Criteria

American Thoracic Society, Japanese Respiratory Society, and Latin American Thoracic Association criteria[3]

  • Compatible imaging pattern (lung infiltration, i.e., ground-glass opacity, mosaic attenuation, plus at least one high-resolution computed tomography chest abnormality suggestive of small airway disease)

  • Exposure to known causes of HP (e.g., history of exposure or serum IgG testing)

  • Bronchoalveolar lavage lymphocytosis/histopathologic findings compatible with HP.

Terho diagnostic criteria[44]

Major criteria:

  • Exposure to known causes of HP

  • Compatible history of dyspnea, cough, and malaise

  • Infiltrates on chest x-ray.

Minor criteria:

  • Rales on exam

  • Abnormal pulmonary function tests; restrictive pattern

  • Decreased diffusing lung capacity of carbon monoxide (DLCO)

  • Histologic changes on biopsy (not typically performed)

  • Positive inhalation challenge (not typically performed).

Schuyler criteria[45]

Major:

  • Compatible symptoms

  • Positive natural challenge

  • Bronchoalveolar lavage shows lymphocytosis

  • Compatible findings on chest imaging study

  • Evidence of exposure to known cause of HP by history or antibody presence

  • Pulmonary histology consistent (not typically performed).

Minor:

  • Bibasilar rales

  • Decreased DLCO

  • Hypoxemia at rest or with exercise.

Keys to the diagnosis of HP: the role of serum precipitins, lung biopsy, and high-resolution computed tomography[46]

Major:

  • Compatible exposure

  • Inspiratory crackles

  • Lymphocytosis if bronchiolar lavage is performed

  • Dyspnea

  • Infiltrates on chest imaging study.

Minor:

  • Antibody positive to putative antigen

  • Decreased DLCO

  • Improvement with avoidance

  • Recurrent febrile episodes

  • Granulomas if lung biopsy performed; usually not necessary.

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