Pulmonary inflammation in asbestos-exposed subjects with borderline parenchymal changes on HRCT

Many asbestos-exposed subjects have minor parenchymal changes on high resolution computed tomography (HRCT) that do not fulfil the diagnostic criteria for pulmonary fibrosis and asbestosis. We investigated if these borderline parenchymal changes in asbestos-exposed subjects are related to pulmonary inflammatory activity.

Exhaled nitric oxide was measured, exhaled breath condensate collected and HRCT scanned in 104 subjects with moderate to high occupational asbestos exposure. Forty-one healthy unexposed subjects served as a comparison group.

After excluding other pulmonary diseases, 35 asbestos-exposed subjects had normal parenchymal findings and 31 subjects had borderline parenchymal changes on HRCT. Lung function was poorer in the latter group, but there was no difference in the degree of asbestos exposure between these groups. As compared with the unexposed comparison group, asbestos-exposed subjects with borderline parenchymal changes had increased alveolar NO concentration (3.0 ± 0.2 vs. 2.3 ± 0.1 ppb, p = 0.008) and increased levels of leukotriene B4 (12.2 ± 1.1 vs. 3.3 ± 0.8 pg/ml, p < 0.001) and 8-isoprostane (9.4 ± 0.7 vs. 7.3 ± 0.6 pg/ml, p = 0.021) in breath condensate. Asbestos-exposed subjects with normal parenchymal findings had only increased breath condensate levels of leukotriene B4 (11.4 ± 0.9, p < 0.001).

Borderline parenchymal changes on HRCT in asbestos-exposed subjects are associated with increased markers of pulmonary inflammation. Such borderline parenchymal changes are likely a mild or early form of the same pathological process that leads to asbestosis.