Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests

Our plain-English summary of Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests, by S. Neri, A. Antonelli, F. Falaschi, et al (Occupational and Environmental Medicine, 1994).

The study

• Authors: S. Neri, A. Antonelli, F. Falaschi, P. Boraschi, L. Baschieri
• Journal: Occupational and Environmental Medicine
• Published: 1994;51(4):239-43
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The lungs of 50 symptom free workers exposed to amosite and with normal pulmonary function tests were examined by high resolution computed tomography (HRCT). Twenty five had normal standard chest radiographs whereas the other 25 had radiographs interpreted as near normal (International Labour Office profusion score < 0/1 or suspected pleural plaques). In 13 of the workers the results of HRCT were negative; in 22 pleural plaques were found, in five there was only parenchymal involvement, and 10 had both pleural and parenchymal changes. The mean duration of exposure to amosite was significantly longer for the subjects with parenchymal signs than for those with normal parenchyma and for the workers with pleural plaques than for those with normal pleura and lung parenchyma. The prevalence of identified pleural and parenchymal abnormalities in the 50 workers was also significantly higher than in a reference group without exposure to asbestos. It is concluded that HRCT may detect initial lung and pleural involvement in symptom free workers exposed to amosite and the mean duration of exposure is longer for subjects with parenchymal or pleural involvement.

In plain English

This Italian study used high resolution computed tomography (HRCT) to scan 50 workers from a factory producing naval furniture, where a material containing about 40% amosite was used from 1958 to 1980. All had no symptoms and normal lung function tests. Twenty five had chest radiographs judged negative, and 25 had radiographs judged near normal. HRCT found pleural plaques only in 22 workers, lung tissue (parenchymal) changes only in five, both in 10, and nothing abnormal in 13. Four workers had a combination of signs the authors considered diagnostic of asbestosis. Among the 25 with negative radiographs, HRCT showed pleural plaques in 11 and both kinds of change in two. A reference group of 20 hospital patients without known asbestos exposure had significantly fewer findings. Mean exposure was 2.3 years for workers with normal HRCT, against 7.0 years for those with pleural changes and 11.0 years for those with both; these differences were significant. The authors concluded that HRCT can show lung or pleural involvement before symptoms appear. They noted that the meaning of isolated slight findings is not yet clear.

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: Study of HRCT findings in a selected group of exposed workers, compared with a reference group of unexposed hospital patients (the authors call it a "perspective study")
• Who was studied: 50 symptom free workers (49 men, mean age 45.7, range 31 to 61 years) with normal pulmonary function tests. They were selected from 127 workers at a naval furniture factory. 25 had chest radiographs confirmed negative and 25 had radiographs read as ILO profusion 0/1 or suspected pleural plaques. The reference group was 20 hospital patients (19 men, mean age 47.1) with no occupational or significant environmental asbestos exposure.
• Exposure: Amosite: a material containing about 40% amosite was used in the factory from 1958 to 1980, especially in the carpentry department to make panels with asbestos insulation between layers of wood. Mean exposure duration was 6.4 (SD 5.5) years, range 0.2 to 21 years. Mean time since first exposure was 20.7 (SD 5.0) years.
• Main results:
  • Of the 50 exposed workers, HRCT showed pleural plaques only in 22, parenchymal abnormalities only in five, both in 10, and no abnormality in 13.
  • In total, 32 exposed workers had pleural plaques, 23 of them on both sides. In nine workers the plaques were calcified.
  • Four exposed workers had two or more parenchymal signs, the combination the authors treated as diagnostic of asbestosis. No honeycombing was seen.
  • Among the 25 workers whose radiographs were confirmed negative, HRCT showed 11 cases of pleural plaques, two with both pleural and parenchymal involvement, and two with only a subpleural curvilinear shadow.
  • In the 20-patient reference group, HRCT found five cases of pleural plaques and parenchymal bands in one patient. Findings in the reference group were significantly less frequent than in the amosite exposed group (p less than 0.001).
  • Mean duration of exposure was 2.3 (SD 3.0) years for workers with normal HRCT, 7.0 (SD 5.5) years for those with pleural changes, 5.2 (SD 3.0) years for those with only parenchymal changes, and 11.0 (SD 5.2) years for those with both.
  • Exposure duration was significantly longer for workers with both pleural and parenchymal changes (p less than 0.005) and for those with pleural changes (p less than 0.05) than for workers with normal HRCT.
  • Workers with HRCT findings suggestive of pulmonary fibrosis had been exposed for 9.1 years, compared with 5.3 years for workers with normal parenchyma (p less than 0.05).
  • Standard chest radiographs were compared with HRCT, which was treated as the reference. For pleural findings, radiographs had sensitivity 89%, specificity 53% and accuracy 66%. For parenchymal findings, they had sensitivity 40%, specificity 97% and accuracy 80%.
• The authors' conclusion: The authors concluded that HRCT can show lung or pleural involvement in asbestos exposed workers before symptoms appear, and may allow asbestosis to be detected in some symptom free workers.
• Limitations the authors state:
  • The authors state that the specificity of HRCT findings in asbestosis is still a matter of controversy.
  • The findings in the control group may have causes other than asbestos, or may reflect asbestos exposure not known from the patients' histories.
  • The relevance of isolated slight HRCT findings in symptom free workers is not yet clear. The authors state there is no evidence that such findings progress or cause disability.
  • The comparison with radiographs artificially treated HRCT as the gold standard.
  • A subpleural curvilinear shadow on its own is not specific for asbestosis.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleura, Amosite, Chest X-Ray, Pulmonary Function Test (PFT), High-Resolution CT (HRCT), Pleural Plaques, Parenchyma.

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• The comparison of high-resolution computed tomography findings in asbestosis and idiopathic pulmonary fibrosis — M. Akira, K. Morinaga (2016)
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• High-resolution computed tomography abnormalities in ex-insulators annually exposed to asbestos dust — J.M. Soulat, D. Lauque, et al. (1999)

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