Exclusion of other known causes of interstitial lung diseases, such as certain drug toxicities,
environmental exposures, and connective tissue diseases
Abnormal pulmonary function studies that include evidence of restriction (reduced vital capacity
often with an increased FEV1:FVC ratio) and impaired gas exchange (increased AaPO2 with rest or
exercise or decreased DLCO)
HRCT scan showing bibasilar reticular abnormalities with minimal ground-glass opacities
Transbronchial lung biopsy or BAL showing no features to support another diagnosis
Minor Criteria
Age >50 years
Insidious onset of otherwise unexplained dyspnea on exertion
Duration of illness greater than or equal to 3 months
Bibasilar inspiratory crackles (dry or "Velcro-like" in quality)
AaPO2 = alveolar/arterial pressure difference for oxygen
DLCO = diffusing capacity of the lung for carbon monoxide
FEV1 = forced expiratory volume in 1 second
FVC = forced vital capacity
