Idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) is a progressive interstitia pulmonary disease of unknown etiology. Since Hamman's and Rich's (1944) reports, many studies have tried to find a histological marker for the correlation between prognosis and response to therapy. However, there are many doubts regarding pathogenesis. In addition, it is generally accepted that response to therapy is related to the relative degree of cellularity and fibrosis. The purpose of this study is to describe the results of inflammatory/exudative changes, fibrotic/reparative changes, and airway alterations, using a semi-quantitative method by independent evaluation of two pathologists, in 24 open lung biopsies with the diagnosis of idiopathic pulmonary fibrosis. Fourteen histological features were analyzed using the 0 to 5 scale for interstitial alterations and the 0 to 2 scale for the airway changes. There was significant interobserver agreement for all histological features with Kw (Kappa) variations between 0.47 and 0.92. There was significant disagreement only for septal inflammatory intensity analysis, suggesting that these features must be discussed by the pathologists. The semi-quantitative method assessment was effective.

Keywords: Idiopathic pulmonary fibrosis (IPF). Usual interstitial pneumonia (UIP). Semi-quantitative method assessment.