Asbestos-induced and smoking-related disease: apportioning pulmonary function deficit by using thin-section CT

Our plain-English summary of Asbestos-induced and smoking-related disease: apportioning pulmonary function deficit by using thin-section CT, by S.J. Copley, Y.C. Lee, D.M. Hansell, et al (Radiology, 2007).

The study

• Authors: S.J. Copley, Y.C. Lee, D.M. Hansell, P. Sivakumaran, M.B. Rubens, A.J. Newman Taylor, R.M. Rudd, A.W. Musk, A.U. Wells
• Journal: Radiology
• Published: 2007;242(1):258-66
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To retrospectively correlate the extent of individual diseases seen at thin-section computed tomography (CT) with pulmonary function in an initial group of patients with asbestos-related parenchymal disease (asbestosis) and to test these findings in a subsequent group of patients whose CT scans were retrospectively identified.

Materials And Methods: This retrospective study had Institutional Review Board approval; informed consent was not required. The study included 133 individuals who had been exposed to asbestos. In the initial study group (81 patients; 79 men, two women; median age, 67 years), two observers used a CT scoring system to quantify the extent of pulmonary fibrosis, diffuse pleural thickening, small-airways disease, and emphysema. Multivariate equations were formulated by using independent CT variables to predict changes in total lung capacity (TLC) and carbon monoxide diffusing capacity (Dlco). The validity of these equations was then tested in a subsequent group of patients (52 patients; all men; median age, 60 years).

Results: At thin-section CT, the extent of asbestos-induced pleuropulmonary disease and emphysema correlated significantly with physiologic impairment (P<.001). Combined CT variables predicted 58% and 57% of the variability in TLC and Dlco, respectively, despite considerable variation in the proportion of coexisting pathologic conditions. When predictive equations with CT variables derived from the initial study group were applied to the subsequent study group, predicted TLC (rho=0.75, P<.001) and Dlco (rho=0.64, P<.001) correlated strongly with measured values.

Conclusion: The proposed CT system provides a semiquantitative method for assessing the relative contribution of asbestos-induced pleuropulmonary disease and smoking-related emphysema to functional impairment.

Copyright (c) RSNA, 2006.

In plain English

This retrospective study looked at 133 people with asbestos exposure, drawn from three specialist centers, whose thin-section CT scans showed asbestosis. In a first group of 81 patients (79 men, two women; 42 of them asbestos miners), two thoracic radiologists who did not see the clinical data scored the extent of lung fibrosis, emphysema and diffuse pleural thickening. The authors then related these scores to lung function tests. The extent of each of these three CT findings correlated significantly with impaired lung function. All CT features combined explained 58% of the variation in total lung capacity (TLC) and 57% of the variation in gas transfer (DLCO). Adding minor features gave little gain over the three main ones. The resulting equations were then tested in a second group of 52 men. There, the simpler three-feature equations accounted for up to 44% of the variation in TLC and 46% in DLCO. The authors concluded that their CT system offers a semiquantitative way to judge how much of the lung function loss comes from asbestos-related disease and how much from smoking-related emphysema. They noted the retrospective design, the lack of tissue proof of asbestosis, and wide confidence intervals.

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: Retrospective study correlating CT scoring with pulmonary function, with equations derived in an initial group and tested in a subsequent group
• Who was studied: 133 patients with asbestos exposure and CT features of asbestosis, identified from three specialist centers. 14 of 147 patients were excluded. The initial group was 81 patients (79 men, two women; median age 67, range 46 to 86) from two centers; all 42 patients from one of these centers were asbestos miners. The subsequent group was 52 consecutively identified men (median age 60, range 33 to 82) referred to a third center. Overall, 85% were present or past smokers. Study dates are not given.
• Exposure: Occupational asbestos exposure: asbestos mining (42 patients) and a variety of other asbestos-related industries (39 patients in the initial group). Fiber types and doses are not given. Smoking history was also recorded.
• Main results:
  • In the initial group, the strongest univariate correlations were between extent of fibrosis and TLC (Spearman 0.52) and DLCO (0.50); between extent of emphysema and KCO (0.48) and DLCO (0.34); and between extent of diffuse pleural thickening and FVC (0.50) and TLC (0.49).
  • In the initial group, comprehensive multiple regression using all scored CT variables gave R2 values of 0.58 for TLC, 0.57 for DLCO and 0.41 for KCO.
  • Including all ancillary CT features added little correlation beyond the three key features (fibrosis, emphysema, diffuse pleural thickening).
  • In the subsequent group of 52, the simplified three-feature equations gave correlations between predicted and observed values of 0.74 (TLC) and 0.64 (DLCO). They accounted for up to 44% of the variance in TLC and 46% of the variance in DLCO.
  • In the subsequent group, the comprehensive equations explained 52% of the variance in TLC, 40% in DLCO and 46% in FVC.
  • There was no relationship between the extent of fibrosis and the extent of emphysema on CT; this was also examined separately in the 43 patients with both.
  • After adjustment for other CT abnormalities, more extensive emphysema was associated with an increase in TLC. The authors described this as a deceptive preservation of lung volumes.
  • Coexisting emphysema was seen in 32% of the study population.
• The authors' conclusion: The authors concluded that the proposed CT system provides a semiquantitative method for assessing the relative contribution of asbestos-induced pleuropulmonary disease and smoking-related emphysema to functional impairment. They also said it is not yet clear whether less experienced readers should use it.
• Limitations the authors state:
  • The study was retrospective.
  • There was no histopathologic (tissue) proof of asbestosis.
  • The 95% confidence intervals in the explanatory equations were wide, and applying population data to individuals is problematic.
  • Variation between centers in pulmonary function testing and CT scanners would weaken the structure-function relationships.
  • It is not yet clear whether the scoring system should be widely used by less experienced radiologists and occupational physicians.

Topics

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

Medical terms in this study, explained in our Lexicon: CT Scan, Informed Consent, Pulmonary Fibrosis, Diffuse Pleural Thickening, Emphysema, Total Lung Capacity (TLC), Diffusing Capacity (DLCO).

Related studies

• Pulmonary ventilatory function in talcosis of lung — M. Kleinfeld, J. Messite, et al. (1964)
• The relation among pulmonary function, chest roentgenographic abnormalities, and smoking status in an asbestos-exposed cohort — L. Rosenstock, S. Barnhart, et al. (1988)
• Thin-section CT abnormalities and pulmonary gas exchange impairment in workers exposed to asbestos — A. Sette, J.A. Neder, 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)
• Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease — G. Lee, Y.J. Jeong, et al. (2013)
• Smoking-associated fibrosis and pulmonary asbestosis — J.R. Bledsoe, D.C. Christiani, et al. (2015)

Browse more research in Radiology, or return to medical research.