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Hypersensitivity pneumonitis

Key sources
The following summarized guidelines for the evaluation and management of hypersensitivity pneumonitis are prepared by our editorial team based on guidelines from the American College of Chest Physicians (ACCP 2021), the Latin American Thoracic Association (ALAT/JRS/ATS 2020), the American Thoracic Society (ATS 2011), and the British Thoracic Society (BTS/TSANZ/ITS 2008).


1.Screening and diagnosis

Diagnosis: as per ACCP 2021 guidelines, consider using clinical improvement with antigen avoidance, if an inciting antigen is identified and then completely avoided, to support the diagnosis in patients with suspected HP. Avoid relying solely on the lack of clinical improvement with antigen avoidance to rule out the diagnosis of HP.
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2.Classification and risk stratification

Consider classifying patients with suspected HP based on the likelihood of an occupational or environmental inciting antigen exposure.
Consider classifying the disease as fibrotic or non-fibrotic based on the presence or absence of fibrosis on HRCT of the chest in patients with either newly diagnosed or a working diagnosis of HP.

3.Diagnostic investigations

General principles
Consider using a multidisciplinary discussion for diagnostic decision-making in patients with suspected HP.
Consider including an occupational medicine specialist and an environmental hygienist in the multidisciplinary diagnostic workup in patients with suspected HP, if the inciting antigen is thought to be related to an occupational exposure especially if the source of exposure is obscure or unverified.

More topics in this section

  • Exposure history

  • Antigen-specific antibodies

  • Antigen-specific lymphocyte proliferation testing

  • CT

4.Diagnostic procedures

Bronchoalveolar lavage: as per ACCP 2021 guidelines, do not perform routine BAL fluid analysis to confirm the diagnosis in patients with suspected HP having a compelling exposure history within the appropriate clinical context and a chest HRCT pattern typical for HP.

More topics in this section

  • Inhalation challenge testing

  • Lung biopsy

5.Medical management

Corticosteroids: consider offering corticosteroids for the management of patients with severe or progressive HP.

6.Nonpharmacologic interventions

Avoidance of causative antigens: offer avoiding of the causative antigens, when identified, as the most important and effective aspect of management.

7.Specific circumstances

Patients with hypersensitivity pneumonitis related to Aspergillus
Advise avoidance of Aspergillus exposure in patients with HP related to Aspergillus and, when necessary, initiate corticosteroid therapy up to 60 mg/day, tapering over 1 month.
Do not use antifungal therapy in patients with HP related to Aspergillus.