Factors associated with early-stage pulmonary fibrosis as determined by high-resolution computed tomography among persons occupationally exposed to asbestos.

Abstract

Asbestosis remains difficult to diagnose, particularly in its early stages. The aim of this study was to determine criteria for independently associated features of pulmonary fibrosis in high-resolution computed tomograms among persons occupationally exposed to asbestos. Retired persons with documented occupational asbestos exposure and no known asbestos-related diseases were assessed for occupational, clinical, functional respiratory, and chest X-ray criteria. In addition, they all underwent high-resolution computed tomography (HRCT) in the prone position. Altogether 51 (7.2%) of the 706 enrolled participants had features of pulmonary fibrosis consistent with asbestosis in the HRCT. Among those with small irregular opacities of <1/0 according to the 1980 International Labour Office Classification (ILO-C) in their X-rays, 5% had asbestosis in the HRCT. In a multivariate analysis, only age [odds ratio (OR) per year 1.08, 95% confidence interval (95% CI) 1.02-1.14], cumulative-exposure index (CEI) for asbestos (OR 6.4, 95% CI 1.5-28.4 for a CEI of > or =100 fibers/ml x years), and the presence of small irregular X-ray opacities of > or =1/0 ILO-C (OR 3.0, 95% CI 1.6-6.0) were independently associated with HRCT asbestosis. No combinations of these criteria simultaneously yielded high sensitivity and specificity for the diagnosis of early-stage HRCT asbestosis. Moreover, only 2% of the persons with a CEI of <25 fibers/ml x years had HRCT asbestosis, the finding confirming the low incidence of asbestosis for such low exposure, as previously reported on the basis of X-ray data. Additional research is needed to better identify the persons most likely to benefit from HRCT screening for asbestosis.