Pleural plaques and asbestosis: dose- and time-response relationships based on HRCT data

Most studies on asbestos-related diseases are based on chest radiographs, and dose-response relationships are still controversial. The aim of this study was to describe the most relevant parameters of asbestos exposure linked to pleural plaques and asbestosis diagnosed by high-resolution computed tomography (HRCT). A large screening programme including systematic HRCT examinations was organised from 2003 to 2005 in France for formerly asbestos-exposed workers. The time since first exposure (TSFE), level, duration and cumulative exposure to asbestos were used in adjusted unconditional logistic regression to model the relationships of the two diseases. Analysis of a population of 5,545 subjects demonstrated that TSFE (p<0.0001) and cumulative exposure (p = 0.02) (or level, depending on the models used), were independently associated with the frequency of pleural plaques. Only cumulative exposure (p<0.0001) or level of exposure (p = 0.02) were significantly associated with asbestosis. All trend tests were significant for these parameters. To date and to our knowledge, this study is the largest programme based on HRCT for the screening of asbestos-exposed subjects. Both time-response and dose-response relationships were demonstrated for pleural plaques, while only dose-response relationships were demonstrated for asbestosis. These parameters must be included in the definition of high-risk populations for HRCT-based screening programmes.