Analysis of Data and Probabilities
The International Labor Organization (ILO) classification of roentgenograms of the pneumoconioses provides a method for recording abnormalities of the lungs and pleura resulting from the inhalation of inorganic dusts. First developed in the 1950s, and subsequently modified, it allows classification of the roentgenographic changes due to asbestosis as well as due to coal workers’ pneumoconiosis and silicosis. In addition to the clinical implications of determining the presence of asbestosis, we are in an era when the worker may receive compensation for the deleterious effects resulting from occupational exposure to asbestos dust. Originally intended primarily for epidemiologic surveys, there has been a growing tendency over the past 30 years to accept the ILO classified chest roentgenogram of an individual as the sole indicator of the presence or absence of asbestos-induced lung disease at the histologic level, giving the ILO classification an important role in reaching compensation decisions.
The extension of the ILO classification from its traditional role as an epidemiologic survey tool to its application to individual patients makes it imperative that we re-evaluate the significance of the ILO reading, especially in the diagnosis of early or evolving asbestosis in view of data which have emerged concerning the lack of roentgenographic-histologic correlation.
We have become aware that the chest roentgenogram tends to underestimate the presence of early interstitial lung disease. It is our purpose here to discuss those factors which lead to the underestimation of early asbestosis by the ILO classification and to calculate the frequency with which this may occur. in detail
Problems with the Application of the ILO Classification to Individual Subjects
Many factors may make the application of the ILO classification to individual roentgenographic examinations of limited value in early asbestosis. In order to understand these factors, we reviewed the literature in search of studies describing the variables which affect the roentgenographic visualization of interstitial fibrosis. We also analyzed from the literature, as well as from our own clinical material, data describing the roentgenographic-histologic correlations in asbestos-induced lung disease.