Computed tomography of asbestos-related pleural abnormalities

Our plain-English summary of Computed tomography of asbestos-related pleural abnormalities, by M. Tiitola, L. Kivisaari, A. Zitting, et al (International Archives of Occupational and Environmental Health, 2002).

The study

• Authors: M. Tiitola, L. Kivisaari, A. Zitting, M.S. Huuskonen, S. Kaleva, A. Tossavainen, T. Vehmas
• Journal: International Archives of Occupational and Environmental Health
• Published: 2002;75(4):224-8
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To study the observer agreement in several asbestos-related pleural abnormalities and to define criteria to discriminate between pleural changes in workers with occupational disease, and those in controls.

Methods: Pleural abnormalities in spiral computed tomography of 602 construction workers with asbestosis or bilateral pleural plaques and 49 controls were reviewed by three radiologists using structured forms.

Results: Intra- and inter-observer agreement (weighted kappa) was 0.4 or better with regard to the calcification, extent and thickness of pleural disease. These factors all correlated positively with the duration of asbestos exposure. There were significant differences in these pleural changes between the workers (mean extent per side 83 cm(2)) and controls (mean extent per side 40 cm(2)). Of the controls, 84% showed pleural lesions with an estimated extent of 10 cm(2) or more, bilateral in 64%. The extent of 45 cm(2) in pleural disease was the best value for discriminating between the controls and diseased workers, with a sensitivity of 82% and a specificity of 66%. The degree of pleural calcification, however, was the best discriminator between these groups, but quantitative methods are necessary for its use in the diagnostics of individuals.

Conclusions: The extent, calcification and thickness were well-repeatable indicators of benign pleural pathology and thus their use in future classification systems in computed tomography is recommended. In our material, the extent of 45 cm(2) and the degree of calcification were helpful in discriminating between pleural changes in workers with occupational disease, and those in controls who also presented marked pleural pathology.

In plain English

Finnish researchers reviewed CT scans of 602 construction workers diagnosed with asbestosis or bilateral pleural plaques. As controls, they used 49 male hospital patients scanned for suspected or known cancer outside the chest. Three radiologists read the scans separately. Their ratings of the extent, thickness and calcification of pleural disease (changes in the lung lining) were repeatable; ratings of adhesions and lung fissures were less so. Counting changes of 10 cm2 or more seen by at least two radiologists, bilateral changes appeared in 569 of 594 workers with data (95%) and 31 of 49 controls (64%). Mean extent per side of the chest was 83 cm2 in workers and 40 cm2 in controls. For extent, a cut-off of 45 cm2 best separated the groups (sensitivity 82%, specificity 66%), which the authors called modest. Calcification discriminated best overall but would need quantitative measurement for individuals. Longer exposure correlated with more pleural change. The authors recommended extent, calcification and thickness for future CT classification systems. They suggested the frequent changes in controls may reflect past wide use of anthophyllite asbestos in Finland and the sensitivity of CT.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Cross-sectional imaging study: three radiologists separately read CT scans, with observer-agreement analysis and a comparison of exposed workers with controls (including ROC analysis)
• Who was studied: 602 construction workers (591 men, 11 women, mean age 63, range 38 to 81) living in the Helsinki area. They were drawn from people with asbestos-related occupational disease identified in an earlier study of 18,900 asbestos-exposed persons. Among them were 85 cases of asbestosis and 601 cases of bilateral pleural plaques. The controls were 49 male hospital patients aged 50 to 75 who had chest CT because of suspected or known cancer outside the chest. Of these, 19 were judged unlikely to have been exposed to asbestos and 30 possibly exposed.
• Exposure: Occupational asbestos exposure in construction work, mostly for more than 20 years (mean 26). The work included installing heat and fire insulation or asbestos-containing walls and ceiling panels, using asbestos paints, putties and fillers, and dismantling or cleaning asbestos materials. The fiber types the workers were exposed to were not reported.
• Main results:
  • Readings of the extent, thickness and calcification of pleural disease were repeatable. Inter-observer and intra-observer weighted kappa values were: calcification 0.81 and 0.85, extent 0.75 and 0.54, average thickness 0.60 and 0.63, greatest thickness 0.60 and 0.72. Adhesions and inter-lobar fissure changes were less repeatable.
  • Pleural changes were counted when their extent was 10 cm2 or more and they were seen by at least two radiologists. On that basis, bilateral pleural changes were found in 64% of controls (31 of 49) and 95% of construction workers (569 of 594 with data; eight had missing data).
  • 84% of controls showed pleural pathology, most of it bilateral.
  • Mean extent of pleural disease per side of the chest was 83 cm2 in workers and 40 cm2 in controls. In the two control groups, mean extent was 40 cm2 (unlikely exposed) and 41 cm2 (possibly exposed). Differences between workers and controls were significant (P less than 0.001) for all studied pleural changes.
  • No differences in pleural pathology were found between the unlikely exposed and possibly exposed control groups.
  • Duration of asbestos exposure correlated positively with the pleural changes. Spearman correlations were 0.290 for calcification, 0.189 for maximal thickness, 0.127 for average thickness and 0.154 for extent.
  • In separating diseased workers from controls, areas under the ROC curve were 0.797 for calcification, 0.786 for maximal thickness, 0.752 for average thickness and 0.789 for extent.
  • For pleural extent, 45 cm2 was the best cut-off for separating the combined controls from the construction workers, with a sensitivity of 82% and a specificity of 66%.
  • The degree of pleural calcification was the best discriminator between the groups. The authors said quantitative methods would be needed to use it in diagnosing individuals.
• The authors' conclusion: The authors concluded that plaque extent, calcification and thickness were reliable indicators of benign pleural pathology and recommended their use in future CT classification systems. They suggested the high occurrence of plaques in controls may be due to past wide use of anthophyllite asbestos in Finland, and that it also reflects the high sensitivity of CT compared with radiography.
• Limitations the authors state:
  • The controls were patients with suspected malignant disease, not a cross-section of elderly Finnish people.
  • In a later detailed interview, minor asbestos exposure could not be ruled out in 30 of the controls.
  • Minimal pleural disease was hard to detect and could not reliably be told apart from partial volume effects from the muscles between the ribs, so a 10 cm2 threshold was used.
  • Separating pleural plaques from visceral (diffuse) pleural thickening was considered unreliable, so the extent measurement included both.
  • The 45 cm2 cut-off was a modest discriminator, with somewhat unsatisfactory specificity.
  • Workers and controls were scanned on different CT scanners. The authors thought this had little effect on the group differences.
  • Criteria for discriminating pleural changes are likely to be population specific and may vary between nations.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Occupational Disease, Bilateral, Pleural Plaques, Asbestos Exposure, Pleural Calcification, Pathology.

Related studies

• The usefulness of computed tomography in detecting asbestos-related pleural abnormalities in people who had indeterminate chest radiographs: the Libby, MT, experience — O.I. Muravov, W.E. Kaye, et al. (2005)
• Relationships (I) of International Classification of High-resolution Computed Tomography for Occupational and Environmental Respiratory Diseases with the ILO International Classification of Radiographs of Pneumoconioses for parenchymal abnormalities — T. Tamura, N. Suganuma, et al. (2015)
• Conventional and high resolution computed tomography in the diagnosis of asbestos-related diseases — D.A. Lynch, G. Gamsu, et al. (1989)
• Computed tomography in the diagnosis of asbestos-related thoracic disease — G. Gamsu, D.R. Aberle, et al. (1989)
• Emphysema findings associated with heavy asbestos-exposure in high resolution computed tomography of finnish construction workers — O. Huuskonen, L. Kivisaari, et al. (2004)
• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)

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