Comparison of immunodiffusion and enzyme linked immunosorbent assay in the detection of abnormal antibodies in pigeon breeder's disease

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.

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.

The value of serum precipitins against specific antigens in patients diagnosed with hypersensitivity pneumonitis - retrospective study

INTRODUCTION

Hypersensitivity pneumonitis (HP) is the third most common interstitial lung disease, and is often under-recognized, especially in patients who are not aware of their occupational or environmental contact with organic antigens. The aim of the present study was to assess the results of serum specific IgG antibodies (ssIgG) in HP patients and their correlation with clinical data.

MATERIAL AND METHODS

128 HP patients, median age 53 years, participated in the study. The control group consisted of 102 patients with interstitial lung diseases (ILDs) other than HP. Assessment of pretreatment ssIgG to thermophilic actinomycetes and protein antigens from bird droppings (pigeons, hens, ducks, parrots, turkeys) was performed by double diffusion in agar gel according to Ouchterlony method.

RESULTS

Positive precipitins were obtained in 57% of all HP patients and in 61% of those exposed to above mentioned antigens. Positive results in the control group were obtained in 7% of patients. Sensitivity of ssIgG in HP group was 0.57 and specificity 0.93. Precipitins to at least one bird antigen was confirmed in 64% of HP patients exposed to birds. Precipitins to thermophilic bacteria were found in 29% of HP patients exposed to hay or hay products.

CONCLUSIONS

The results of the study indicate that ssIgG against birds' allergens were the valuable diagnostic tool in HP patients. Low-rate of confirmation of ssIgG to thermophilic bacteria in patients exposed to hay or hay products indicate that other microorganisms, most likely molds, could be responsible for the disease development.

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.

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.

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.

Anti-avian antibodies and rheumatoid factor in pigeon hypersensitivity pneumonitis

BACKGROUND

Although several immunological abnormalities may be present in pigeon hypersensitivity pneumonitis (HP), few specific hallmarks have been described.

OBJECTIVE

To determine whether the presence of rheumatoid factor (RF) could be useful to discriminate pigeon HP from asymptomatic breeders (AB) and other interstitial lung diseases.

METHODS

Fifty-three patients with pigeon HP, 47 AB, 31 idiopathic pulmonary fibrosis (IPF) patients and a rheumatoid arthritis (RA) group were studied. IgM RF was determined through enzyme-linked immunosorbent assay (ELISA) and western blot using human IgG and IgG Fc fragment as antigens. IgG and IgA anti-avian antibodies (AA) against pigeon serum antigen were also measured. The use of F(ab')2 fraction of peroxidase-labelled anti-human immunoglobulins prevented endogenous interferences. Possible cross-binding of RF with avian antigens and the reactivity against human IgG by AA were studied.

RESULTS

RF tests were frequently positive in HP (52.8%) in comparison to AB (4.2%) and IPF (12.9%; P = 2.6 x 10-10 and 4.1 x 10-5). Therefore, the presence of RF in pigeon HP showed a sensitivity of 52% and was highly specific considering the results of AB and IPF (95 and 87%, respectively). The RA group revealed positive RF but negative AA tests. RF activity was confirmed through western blot using purified IgG Fc fragment. Overlapping levels of IgG and IgA AA were found in HP and AB. The frequency of AA was low in IPF. The cross-reaction of RF with avian antigens was excluded, and no reactivity against human IgG by AA was detected. Other endogenous interferences were ruled out.

CONCLUSION

No single immunological test may definitively distinguish pigeon HP from AB and other interstitial lung disorders; however, positive RF, together with high AA levels, seems to be useful in differentiating the diagnosis.

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.

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

BACKGROUND

Pigeon breeder's disease is an extrinsic allergic alveolitis in the lungs of sensitised people, caused by hypersensitivity reactions to inhaled pigeon antigens. Antigens from different sources of the animal are used for diagnostic purposes, with serum being the most widely used. Bloom is rarely used; very little is known of its antigenicity and diagnostic performance, particularly when used with the enzyme linked immunosorbent assay (ELISA) method, which is the most popular test as it permits measurement of the antibody response.

METHODS

To (a) standardise an ELISA for the measurement of specific IgG against pigeon serum and pigeon bloom extract; (b) to establish reference values for specific IgG in 73 non-exposed controls, (c) to show the presence of specific IgG against pigeon serum and bloom in serum samples of 17 patients with bird fancier's lung and 11 asymptomatic fanciers, and (d) to study the similarity of the two antigen sources by cross reactivity experiments.

RESULTS

Reference values of specific IgG were defined with the 97.5 percentile (367.9 U/ml for pigeon serum and 953.7 U/ml for pigeon bloom extract). Of symptomatic patients 100% had values higher than the cut off for both antigens. In asymptomatic fanciers values were higher than the cut off for pigeon serum in 45% and bloom extract in 54%. Cross reactivity experiments showed that the two antigens differed in antigenic content although some components may be common to both.

CONCLUSION

The ELISA methods used proved to be useful tools for evaluating specific IgG antibody responses against both antigens. The diagnostic performance of both ELISA methods performed with these antigen sources was similar, showing very high sensitivity but moderate specificity. Although some antigenic similarity was found between pigeon serum and bloom extract, cross reactivity studies showed that various antigens seemed to be specific to the bloom extract. However, the antigens responsible for pigeon breeder's disease seem to be present in both antigenic sources.

Shortness of breath secondary to a pet cockatiel

A case of hypersensitivity pneumonitis in a 40-year-old patient secondary to a pet bird is presented. The clinical presentation, diagnosis, and management of hypersensitivity pneumonitis are reviewed.