Role of computed tomography in evaluating asbestos related lung disease

Our plain-English summary of Role of computed tomography in evaluating asbestos related lung disease, by S. Lozewicz, R.H. Reznek, M. Herdman, et al (British Journal of Industrial Medicine, 1989).

The study

• Authors: S. Lozewicz, R.H. Reznek, M. Herdman, J.E. Dacie, A. McLean, R.J. Davies
• Journal: British Journal of Industrial Medicine
• Published: 1989;46(11):777-81
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000120).

Abstract

To find how computed tomography (CT) may be effectively used in individuals with suspected asbestos related lung disease 30 men with a history of exposure to asbestos were studied. All subjects underwent high kilovoltage posteroanterior and left lateral chest radiographs and chest CT. Eighteen were randomly selected asbestos workers referred for routine surveillance. The remaining 12 were patients who had been referred for investigation of respiratory symptoms or abnormal routine chest radiograph, or both, and found to have chest radiographic changes compatible with asbestos related lung disease. In the group referred for routine surveillance both pleural shadowing and pulmonary shadowing were shown on CT but not chest radiographs in only one case. Five were thought to have pleural shadowing on chest radiographs but this was confirmed on CT in only one case. All 12 patients referred for investigation showed pleural shadowing on chest radiographs; this was confirmed in all cases on CT which also showed unsuspected pulmonary shadowing in five cases. These findings suggest that it is not appropriate to use chest CT routinely in all asbestos workers referred for routine surveillance. When CT is used selectively in those with pleural shadowing on plain chest radiography, however, it is helpful in refuting or confirming the presence of pleural disease and may show unsuspected pulmonary shadowing.

In plain English

This study compared computed tomography (CT) scans with plain chest X-rays in 30 men exposed to asbestos at work. Eighteen were randomly selected asbestos workers referred for routine surveillance. The other 12 were referred patients whose X-rays showed changes compatible with asbestos related lung disease. In the surveillance group, X-rays were thought to show pleural shadows in five men, but CT confirmed pleural thickening in only one. CT showed pleural thickening missed by X-ray in only one worker, and lung shadowing compatible with asbestosis in one. In all 12 referred patients, CT confirmed the pleural thickening seen on X-ray. It also showed unsuspected lung shadowing compatible with asbestosis in five more. Across all 30 men, abnormal CT was significantly associated with lower lung volumes, yet seven of the 14 with abnormal CT had lung function in the normal range. The authors concluded that routine CT in surveillance was not justified, but that CT helps confirm or refute pleural disease when X-rays show pleural shadowing. They noted that CT's frequent finding of unsuspected lung shadowing might not apply to workers screened under current regulations, who likely had shorter, more recent exposure and more protective measures.

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: Clinical imaging comparison study: every subject had both plain chest radiographs and chest CT, read by separate radiologists
• Who was studied: 30 men at St Bartholomew's Hospital, London. 18 were randomly selected asbestos workers referred for routine surveillance under the Control of Asbestos at Work Regulations. 12 were patients referred to the department of respiratory medicine with a history of occupational asbestos exposure and chest radiograph changes compatible with asbestos related lung disease. Study dates are not given.
• Exposure: Occupational exposure to asbestos. No fiber types, products or doses are named. By the authors' account (table 1), the surveillance workers had shorter and more recent exposure than the referred patients.
• Main results:
  • Surveillance group (18 workers): the chest radiograph was thought to show pleural shadows in 5 workers, but only 1 of these showed pleural thickening on CT. The authors considered the other 4 probable false positives.
  • In 2 of those 4 surveillance workers, CT showed subpleural fat at the site that had looked like pleural thickening on the radiograph.
  • Surveillance group: pleural thickening was shown on CT but not on chest radiograph in only 1 worker.
  • Surveillance group: only 1 worker showed pulmonary shadowing on CT that was not seen on chest radiograph.
  • Referred patients (12): pleural thickening was seen in all 12 on both chest radiographs and CT.
  • Referred patients: asbestosis was thought present on chest radiographs in 2, both confirmed on CT. CT showed pulmonary shadowing compatible with asbestosis in a further 5 of the 12.
  • Surveillance group: right and left oblique chest radiographs, done in 12 workers, added no information beyond the PA and left lateral films.
  • All 30 subjects: 14 had pleural thickening on CT, bilateral in 11. Of the 3 with pleural thickening on one side only, 1 had a histologically proved mesothelioma.
  • All 30 subjects: there was a significant association between pleural or pulmonary shadowing on CT and low lung volumes.
  • Of the 14 subjects with abnormal CT, 7 had lung function values within two standard deviations of predicted, which would be judged within the normal range.
  • None of the 18 subjects scanned both prone and supine showed abnormalities in gravity dependent perfusion.
• The authors' conclusion: The authors concluded that routine CT in the medical surveillance of asbestos workers under the 1987 Regulations is not justified. They also concluded that CT used selectively in those with pleural shadowing on plain chest radiography helps refute or confirm pleural disease and may show unsuspected pulmonary shadowing.
• Limitations the authors state:
  • The authors noted that the finding that CT often shows unsuspected pulmonary shadowing in patients with pleural shadowing may not apply to workers screened under current regulations. Those workers likely had shorter exposure and were more likely to have used protective measures.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Chest X-Ray.

Related studies

• 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)
• High-resolution computed tomography of asbestos-related diseases — D.R. Aberle (1991)
• 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)
• Agreement between chest radiography and high-resolution computed tomography in diagnosing dust-related interstitial lung fibrosis — R.R. Tiwari (2015)
• Diagnostic Performance of Ultra-Low-Dose Computed Tomography for Detecting Asbestos-Related Pleuropulmonary Diseases: Prospective Study in a Screening Setting — M. Schaal, F. Severac, et al. (2016)

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