Diagnosis and classification of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis is a difficult disease to diagnose. Idiopathic pulmonary fibrosis is a member of a class of diseases known as idiopathic interstitial pneumonias. Other members include nonspecific interstitial pneumonia, cryptogenic organizing pneumonia, acute interstitial pneumonia, respiratory bronchiolitis-associated interstitial lung disease, desquamative interstitial pneumonia, and lymphocytic interstitial pneumonia. Usual interstitial pneumonia (UIP) is the pathological equivalent of idiopathic pulmonary fibrosis. Prior to 2011, the diagnosis was based on major and minor criteria, but because these criteria were not evidence based, the criteria were modified by consensus from the American Thoracic Society, the European Respiratory Society, the Japanese Respiratory Society, and the Latin American Thoracic Association. These new criteria now include satisfying three core requirements, including exclusion of other possible cause of interstitial lung disease, specific findings of usual interstitial pneumonia on high resolution computed tomography, and a combination of "possible UIP" findings on high resolution computed tomography and UIP findings on lung biopsy. Idiopathic pulmonary fibrosis is a severe, progressive disease with limited treatment options, and exacerbations are associated with a high degree of morbidity and mortality.