Major criteria:
(1) evidence of exposure to an offending antigen (based on history, demonstration of antibody or measurement of micro-organisms)
(2) symptoms compatible with allergic alveolitis (fever, chills, malaise, dry cough, dyspnea), appearing or worsening some hours after antigen exposure
(3) chest radiographic changes compatible with allergic alveolitis (patchy, ill-defined parenchymal densities; interstitial strands)
Minor criteria:
(1) basal crepitating rales on lung auscultation
(2) impairment of pulmonary diffusion capacity
(3) decrease in PaO2 at rest or during exercise
(4) restrictive lung changes on spirometry
(5) lung biopsy changes compatible with allergic alveolitis (acute granulomatous interstitial pneumonitis with macrophages, foreign body giant cells, neutrophils and eosinophils)
(6) positive provocation test (work exposure, inhalation challenge)
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Diagnosis
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Features
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confirmed
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all major criteria
2 or more minor criteria
exclusion of other lung diseases
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confirmed
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first 2 major criteria met
normal chest X-ray with lung biopsy compatible with hypersensitivity pneumonitis
2 or more minor criteria (in addition to lung biopsy findings)
exclusion of other lung diseases
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