Asbestos-related pleural plaques on CT-scan and lung function

Introduction
Whether isolated pleural plaques cause functional impairment remains controversial. The aim of this study was to analyse the relationships between isolated pleural plaques confirmed by CT-scan and lung function among subjects occupationally exposed to asbestos.

Methods
The study population consisted of 2,743 subjects, presenting with no parenchymal interstitial abnormalities on high resolution computed tomography (HRCT). Asbestos exposure was evaluated with calculation of an individual cumulative exposure index (CEI). Each included subject underwent pulmonary function tests (PFTs) and HRCT. PFTs variables were adjusted for age, smoking status, body mass index, CEI to asbestos and the centres in which PFTs were conducted.

Results
All studied functional parameters were within normal limits for subjects presenting with isolated pleural plaques and for subjects presenting with no pleuropulmonary abnormalities. However, isolated parietal and/or diaphragmatic pleural plaques were associated, when compared to subjects free of pleural plaques, with a significant decrease in total lung capacity (TLC; p=0.049), forced vital capacity (FVC; p<0.001) and FEV1 (p=0.003). In contrast, no significant relationship was observed between pleural plaques and FEV1/FVC ratio, forced expiratory flow (FEF)25-75 and residual volume (RV) impairment. A significant correlation was found between the extent of pleural plaques and the reduction in FVC and TLC whereas plaque thickness was not related to functional impairment.

Discussion
Our results show a relationship between isolated parietal and/or diaphragmatic pleural plaques and a trend towards a restrictive pattern, although the observed decrease in FVC and TLC is unlikely to be of real clinical relevance for the majority of subjects of this series.