical course of hypersensitivity pneumonitis (HSP) is highly variable and its diagnosis clinically challenging.

OBJECTIVE

To provide a concise review of major clinical, radiographic, and laboratory findings that permits diagnosis of HSP from the standpoint of a clinician/pulmonologist.

DATA SOURCES

Review of major contemporary and historical literature in combination with the author's experience and viewpoints.

CONCLUSIONS

The approach to the diagnosis of HSP is multidisciplinary. For patients being evaluated for unexplained dyspnea and cough and an unknown interstitial disease process, the initial evaluation should include detailed environmental and occupational histories with ancillary testing such as serology, chest imaging, inhalation challenges, and bronchoalveolar lavage, as indicated. In uncertain cases, lung biopsy is recommended.

Progressive dyspnea in a 46-year-old woman

BACKGROUND

Hypersensitivity pneumonitis (HP) is an inflammatory lung disease that requires a high index of suspicion and evaluation for potential causative antigens in the patient's environment.

OBJECTIVE

To describe a patient referred for allergic rhinitis who was found to have progressive dyspnea and was ultimately diagnosed as having HP.

METHODS

The history of progressive dyspnea with findings of diffuse pulmonary crackles on physical examination and restrictive pulmonary function testing prompted further radiologic, pathologic, laboratory, and home environment evaluations.

RESULTS

The constellation of findings from these studies led to the diagnosis of HP secondary to parakeet antigens. Elimination of further antigen exposure and corticosteroid therapy led to resolution of the patient's symptoms.

CONCLUSION

Prompt diagnosis and removal of the antigen source are of paramount importance in the management of HP.

Avian circoviruses of the genus Circovirus: A potential trigger in Pigeon breeder’s lung (PBL)/Bird fancier’s lung (BFL)

Pigeon breeder's lung (PBL) or Bird fancier's lung (BFL) is one of the most common extrinsic allergic alveolitis or hypersensitivity pneumonitis. It is caused after prolonged inhalation of avian antigens and provokes a hypersensitivity reaction in the lungs of sensitised people. Although the pathogenic mechanism is unclear, the epidemiology of BFL shows that it occurs worldwide, and has been described in adults keeping birds and also in their children. Laboratory findings associated with the disease classified as a type III immunologic reaction that produces blood precipitin antibodies against birds' serum, feathers, intestinal mucin and/or faeces. In particular, the fine dust from pigeon feathers has strong antigenic properties. There is an interaction between host and antigen that seems to be influenced by both genetic and environmental factors. Avian circoviruses (ACV) of the genus Circovirus, has been detected in free-ranging and captive birds worldwide, such as pigeons, canaries, psittacines, Senegal doves, finches, gulls, Australian ravens and geese. T lymphocytes are the main target cells of the ACV and in the above avian species circovirus-like particles were detected in blood, macrophages, feathers, crop secretions, intestinal contents and/or faeces. Most of the ACV was demonstrated that are pantropic and viral antigen in pigeon tissues was most commonly detected in respiratory organs, including the trachea, pharynx and lung. The transmission of the circovirus between the birds usually occurs through inhalation of feathers dust. There is evidence that animal circoviruses may originate when vertebrates become "infected" with DNA from a plant nanovirus. So, it seems that further investigation for the avian circoviruses is needed to determine if they are host specific or not. This study attempts to demonstrate ACV or ACV-like particles as potential triggers in the BFL aetiology, and the possible involvement in BFL's pathogenic mechanism.

Quantification of IgG antibodies to Aspergillus fumigatus and pigeon antigens by ImmunoCAP technology: an alternative to the precipitation technique?

BACKGROUND

We evaluated the ImmunoCAP technique for measurement of IgG specific to Aspergillus fumigatus and pigeon antigens.

METHODS

We used ImmunoCAP and precipitation technique to measure concentrations of IgG to A. fumigatus or pigeon antigens in sera from 265 patients and 42 controls. We also evaluated linearity, interference, imprecision, concordance, and diagnostic accuracy of the measuring techniques.

RESULTS

The precipitation and ImmunoCAP technique showed moderate concordance (kappa, 0.46 for both A. fumigatus and pigeon antibodies). Specific IgG results for A. fumigatus and pigeon were linear (r = 0.98 and 0.97, respectively), with interrun reproducibility rates of 23% and 14% and maximal interference of 36.5% and 8% by lipid and 24% and 21% by hemolysis, respectively. A. fumigatus antibody concentrations were higher in patients with aspergillosis and allergic bronchopulmonary aspergillosis (ABPA) (median, 103 and 70.1 mgA/L, respectively) than in patients with other pulmonary diseases (median, 18.15-33.40 mgA/L). Antibodies to pigeon antigens were high in patients with hypersensitivity pneumonitis (median, 1024 mgA/L) but also in patients with other pulmonary diseases (median, 445 mgA/L). Antibody titers were substantially higher in patients with other pulmonary diseases and contact with pigeons (median, 1060 mgA/L) than in patients without antigen contact (median, 27.35 mgA/L) (P <0.004).

CONCLUSIONS

Agreement between the precipitation and ImmunoCAP technique was 86% for A. fumigatus and 70% for pigeon antigens. Highest concentrations of specific IgG to A. fumigatus were found in patients with aspergillosis and ABPA. Our results suggest that antigen contact was the most important variable affecting the presence of antibodies to pigeon antigen.

Hypersensitivity pneumonitis in children: clinical features, diagnosis, and treatment

Hypersensitivity pneumonitis (HP), or extrinsic allergic alveolitis, is a form of immune-mediated inflammatory lung disease involving the distal portions of the lungs associated with intense or repeated exposure to a variety of finely dispersed environmental antigens. Although once believed to be a disease of adults because of its frequent association with the occupational setting, HP exists in the pediatric population and often goes unrecognized. Childhood HP is often associated with exposure to antigens in the home environment as well as with certain hobbies. Patients present in any one of the three disease stages: acute, subacute, and chronic, all with unique clinical presentations. Histopathologic findings depend on the disease stage at the time of evaluation. The immuno-pathogenesis is complex, but immune-complex (type III hypersensitivity) and cell-mediated (type IV hypersensitivity) immune responses appear to be the primary immune mechanisms involved in the pathogenesis of HP. Diagnosis can be very challenging. Although no single diagnostic or clinical laboratory test is available to diagnose HP, the most significant diagnostic tool is a detailed environmental exposure history. Avoidance of the inciting antigen is the most important form of treatment. Acute HP is responsive to antigen removal alone. However, a short course of prednisone for 2-3 weeks can be useful in patients with severe attacks. Subacute and chronic HP may require higher doses of corticosteroids for a longer duration (i.e. months); however, the long-term efficacy of using corticosteroids is still not well defined. As with most hypersensitivity diseases, early diagnosis provides the best prognosis.

Use of co-immunoelectrodiffusion to detect presumed disease-associated precipitating antibodies, and time-course value of specific isotypes in bird-breeder's disease

BACKGROUND AND OBJECTIVE

The practical value of immunological diagnosis of bird-breeder's disease (BBD) is controversial, because of difficulties in distinguishing active disease patients from simple contact subjects. The aim of this study was to determine the diagnostic and prognostic value of (a) presumed disease-associated antibodies precipitating pigeon antigens (immunoglobulin A (IgAp) and P2 component), (b) characterization of specific isotypes (IgG, IgM, and IgA), and (c) antibody kinetics after antigen eradication.

METHODS

405 subjects (775 sera) in contact with birds were studied [by means of co-immunoelectrodiffusion (Co-IED) and enzyme-linked immunofiltration (ELIFA)] with soluble extracts of pigeon droppings and squab crop milk. These patients were divided into two groups based on the final clinical evaluation of the patients' physicians, which was taken as the gold standard (positive in 90 and negative in 315 cases).

RESULTS

On the basis of this gold standard, the detection of presumed disease-associated precipitating antibodies by Co-IED had a specificity of 95.5%, a sensitivity of 98.7%, an accuracy of 98%, and positive and negative predictive values of 95.5% and 98.7%, respectively. Most of the patients with a final positive diagnosis of BBD had specific IgG, IgM, and IgA antibodies by ELIFA. After antigen eradication, anti IgAp and/or P2 antibodies disappeared more rapidly than other precipitating systems.

CONCLUSION

Identification by Co-IED of precipitating immune complexes IgAp and/or P2 significantly reinforces the intrinsic credibility of immunological diagnosis of BBD. Compared to these presumed disease-associated precipitating antibodies, detection and time course of specific IgM, IgA antibodies, provided no additional diagnostic value or prognostic arguments to judge disease activity after antigen eradication.

Cockatiel-induced hypersensitivity pneumonitis

Diagnosing an environmental or occupationally related pulmonary disorder often involves a process of elimination. Unlike commonly diagnosed conditions in other specialties, a cause-and-effect relationship may be implied, yet other factors such as temporality and biologic plausibility are lacking. Our patient was referred with a suspected work-related pulmonary disorder. For several years, she had suffered with dyspnea on exertion and repeated flulike illnesses. She worked at an automobile repair garage that performed a large number of emission tests, and there was concern that her workplace exposures were the cause of her symptoms. After a careful review of her history, physical examination, and laboratory testing, we came to the conclusion that she had hypersensitivity pneumonitis related to pet cockatiels in her home. Clinical points of emphasis include the importance of a complete environmental history and careful auscultation of the chest when performing the physical examination. In addition, we encountered an interesting physical diagnostic clue, a respiratory sound that assisted with the eventual diagnosis.

Hypersensitivity pneumonitis: current concepts and future questions

Hypersensitivity pneumonitis (extrinsic allergic alveolitis) caused by inhaled allergens can progress to disabling or even fatal end-stage lung disease. The only truly effective treatment is early recognition and control of exposure. Although patients produce antibody exuberantly, the immunopathogenesis involves cellular immunity--notably, CD8(+) cytotoxic lymphocytes, multinucleate giant cell granulomas, and ultimately interstitial fibrosis. Many causative agents have been recognized in occupational dusts or mists, but most current new cases arise from residential exposure to pet birds (pigeons and parakeets), contaminated humidifiers, and indoor molds. The symptoms and physical findings are nonspecific. Serum IgG containing high titers of specific antibody to the offending antigen is elevated. Pulmonary function tests show restrictive and diffusion defects with hypoxemia, especially after exercise. Occasionally, small airways disease causes obstruction. Radio-graphic changes vary according to the stage of the disease and are best evaluated by means of high-resolution computed tomography. In typical cases, the history of a known exposure and the presence of a characteristic interstitial lung disease with serologic confirmation of IgG antibody to the offending antigen suffice for diagnosis. In more obscure cases, observation of changes after a natural environmental exposure, bronchoalveolar lavage, and lung biopsy might be indicated. Among the many questions that remain are the following: What is the prevalence of hypersensitivity pneumonitis and how often is it the cause of chronic interstitial fibrosis? What is the long-term prognosis? Why do most individuals exposed to these antigens develop a vigorous antibody response whereas only a few develop the disease? How does exposure to endotoxin and cigarette smoking affect the disease? To answer these questions, standardized and validated clinical laboratory immunochemical tests are needed, in addition to a systematic approach to diagnosis, classification of disease severity, risk assessment, and management. This review is limited to the disease caused by airborne allergens and focuses on its immunopathogenesis, eliciting agents, clinical manifestations, diagnosis, management, and prognosis.