Thin-section CT abnormalities and pulmonary gas exchange impairment in workers exposed to asbestos

Our plain-English summary of Thin-section CT abnormalities and pulmonary gas exchange impairment in workers exposed to asbestos, by A. Sette, J.A. Neder, L.E. Nery, et al (Radiology, 2004).

The study

• Authors: A. Sette, J.A. Neder, L.E. Nery, J. Kavakama, R.T. Rodrigues, M. Terra-Filho, S. Guimarães, E. Bagatin, N. Müller
• Journal: Radiology
• Published: 2004;232(1):66-74
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To evaluate the relationship between abnormalities at thin-section computed tomography (CT) and indexes of pulmonary gas exchange impairment at rest and during moderate exercise in workers exposed to asbestos.

Materials And Methods: Eighty-two workers with long-term exposure to asbestos and abnormal thin-section CT findings underwent respiratory physiologic measurements at rest (lung diffusing capacity, Dlco) and during exercise (oxygen uptake-corrected alveolar-arterial pressure difference for oxygen, DeltaP[A-a]O(2)/VO(2)). CT results were compared with physiologic measurements of impairment in gas exchange (Dlco < 70% predicted value and/or DeltaP[A-a]O(2)/VO(2) > 20 mm Hg. L. min(-1)). The CT findings were divided into five categories by using a previously described method. Odds ratios and 95% CIs for gas exchange defects were calculated for patients grouped according to CT findings. Logistic regression analysis was performed with gas exchange as the dependent response and CT abnormalities as independent variables.

Results: A significant association was found between extent of disease at CT and impairment of gas exchange (P <.01). Probability of functional impairment was increased with multifocal (class II) and diffuse (class III) CT abnormalities, particularly when several lesion types were found concomitantly. Logistic regression analysis demonstrated significant association of parenchymal bands (odds ratio, 6.20; 95% CI: 1.99, 19.22) and subpleural nodules (odds ratio, 3.83; 95% CI: 1.23, 11.89) with functional impairment. Presence and number of pleural plaques did not improve model accuracy for gas exchange impairment prediction (P >.05).

Conclusion: Thin-section CT grading of interstitial lung disease is useful in assessing the likelihood of pulmonary gas exchange impairment at rest (Dlco) and during exercise (DeltaP[A-a]O(2)/VO(2)) in workers with long-term asbestos exposure.

Copyright RSNA, 2004

In plain English

This prospective cross-sectional study examined whether findings on thin-section CT scans of the lungs were related to how well the lungs transfer oxygen into the blood (gas exchange). Gas exchange was measured at rest and during moderate exercise on a bicycle. The study included 82 asbestos-cement workers and chrysotile miners referred for impairment evaluation, all of whom had abnormal CT scans. By the authors' definition, 23 workers had clinically significant gas exchange impairment. In the two most advanced CT groups (D and E), 15 of 29 workers were impaired, with odds ratios of 2.79 (95% CI 1.14 to 8.90) and 4.71 (95% CI 1.43 to 15.52). Two CT findings were associated with impairment: parenchymal bands (odds ratio 6.20; 95% CI 1.99 to 19.22) and subpleural nodules (odds ratio 3.83; 95% CI 1.23 to 11.89). Pleural plaques did not improve the model's prediction. The authors concluded that thin-section CT grading of interstitial lung disease is useful in assessing the likelihood of gas exchange impairment. They noted that requiring an abnormal CT for entry biased comparisons in favor of CT, and that emphysema was not formally scored.

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: prospective cross-sectional study
• Who was studied: 87 workers were consecutively referred for impairment evaluation: 57 asbestos-cement workers and 30 chrysotile miners. Five were excluded for advanced cardiovascular disease, leaving 82 subjects aged 41 to 82 years (mean 64.1), all with abnormal thin-section CT findings. The authors are affiliated with institutions in Brazil. Study dates are not given.
• Exposure: Work in asbestos-cement manufacturing or chrysotile mining. Subjects had at least 1 year of asbestos exposure (mean 13.8 years) and more than 15 years since exposure began. The authors pooled the two settings after finding no significant difference in gas exchange variables between them.
• Main results:
  • 23 of the 82 workers had clinically significant pulmonary gas exchange impairment. This was defined as diffusing capacity (DLCO) below 70% of predicted and/or an exercise rise in the alveolar-arterial oxygen gradient, corrected for oxygen uptake, above 20 mm Hg per L per min. That is a prevalence of 28%.
  • In CT groups D and E combined, 15 of 29 workers had gas exchange impairment (positive predictive value 51.7%).
  • CT group D (grade II, three or more abnormalities): 7 of 15 impaired, odds ratio 2.79 (95% CI 1.14, 8.90).
  • CT group E (grade III, four or more abnormalities): 8 of 14 impaired, odds ratio 4.71 (95% CI 1.43, 15.52).
  • CT group A (grade I, a few sites of abnormality): 2 of 21 impaired, odds ratio 0.20 (95% CI 0.04, 0.94).
  • In the intermediate CT groups B and C, CT results were not conclusive, but 26 of 32 workers did not have gas exchange dysfunction.
  • Chest radiography group II (ILO profusion 2/1 or greater): 6 of 8 impaired, odds ratio 7.57 (95% CI 1.42, 40.52).
  • In logistic regression, parenchymal bands were significantly associated with gas exchange impairment: odds ratio 6.20 (95% CI 1.99, 19.22).
  • In logistic regression, subpleural nodules were significantly associated with gas exchange impairment: odds ratio 3.83 (95% CI 1.23, 11.89).
  • Presence and number of pleural plaques did not improve the model's accuracy in predicting gas exchange impairment (not statistically significant).
  • Extent of CT abnormalities was not correlated with any clinical variable, including smoking history and years of asbestos exposure.
• The authors' conclusion: The authors concluded that thin-section CT grading of interstitial lung disease is useful in assessing the likelihood of pulmonary gas exchange impairment at rest and during exercise in workers with long-term asbestos exposure.
• Limitations the authors state:
  • Only workers with abnormal thin-section CT were included. This biased the study toward CT performing better than chest radiography.
  • Only pleural plaques were analyzed. Diffuse pleural thickening was not assessed.
  • Emphysema was not formally scored and may have confounded the results.
  • Testing at submaximal rather than maximal exercise may have reduced sensitivity for detecting physiologic impairment.

Topics

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

Medical terms in this study, explained in our Lexicon: Diffusing Capacity (DLCO), Odds Ratio, Pleural Plaques, Interstitial Lung Disease, Asbestos Exposure.

Related studies

• Screening of miners and millers at decreasing levels of asbestos exposure: comparison of chest radiography and thin-section computed tomography — M. Terra-Filho, E. Bagatin, et al. (2015)
• Asbestos-induced and smoking-related disease: apportioning pulmonary function deficit by using thin-section CT — S.J. Copley, Y.C. Lee, et al. (2007)
• Lung diffusing capacity relates better to short-term progression on HRCT abnormalities than spirometry in mild asbestosis — C.R. Nogueira, L.M. Nápolis, et al. (2011)
• 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)
• Risk and significance of chest radiograph and pulmonary function abnormalities in an elderly cohort of former nuclear weapons workers — M.A. Mikulski, P.G. Hartley, et al. (2011)
• Asbestosis, pulmonary symptoms and functional impairment in shipyard workers — K.H. Kilburn, R. Warshaw, et al. (1985)

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