[Asbestos-related lesions detected by high-resolution CT scanning in asymptomatic workers. Specificity, relation to the duration of exposure and cigarette smoking].

The possibility to detect initial "preclinical" pulmonary lesions related to asbestos is under debate. The aim of this study is to report our experience. We have submitted to HRCT 70 shipyard workers with chest X-ray judged "normal" by "outside" readers (mean age 44.5 +/- 6.1 ys) with a similar grade of (low-level) exposure to amosite (mean duration of "direct"/"heavy" exposure was 4.2 +/- 4.9 ys; "environmental"/"light" exposure was 8.4 +/- 5.9 ys). Among the 70 workers, in 34 pleural plaques were shown, in 6 subjects parenchymal abnormalities alone and in 13 parenchymal and pleural abnormalities were found; in the last 17 workers no pathological finding was shown. In six subjects the presence of a combination of parenchymal abnormalities permitted us to diagnose asbestosis. The difference in the duration of exposure to asbestos for the subjects with both pleural and parenchymal involvement compared to all other groups of workers was statistically significant; also the difference in duration of exposure between workers with or without parenchymal involvement resulted significant. In a control group (20 subjects without any known professional exposure to asbestos) HRCT permitted us to identify 5 cases with small pleural plaques while only one case presented parenchymal bands; lesion frequency was significantly lower in comparison with the exposed group. Calcified plaques have been proved to be more common in the workers with heavier exposure, and no one of the reference group had calcified plaques. The CT-determined emphysema score was found to optimally correlate with smoking habit (pack/years). In conclusion our study suggests that pulmonary or pleural involvement can be shown by HRCT before the onset of any clinical symptomatology with high sensitivity and specificity. Furthermore the results seem to indicate that the prevalence of HRCT-shown parenchymal lesions and the severity of lung involvement among asbestos-exposed workers are related to the duration of exposure, as in most of clinically evident asbestos-related lung disorders, in contrast with previous observations.