The American Thoracic Society (ATS) has provided criteria for making the clinical diagnosis of idiopathic pulmonary fibrosis.


Major criteria:

(1) exclusion of other known causes of interstitial lung disease (drug toxicity, environmental exposures, connective tissue disease)

(2) abnormal findings on pulmonary function studies, including:

(2a) evidence of restriction (reduced vital capacity, often with an increase in the FEV1 to FVC ratio)

(2b) impaired gas exchange (increased alveolar-arterial oxygen gradient with rest or exercise, or a decreased diffusion capacity for carbon monoxide)

(3) bibasilar reticular abnormalities with minimal ground glass opacities on high-resolution computed tomography (HRCT)

(4) transbronchial lung biopsy or bronchoalveolar lavage (BAL) showing no features to support an alternative diagnosis


Minor criteria:

(1) age > 50 years

(2) insidious onset of unexplained dyspnea on exertion

(3) duration of illness for 3 or more months

(4) bibasilar inspiratory dry crackles ("Velcro type")


The clinical diagnosis of idiopathic pulmonary fibrosis:

(1) all 4 major criteria, AND

(2) >= 3 minor criteria


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