Early clinical studies on relatively small populations of patients concluded that CT was able to detect early fibrosis, even when the findings from conventional roentgenograms and pulmonary function tests were normal or inconclusive. The signs on CT purported to have an association with asbestosis included (1) thickening of septa, (2) parenchymal linear densities, (3) subpleural dependent density, (4) curvilinear subpleural lines, (5) honeycombing, and (6) pleural thickening.
The purpose of this study was to examine the pathologic findings associated with pleural plaques, in order to determine what significance the presence of pleural plaques should be given in establishing the diagnosis of asbestosis, and to search for histologic changes associated with exposure to asbestos which might be detected radiographically. further
We found that while the presence of pleural plaques was associated with peribronchiolar fibrosis, a significant percentage (47 percent; 44/93) of the patients with pleural plaques did not have peribronchiolar fibrosis. Indeed, peribronchiolar fibrosis with associated asbestos bodies (asbestosis) was found in only 6 percent (6/93) of the patients with pleural plaques. Pleural plaques therefore cannot be used as an absolute marker of parenchymal disease.
While not diagnostic for asbestosis, the presence of pleural plaques was highly correlated with peribronchiolar fibrosis, large scars, pleural thickening, organizing pneumonia, and scar-related emphysema. The presence of pleural plaques has itself been shown to be correlated with exposure to asbestos. Our findings of an association between these various forms of pulmonary fibrosis and pleural plaques therefore confirms previous studies which have implicated asbestos as a cause of pulmonary fibrosis.