Correlation of ultra-low dose chest CT findings with physiologic measures of asbestosis

Our plain-English summary of Correlation of ultra-low dose chest CT findings with physiologic measures of asbestosis, by D. Manners, P. Wong, C. Murray, et al (European Radiology, 2017).

The study

• Authors: D. Manners, P. Wong, C. Murray, J. Teh, Y.J. Kwok, N. de Klerk, H. Alfonso, P. Franklin, A. Reid, A.W.B. Musk, F.J.H. Brims
• Journal: European Radiology
• Published: 2017;27(8):3485-3490
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: The correlation between ultra low dose computed tomography (ULDCT)-detected parenchymal lung changes and pulmonary function abnormalities is not well described. This study aimed to determine the relationship between ULDCT-detected interstitial lung disease (ILD) and measures of pulmonary function in an asbestos-exposed population.

Methods: Two thoracic radiologists independently categorised prone ULDCT scans from 143 participants for ILD appearances as absent (score 0), probable (1) or definite (2) without knowledge of asbestos exposure or lung function. Pulmonary function measures included spirometry and diffusing capacity to carbon monoxide (DLCO).

Results: Participants were 92% male with a median age of 73.0 years. CT dose index volume was between 0.6 and 1.8 mGy. Probable or definite ILD was reported in 63 (44.1%) participants. Inter-observer agreement was good (k = 0.613, p < 0.001). There was a statistically significant correlation between the ILD score and both forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) (r = -0.17, p = 0.04 and r = -0.20, p = 0.02). There was a strong correlation between ILD score and DLCO (r = -0.34, p < 0.0001).

Conclusion: Changes consistent with ILD on ULDCT correlate well with corresponding reductions in gas transfer, similar to standard CT. In asbestos-exposed populations, ULDCT may be adequate to detect radiological changes consistent with asbestosis.

Key Points: • Interobserver agreement for the ILD score using prone ULDCT is good. • Prone ULDCT appearances of ILD correlate with changes in spirometric observations. • Prone ULDCT appearances of ILD correlate strongly with changes in gas transfer. • Prone ULDCT may provide sufficient radiological evidence to inform the diagnosis of asbestosis.

In plain English

This Western Australian study examined whether lung scarring seen on ultra-low dose CT (ULDCT) chest scans matched lung function test results in people exposed to asbestos. The 143 participants came from the Asbestos Review Program. They were 92% male with a median age of 73, and most (84.5%) were former Wittenoom blue asbestos (crocidolite) workers. Each prone scan was scored by a thoracic radiologist, who did not know the person's exposure or lung function, as showing no, probable or definite interstitial lung disease (ILD). Of the 143 scans, 25 (17.5%) showed probable and 38 (26.6%) definite ILD. Higher ILD scores were associated with lower gas transfer (DLCO; r = -0.34, p less than 0.0001), which the authors called a strong correlation. Higher scores were also associated with lower FEV1 and FVC (r = -0.17 and -0.20). ILD score did not correlate with cumulative asbestos exposure. The authors concluded that ULDCT may be adequate to detect changes consistent with asbestosis. They noted there was no tissue diagnosis and no standard high-resolution CT comparison, so it is not certain the changes were asbestosis.

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: Cross-sectional analysis within a prospective observational cohort (the Asbestos Review Program), performed at one institution. Each person's CT scan was compared with lung function tests done within about one week of the scan.
• Who was studied: 143 asbestos-exposed participants in the Western Australian Asbestos Review Program. They were drawn from 906 people who had ULDCT in the program's first year (ULDCT was adopted in 2012) and were included because they had gas transfer (DLCO) measured close to the time of the scan. 131 (92.3%) were male. Median age was 73.0 years (IQR 69.9-77.0). 120 (84.5%) were blue asbestos workers, 4 (2.8%) were Wittenoom residents and 18 (12.6%) were others (railway workers, construction workers and tradesmen). 77.5% had ever smoked.
• Exposure: Asbestos exposure was mainly to crocidolite (blue asbestos) at the Wittenoom mine and town; other participants had more than 3 months' cumulative asbestos exposure. Median cumulative asbestos exposure was 5.3 fibres/ml/year (IQR 1.5-14.4). The imaging studied was prone ultra-low dose CT with a CT dose index volume of 0.6 to 1.8 mGy.
• Main results:
  • Of the 143 ULDCT scans, 80 (55.9%) showed no ILD, 25 (17.5%) probable ILD and 38 (26.6%) definite ILD.
  • Agreement between radiologists, tested on a random sample of 30 of the 143 scans that were re-read, was described as good (kappa = 0.613, p less than 0.001).
  • ILD score correlated with lower gas transfer (DLCO) in the 143 participants (r = -0.34, p less than 0.0001), which the authors described as a strong correlation.
  • Mean DLCO differed across ILD score groups: 7.9 (SD 1.9) for score 0, 6.3 (SD 2.2) for score 1 and 6.5 (SD 2.2) for score 2 mmol per min per kPa (p less than 0.0001).
  • ILD score showed a statistically significant correlation with per cent predicted FEV1 (r = -0.17, p = 0.04) and FVC (r = -0.20, p = 0.02).
  • ILD score did not correlate with cumulative asbestos exposure (r = 0.04, p = 0.69) or with FEV1/FVC ratio (r = -0.01, p = 0.88).
  • On ULDCT, pleural plaques were seen in 67.8% of the 143 participants, emphysema in 25.1% and honeycombing in 11.1%.
• The authors' conclusion: The authors concluded that, in asbestos-exposed populations, ULDCT may be adequate to detect radiological changes consistent with asbestosis, and that ILD changes on ULDCT correlate with reduced gas transfer, similar to standard CT.
• Limitations the authors state:
  • Standard high-resolution CT was not performed for comparison, because the scans were done as part of a lung cancer screening clinical service.
  • There was no tissue diagnosis, so it is not certain that the ILD seen was asbestosis.
  • The Wittenoom workers and residents may not be representative of the general asbestos-exposed population.
  • Each scan was read once by one of two radiologists; only a sample was re-read by a further radiologist.
  • The good inter-observer agreement may partly reflect the small number of observers and scans.

Topics

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

Medical terms in this study, explained in our Lexicon: Interstitial Lung Disease, Asbestos Exposure, Spirometry, Diffusing Capacity (DLCO), FEV1.

Related studies

• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)
• Ultra low dose CT screen-detected non-malignant incidental findings in the Western Australian Asbestos Review Programme — C.P. Murray, P.M. Wong, et al. (2016)
• Correlation of lung function with ultra-low-dose CT-detected lung parenchymal abnormalities: a cohort study of 1344 asbestos exposed individuals — F. Brims, E.J. Harris, et al. (2022)
• 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)
• 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)
• Low-voltage chest CT: another way to reduce the radiation dose in asbestos-exposed patients — D. Macía-Suárez, E. Sánchez-Rodríguez, et al. (2017)

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