Inter-reader agreement in HRCT detection of pleural plaques and asbestosis in participants with previous occupational exposure to asbestos.

OBJECTIVES: To investigate inter-reader agreement for the detection of pleural and parenchymal abnormalities using CT in a large cross-sectional study comprising information on individual cumulative exposure to asbestos. METHODS: The project was approved by the hospital ethics committee, and all patients received information on the study and gave their written informed consent. In 5511 CT scans performed in a cohort of retired workers previously exposed to asbestos and volunteering to participate in a multiregional survey programme (Asbestos Related Diseases Cohort, ARDCO), double randomised standardised readings, triple in case of disagreement, were performed by seven trained expert radiologists specialised in thoracic imaging and blind to the initial interpretation. Inter-reader agreement was evaluated by calculating the κ-weighted coefficient between pairs of expert readers and results of routine practice and final diagnosis after expert reading. RESULTS: κ-Weighted coefficients between trained experts ranged from 0.28 to 0.52 (fair to good), 0.59 to 0.86 (good to excellent) and 0.11 to 0.66 (poor to good) for the diagnosis of asbestosis, pleural plaques and fibrosis of the visceral pleura, respectively. κ-Weighted coefficients between results of routine practice and final diagnosis after expert reading were 0.13 (poor), 0.53 (moderate) and 0.11 (poor) for the diagnosis of asbestosis, pleural plaques and fibrosis of the visceral pleura, respectively. CONCLUSIONS: Interpretation of benign asbestos-related thoracic abnormalities requires standardisation of the reading and trained readers, particularly for participants asking for compensation, and with a view to the longitudinal survey of asbestos-exposed workers.

Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis?

BACKGROUND: It is uncertain whether isolated pleural plaques cause functional impairment. OBJECTIVE: To analyse the relationship between isolated pleural plaques confirmed by CT scanning and lung function in subjects with occupational exposure to asbestos. METHODS: The study population consisted of 2743 subjects presenting with no parenchymal interstitial abnormalities on the high-resolution CT (HRCT) scan. Asbestos exposure was evaluated by calculation of an individual cumulative exposure index (CEI). Each subject underwent pulmonary function tests (PFTs) and HRCT scanning. Variables were adjusted for age, smoking status, body mass index, CEI to asbestos and the centres in which the pulmonary function tests were conducted. RESULTS: All functional parameters studied were within normal limits for subjects presenting with isolated pleural plaques and for those presenting with no pleuropulmonary abnormalities. However, isolated parietal and/or diaphragmatic pleural plaques were associated with a significant decrease in total lung capacity (TLC) (98.1% predicted in subjects with pleural plaques vs. 101.2% in subjects free of plaques, p=0.0494), forced vital capacity (FVC) (96.6% vs. 100.4%, p<0.001) and forced expiratory volume in 1 s (FEV(1)) (97.9% vs. 101.9%, p=0.0032). In contrast, no significant relationship was observed between pleural plaques and FEV1/FVC ratio, forced expiratory flow at 25-75% FVC and residual volume. 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. CONCLUSIONS: The 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 in this series.

Does asbestos exposure cause airway obstruction, in the absence of confirmed asbestosis?

RATIONALE: Whether occupational exposure to asbestos causes airway obstruction remains controversial. OBJECTIVES: This study evaluated lung function in relation to cumulative exposure to asbestos in a large cohort of retired or unemployed workers exposed to asbestos. METHODS: The study population consisted of 3,660 volunteer subjects. An individual cumulative exposure index to asbestos was calculated for each subject, and information was obtained on smoking status. Pulmonary function tests were performed in all subjects; high-resolution chest computed tomography was also performed in 3,335 subjects. MEASUREMENTS AND MAIN RESULTS: Values of FEV(1)/FVC and FEF(25-75%) did not differ between five classes (quintiles) of cumulative exposure to asbestos, and no significant correlation was observed between cumulative exposure to asbestos and pulmonary function parameters, after adjustment for sex, tobacco consumption, emphysema, and body mass index. Furthermore, the proportion of abnormal pulmonary function tests did not differ between the five classes of cumulative exposure to asbestos. CONCLUSIONS: The results do not support a causal relationship between asbestos exposure alone and airway obstruction. However, the study sample may not be representative of all people occupationally exposed to asbestos, because a fraction of subjects with previously diagnosed asbestosis probably did not participate in this screening program.

Pleural plaques and the risk of pleural mesothelioma.

BACKGROUND: The association between pleural plaques and pleural mesothelioma remains controversial. The present study was designed to examine the association between pleural plaques on computed tomography (CT) scan and the risk of pleural mesothelioma in a follow-up study of asbestos-exposed workers. METHODS: Retired or unemployed workers previously occupationally exposed to asbestos were invited to participate in a screening program for asbestos-related diseases, including CT scan, organized between October 2003 and December 2005 in four regions in France. Randomized, independent, double reading of CT scans by a panel of seven chest radiologists focused on benign asbestos-related abnormalities. A 7-year follow-up study was conducted in the 5287 male subjects for whom chest CT scan was available. Annual determination of the number of subjects eligible for free medical care because of pleural mesothelioma was carried out. Diagnosis certification was obtained from the French mesothelioma panel of pathologists. Survival regression based on the Cox model was used to estimate the risk of pleural mesothelioma associated with pleural plaques, with age as the main time variable and time-varying exposure variables, namely duration of exposure, time since first exposure, and cumulative exposure index to asbestos. All statistical tests were two-sided. RESULTS: A total of 17 incident cases of pleural mesothelioma were diagnosed. A statistically significant association was observed between mesothelioma and pleural plaques (unadjusted hazard ratio (HR) = 8.9, 95% confidence interval [CI] = 3.0 to 26.5; adjusted HR = 6.8, 95% CI = 2.2 to 21.4 after adjustment for time since first exposure and cumulative exposure index to asbestos). CONCLUSION: The presence of pleural plaques may be an independent risk factor for pleural mesothelioma.