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It has been stated that "The interpretation of films for pneumoconiosis requires profound knowledge and perspicacity and that the ideal interpreter is a happy blend of Sherlock Holmes, Albrecht Durer and Socrates."' This trio's knowledge and perspicacity would certainly be applicable to the standard tool for interpreting chest films for pneumoconioses, the International Labour Office (ILO) Classification of Pneumoconioses, last revised in 19802 and overdue for revision. The major advances in this scheme have been the inclusion of linear or "irregular" opacities to describe the interstitial fibrosis (IF) of asbestosis, increasing attention to pleural fibrosis (characterized as "thickening" and seen predominantly in asbestosexposed persons), and refinement of the quantitative scale for profusion (number) of opacities from 4 points to 12.
A number of investigations in the last decade using the varied disciplines of high resolution computerized tomography (HRCT), pulmonary physiology, and analysis of mortality have provided new perspectives on the correlation of the ILO readings (most importantly, the profusion score for irregular opacities, hereafter called "score") with other measures of the impact of asbestos-related pleuropulmonary fibrosis on the lung and on the patient. The study by Oksa and colleagues in this issue of CHEST (see page 1517) provides an opportunity to evaluate this information.
Since 1930, successive revisions have altered the standardized scheme for interpreting chest films for pneumoconioses. Several basic investigations correlated workplace dust exposure, lung dust burden, and/or tissue response with the profusion score then in use, generally the 4-point score. The assumption was that "the more fibrosis present, the more retained dust"3 in the lung. These investigations were directed at coal workers' pneumoconiosis (reviewed by Fernie and Buckley-4 and Vallyathan and colleagues5) and to a lesser extent, at silicosis6 8 and asbestosis.9,10 Indeed, asbestosis is different from the nodular pneumoconioses in its less consistent relationship of dust burden to histologic severity, and in the greater impact of its "irregular" IF on lung function. That radiographic abnormality carries with it a far greater effect on lung function in asbestosis than in the nodular pneumoconioses was recognized early in the history of asbestosis.9,10
In coal workers' pneumoconiosis and silicosis, the amount of dust and the severity of histologic fibrosis parallel each other.11,12 In addition, investigations have demonstrated consistent correlations between mineral content on the...