Current and emerging techniques for the diagnosis of hypersensitivity pneumonitis

Transbronchial Lung Cryobiopsy in Patients with Interstitial Lung Disease: A Systematic Review

RATIONALE

In 2018, a systematic review evaluating transbronchial lung cryobiopsy (TBLC) in patients with interstitial lung disease (ILD) was performed to inform American Thoracic Society (ATS), European Respiratory Society (ERS), Japanese Respiratory Society (JRS), and Asociación Latinoamericana del Tórax (ALAT) clinical practice guidelines on the diagnosis of idiopathic pulmonary fibrosis (IPF).

OBJECTIVE

To perform a new systematic review to inform updated guidelines.

METHODS

Medline, EMBASE and the Cochrane Central Register of Controlled Trials (CCTR) were searched through June 2020. Studies that enrolled patients with ILD and reported the diagnostic yield or complication rates of TBLC were selected for inclusion. Data was extracted and then pooled across studies via meta-analysis. The quality of the evidence was appraised using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Histopathologic diagnostic yield (number of procedures that yielded a histopathologic diagnosis divided by the total number of procedures performed) of TBLC was 80% (95% CI 76-83%) in patients with ILD. TBLC was complicated by bleeding and pneumothorax in 30% (95% CI 20-41%) and 8% (95% CI 6-11%) of patients, respectively. Procedure-related mortality, severe bleeding, prolonged air leak, acute exacerbation, respiratory failure, and respiratory infection were rare. The quality of the evidence was very low due to the uncontrolled study designs, lack of consecutive enrollment, and inconsistent results.

CONCLUSION

Very low-quality evidence indicated that TBLC has a diagnostic yield of approximately 80% in patients with ILD, with manageable complications.

[Hot tub lung: A retrospective analysis of 14 cases]

INTRODUCTION

Hot tub lung (HTL) is a hypersensitivity pneumonitis (HP) related to inhalation of non-tuberculous mycobacteria (NTM) when exposed to ejected jet droplets from a jacuzzi. The aetiological debate is not completely settled in the literature.

METHOD

An observational study of 14 cases of HTL, diagnosed at the University Hospital of Besançon, France, between 2004 and 2018 according to the diagnostic criteria used in the clinic.

RESULTS

This cohort corresponds to type I HP (inflammatory), with one case of type II HP. Decrease of lung transfer for carbon monoxide was present in 86% of examinations (n=12/14). In total, 84% of bronchoalveolar lavages showed a lymphocytic cellular pattern≥30% (n=11/13). The environmental survey enabled the identification of NTM in 93% of cases (n=13/14), mainly Mycobacterium avium. Serum precipitins directed against NTM were found in 10% of the cases (n=2/20). Three cases received corticosteroid therapy and none received antibiotics. Antigenic eviction has improved the symptomatology in all cases.

CONCLUSIONS

Our cohort supports the hypothesis that HTL is predominantly a type I HP. Avoidance of the agent involved (NTM) is necessary. The diagnosis is difficult because serum precipitins against NTM are not easily demonstrable. An environmental survey could facilitate the identification of the NTM. Prevention of HTL depends on education of the clinician and the patient.

Krebs von den Lungen-6 (KL-6) is a pathophysiological biomarker of early-stage acute hypersensitivity pneumonitis among pigeon fanciers

BACKGROUND

Identifying early stages of hypersensitivity pneumonitis (HP) is hampered by variable presentation, heterogeneous or undetected causal antigens and lack of gold-standard biomarkers. Krebs von den Lungen (KL)-6 is pathophysiological biomarker of alveolar epithelial damage. Pigeon fanciers, susceptible to HP, provide a model to investigate early HP.

OBJECTIVE

To test the hypothesis that plasma concentrations of KL-6 are increased in early-stage acute HP.

METHODS

Clinical history, spirometry and blood samples were obtained from pigeon fanciers, 20 with intermittent acute symptoms indicative of developing HP, 27 with no symptoms and 10 healthy subjects with no avian exposure. Plasma KL-6 (units/mL) and pigeon antigen-specific IgG antibody were quantified by enzyme immunoassay. Blood lymphocytes were quantified by flow cytometry and antigen specificity by in vitro cytokine production.

RESULTS

KL-6 was higher in fanciers than controls, median (IQR) 452 (244, 632) vs 274 (151, 377), P = .01. Although fanciers with symptoms had similar antigen exposure and lung function, they had higher KL-6 than those without, 632 (468, 1314) vs 320 (200, 480), P < .001. KL-6 correlated with IgG antibody titre in those with symptoms, r = .591, P = .006. High KL-6, irrespective of symptom category, was associated with higher antibody (P = .006) and lymphocyte proliferation (P = .041), and lower CD4+ T lymphocyte proportion (P = .032).

CONCLUSION AND CLINICAL RELEVANCE

Raised KL-6 is associated with acute symptoms of early-stage HP, and its correlation with antibody may support therapeutic strategies when HP is suspected. KL-6 may act as a mechanistic biomarker of early pathogenesis by linking lung pathophysiological changes with an endotype of immune hypersensitivity.

[Adenopathy and mammary carcinoma: It is sometimes in the details that one encounters hypersensitivity pneumonitis!]

INTRODUCTION

Hypersensitivity pneumonitis (HP) is an interstitial lung disease due to an immunological reaction to exposure, by inhalation, to a large variety of antigens. The patho-physiological mechanism remains poorly understood. The diagnosis can be challenging and requires a detailed medical history taking especially when the clinical presentation is atypical or when the causal agent remains unknown.

CASE REPORT

We report the case of a 75-year-old woman with a history of mammary carcinoma who presented with recently identified intramammary adenopathy. Biopsy of the adenopathy revealed non-necrotising, giant cell epithelioid granuloma. A diagnosis of hot tub lung with extra-pulmonary granulomatous lymph node involvement was made based on the clinical, functional, radiological and microbiological investigations. The evolution was favorable following antigen avoidance.

CONCLUSION

Extrapulmonary lymph node involvement is rare in HP, suggesting a systemic inflammatory involvement.

Bronchoalveolar lavage: role in the evaluation of pulmonary interstitial disease

INTRODUCTION

Bronchoalveolar lavage (BAL), a noninvasive, well-tolerated procedure is an important diagnostic tool that can facilitate the diagnosis of various lung diseases. This procedure allows the assessment of large alveolar compartments, by providing cells as well as non-cellular constituents from the lower respiratory tract. Alterations in BAL fluid and cells ratio reflects pathological changes in the lung parenchyma. In some cases, clinicians use BAL as a differential diagnosis guide for interstitial lung disease.

AREAS COVERED

In this review, we summarized the diagnostic criteria for BAL in interstitial lung diseases, pulmonary infections, lung cancer and other pathologies such as fat embolism, gastroesophageal reflux and collagen vascular disease. For this review, we have selected scientific papers published in the PubMed database in our area of interest. We aimed to highlight the usefulness of BAL in respiratory pathology.

EXPERT OPINION

Although BAL fluid analyzes has an essential role in the diagnostic work-up of many lung pathologies, it should be performed in selected patients. For accurate results, the BAL technique is very important to be standardized.

Diagnosis of occupational hypersensitivity pneumonitis

PURPOSE OF REVIEW

To discuss the diagnostic methods currently used in the study of patients with hypersensitivity pneumonitis, with special emphasis on the most recent contributions published in the medical literature regarding the diagnosis of occupational hypersensitivity pneumonitis (OHP). This review presents an update of the use of these diagnostic tests, a controversial issue among experts.

RECENT FINDINGS

In spite of the multiple attempts at systematization and the publication of expert consensus statements, standardizing and diagnostic methods and criteria remain particularly difficult. As a result, centers tend to rely on their own experience and establish diagnosis by consensus among their multidisciplinary teams. Though recommendable in many ways, this method presents significant limitations.

SUMMARY

Diagnosis of OHP should be made with a thorough clinical history of the symptoms and clinical signs as well as a meticulous review, if possible by an expert, of possible exposures in the working environment; a meticulous physical examination; high-resolution computed tomography of the thorax; serum determination of specific immunoglobuline Gs; bronchoalveolar lavage and possibly cryobiopsy; fungal culture; and, when appropriate, a specific inhalation challenge test with the suspected antigen.

Current Diagnosis and Management of Hypersensitivity Pneumonitis

Hypersensitivity Pneumonitis (HP) one of the most common interstitial lung diseases (ILDs) is characterized by exposure to an inhaled inciting antigen that leads to a host immunologic reaction determining interstitial inflammation and architectural distortion. The underlying pathogenetic mechanisms are unclear. The absence of international shared diagnostic guidelines and the lack of a "gold-standard" test for HP combined with the presence of several clinical and radiologic overlapping features makes it particularly challenging to differentiate HP from other ILDs, also in expert contests. Radiology is playing a more crucial role in this process; recently the headcheese sign was recognized as a more specific for chronic-HP than the extensive mosaic attenuation. Several classification proposals and diagnostic models have been advanced by different groups, with no prospective validation. Therapeutic options for HP have been limited to antigen avoidance and immunosuppressant drugs over the last decades. Several questions about this condition remain unanswered and there is a need for more studies.

[A case of farmer's lung associated with allergic bronchopulmonary aspergillosis]

Hypersensitivity pneumonitis and allergic bronchopulmonary aspergillosis are two forms of lung disease with presumed distinct immunoallergic mechanisms. We report the observation of a 38-year-old French farmer who, for one month, had fever and dyspnoea resistant to antibiotic therapy. A diagnosis of farmer's lung, and allergic bronchopulmonary aspergillosis was made on clinical, biological, functional and radiological evidence and according to the criteria established. The evolution was favorable with antigenic eviction and corticosteroid therapy. This observation is to our knowledge the 5^th case that describes the association of hypersensitivity pneumonitis and allergic bronchopulmonary aspergillosis. It suggests the existence of risk factors and immunoallergic mechanisms common to both diseases and discusses the hypothesis that the same antigen(s) is (are) responsible for them.

Hypersensitivity pneumonitis of a bagpipe player: Fungal antigens as trigger?

Here we present a 79-year old man with chronic hypersensitivity pneumonitis probably caused by fungal contamination of a bagpipe. Several samples were taken from the patient's bagpipe. Four potential fungal antigens (Exophiala phaeomuriformis, Kwoniella europaea, Pyrenochaeta unguis-hominis and Aureobasidium melanogenum) as potential trigger of hypersensitivity pneumonitis were identified. A serum ELISA test with Exophiala phaeomuriformis indicated reactivity. Cessation of playing the bagpipe and application of glucocorticoids lead to an improvement of the patient's symptoms.

Hypersensitivity pneumonitis: A new strategy for serodiagnosis and environmental surveys

We propose a strategy for serodiagnosis of hypersensitivity pneumonitis (HP): 1) question patients about their private or occupational activity, or visit him on site; 2) select panels of six somatic specific antigens appropriate for each type of exposure; 3) and use ELISA to test concomitantly two recombinant antigens highly specific to Farmer's lung, Metalworking-fluid HP, and for Bird fancier's lung. The serodiagnosis provides an immunological argument that may complete radiological, functional lung exploration and clinical features; 4) If the serodiagnosis is negative but the suspicion of HP is strong, a microbial analysis of the patient's specific exposure is conducted; 5) "A la carte" antigens are produced from the microorganisms isolated in the patient's environment sample and tested; 6) Finally, the patient may be asked to undergo a specific inhalation challenge with the offending antigens in a safety cabin, or to avoid his usual environment for a few days.