Asbestos-related lesions of the pleura: parietal plaques compared to diffuse thickening studied with chest roentgenography, computed tomography, lung function, and gas exchange

Our plain-English summary of Asbestos-related lesions of the pleura: parietal plaques compared to diffuse thickening studied with chest roentgenography, computed tomography, lung function, and gas exchange, by G. Hillerdal, P. Malmberg, A. Hemmingsson (American Journal of Industrial Medicine, 1990).

The study

• Authors: G. Hillerdal, P. Malmberg, A. Hemmingsson
• Journal: American Journal of Industrial Medicine
• Published: 1990;18(6):627-39
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 003746).

Abstract

Lung function tests, tests of working capacity with gas exchange, and computed tomography (CT) with density measurements with the patient supine and prone were performed in 23 males with asbestos-related bilateral pleural lesions. Two had pulmonary asbestosis grade 1/0 or more; all the others had normal lung parenchyma. On x-ray, the pleural lesions were divided into plaques involving only the parietal pleura There was a and diffuse pleural fibrosis of various degrees involving the visceral pleura. There was a good correlation between the findings at plain chest roentgenography and CT, but more lesions were seen on the CT scan. However, a few pleural plaques seen on conventional films were not observed at CT. Individuals with plaques had slightly lowered lung function compared to reference subjects. Bilateral diffuse pleural fibrosis was associated with a marked decrease in pulmonary function. The two patients with radiologically evident pulmonary asbestosis were found in this group. Decreased lung function was also observed in subjects with pleural fibrosis of only grade 1 (involving less than one fourth of the hemithorax) and a normal exercise capacity. The study shows the importance of differentiation between various asbestos-related pleural lesions.

In plain English

This Swedish study examined 23 men with occupational asbestos exposure and pleural changes on both sides of the chest. Based on standard chest X-rays, 13 had pleural plaques, 3 had diffuse pleural fibrosis on one side and 7 on both sides. Both men with pulmonary asbestosis were in this last group. Exposure was described as moderate, intermittent or daily; fiber types were not named. CT confirmed the plaques in all but two patients and often showed more advanced lesions, but no more asbestosis than X-rays. Compared with a non-exposed control population, the plaque group had slightly impaired lung function. Even the four men with the mildest grade of fibrosis on both sides had significantly lower results than the plaque group on several breathing measures. The three with more extensive fibrosis were much more impaired. The authors concluded that plaques and diffuse fibrosis should be told apart, and that CT was not a reliable way to detect early lung fibrosis, though this did not necessarily apply to high-resolution CT, which they did not use.

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 comparison study of a small group of patients with different types of asbestos-related pleural lesions, using chest X-ray, CT, lung function tests and exercise gas-exchange tests
• Who was studied: 23 male patients up to 70 years of age, seen in the pulmonary department of the university hospital in Uppsala, Sweden. All had a history of occupational asbestos exposure and bilateral pleural lesions considered due to that exposure. Study dates not stated.
• Exposure: Occupational asbestos exposure, fiber type not stated. Plaque group: 7 with moderate, intermittent exposure (mean 29 years) and 6 with moderate daily exposure (mean 15 years). Bilateral diffuse fibrosis group: 3 intermittent (mean 19 years) and 4 daily (mean 15 years). Unilateral group: all 3 intermittent (mean 25 years).
• Main results:
  • On standard X-ray, 13 patients were classified as having pleural plaques, 3 as unilateral diffuse pleural fibrosis and 7 as bilateral diffuse pleural fibrosis.
  • Only two patients had pulmonary asbestosis. Both were in the bilateral diffuse pleural fibrosis group, and no other patient showed small opacities on the standard film.
  • Plaques seen on plain X-ray were confirmed on CT in all patients except two, and usually looked more extensive on CT.
  • In the diffuse fibrosis groups, CT often showed more advanced pleural lesions than the X-ray.
  • CT did not show more evidence of pulmonary asbestosis than the standard film.
  • As a group, patients with pleural plaques had slightly impaired lung function compared with a non-exposed control population.
  • The four patients with only grade 1 bilateral diffuse fibrosis had significant decreases, compared with the plaque group, in FEV1, FEV1/VC, FEF50 and MEF/FEF50. Their decrease in total lung capacity approached statistical significance.
  • The three patients with grade 2 or 3 bilateral diffuse fibrosis had much more impaired lung function. This group included the two patients with asbestosis.
  • Lung function correlated with X-ray findings. The best correlation was between the degree of right-sided diffuse pleural fibrosis and MEF/FEF50 (r = 0.9).
  • Gas exchange during maximal work differed significantly between the plaque group and the diffuse fibrosis groups.
  • On CT density measurements with the patient supine, the front-to-back difference in lung density differed significantly between the plaque group and the bilateral diffuse fibrosis group (P < 0.05).
  • CT density measures showed no or only weak correlations with lung function and working capacity. The best was r = 0.52.
• The authors' conclusion: The authors concluded that it is important to distinguish parietal pleural plaques from visceral pleural lesions (diffuse pleural fibrosis). They also concluded that CT was not a reliable method for detecting early pulmonary fibrosis in asbestos-exposed patients. They stated that this conclusion does not necessarily apply to high-resolution CT, which they did not use.
• Limitations the authors state:
  • The groups were small: the significant findings in the grade 1 bilateral fibrosis group came from only four subjects.
  • Patients were grouped using standard X-rays, and CT showed that a few were misclassified, though the authors state this was not reflected in lung function values.
  • High-resolution CT was not used, and the authors state their conclusions do not necessarily apply to it.

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: Pleura, Bilateral, Asbestosis, Parenchyma, Parietal Pleura, Fibrosis, Visceral Pleura, CT Scan.

Related studies

• Focal pleural thickening mimicking pleural plaques on chest computed tomography: tips and tricks — K.M. Alfudhili, D.A. Lynch, et al. (2016)
• Asbestos-related pleural diseases: dimensional criteria are not appropriate to differentiate diffuse pleural thickening from pleural plaques — J. Ameille, M. Matrat, et al. (2004)
• 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 — S. Neri, A. Antonelli, et al. (1994)
• 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)
• Asbestos-related diffuse pleural thickening — N. Fujimoto, K. Kato, et al. (2014)

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