Correlation of lung function with ultra-low-dose CT-detected lung parenchymal abnormalities: a cohort study of 1344 asbestos exposed individuals

Our plain-English summary of Correlation of lung function with ultra-low-dose CT-detected lung parenchymal abnormalities: a cohort study of 1344 asbestos exposed individuals, by F. Brims, E.J. Harris, C. Kumarasamy, et al (BMJ Open Respiratory Research, 2022).

The study

• Authors: F. Brims, E.J. Harris, C. Kumarasamy, A. Ringuet, B. Adler, P. Franklin, N. de Klerk, B. Musk, C. Murray
• Journal: BMJ Open Respiratory Research
• Published: 2022;9(1)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Deliberate exposure to medical ionising radiation should be as low as reasonably practicable but the reduction of radiation from CT should be balanced against diagnostic image quality. The ability of ultra-low-dose CT (uLDCT: similar radiation to chest X-ray) to demonstrate low contrast abnormalities (emphysema and interstitial lung abnormality (ILA)) is unclear.The aim of this cross-sectional study was to analyse the lung parenchymal findings from uLDCT scans against physiological measures of respiratory function.

Methods: WA Asbestos Review Programme participants were eligible if they had an uLDCT scan and lung function assessment between Janary and December 2018. All scans were performed using a single CT machine and reported using a standardised, semiquantitative synoptic report which includes emphysema and linear fibrosis (ILA) scores.

Results: Of 1344 participants, median (IQR) age was 72.0 (65.0-78.0) years, the majority were males (84.9%) with mixed occupational asbestos exposure (68.1%). There were 721 (53.6%) with no abnormality, 158 (11.8%) with emphysema, 465 (34.6%) with ILA. Mean radiation dose was 0.12 mSv. There was statistically significant between group differences for all physiological parameters of lung function compared with controls. For instance, the emphysema score significantly correlated with obstructive forced expiratory volume in 1 s (FEV1)/forced vital capacity ratio (r=0.512), per cent predicted FEV1 (r=0.24) and lower diffusion of carbon monoxide (DLCO) (r=0.337). Multivariate modelling demonstrated that increasing age, emphysema and fibrosis scores predicted reduced DLCO (adjusted R2=0.30).

Discussion: uLDCT-detected parenchymal lung abnormalities correlate strongly with significant changes on lung function testing suggesting the observed CT abnormalities are of physiological and clinical significance.

© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

In plain English

This cross-sectional study looked at 1344 people in the Western Australia Asbestos Review Programme who had an ultra-low-dose chest CT scan and lung function tests in 2018. Most were men (84.9%), and the median age was 72.0 years. Most participants (68.1%) reported mixed occupational exposure to mixed asbestos fibre types. Others were former miners or residents of Wittenoom, where crocidolite (blue asbestos) was mined. The mean radiation dose was 0.12 mSv. Scans showed no lung tissue abnormality in 721 people (53.6%), emphysema in 158 (11.8%) and linear fibrosis in 465 (34.6%). The 94 people (7.0%) who had both were counted in both groups. Both groups differed significantly from people with no abnormality on all lung function measures. Higher emphysema and fibrosis scores correlated with lower gas transfer (DLCO). In a model, older age and higher emphysema and fibrosis scores predicted lower DLCO. Estimated asbestos exposure was not statistically significant (p=0.072). The authors concluded that these scan findings correlate strongly with meaningful lung function changes. They noted that scans were not double-read or compared with standard-dose CT or chest X-ray.

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 study comparing ultra-low-dose CT findings with lung function tests (the title calls it a cohort study)
• Who was studied: 1344 participants in the Western Australia Asbestos Review Programme who had an annual review in 2018 with paired ultra-low-dose CT and lung function. Median age was 72.0 (IQR 65.0 to 78.0) and 1141 (84.9%) were male.
• Exposure: Asbestos exposure: 915 (68.1%) had mixed occupational, mixed-fibre exposure. The rest were ex-Wittenoom residents or ex-Wittenoom miners; the programme was originally set up for crocidolite workers at the Wittenoom mine. Cumulative exposure was estimated with an Australian job-exposure matrix or with Wittenoom dust measurements. The imaging studied was ultra-low-dose CT.
• Main results:
  • Mean radiation dose of the scans was 0.12 (SD 0.03) mSv.
  • Whole cohort: 721 (53.6%) had no CT lung tissue abnormality, 158 (11.8%) had emphysema and 465 (34.6%) had linear fibrosis. 94 (7.0%) had both and were included in both groups.
  • Pleural plaque was present in 802 of 1344 (59.7%).
  • Both the emphysema group and the fibrosis group showed statistically significant differences on all lung function measures compared with the no-abnormality group.
  • Emphysema score correlated with lower DLCO (r=0.337) and linear fibrosis score correlated with lower DLCO (r=0.362), both p less than 0.0005.
  • Emphysema score correlated with the FEV1/FVC ratio (r=0.512, p less than 0.0005).
  • In multiple regression, increasing age, emphysema score and fibrosis score predicted reduced DLCO (adjusted R2=0.30).
  • In the same model, estimated asbestos exposure was not statistically significant: B -0.08, 95% CI -0.16 to 0.01, p=0.072.
  • Cumulative asbestos exposure in the fibrosis group was not statistically different from the no-abnormality group (p=0.959).
  • Among the 1344 participants there were four confirmed lung cancers and no mesothelioma.
• The authors' conclusion: The authors concluded that lung tissue abnormalities detected on ultra-low-dose CT correlate strongly with physiologically significant changes on lung function testing. They contended that a move away from routine chest X-ray towards ultra-low-dose CT may be indicated.
• Limitations the authors state:
  • Scans were not read by two readers with formal consensus methods.
  • Ultra-low-dose CT images were not compared with standard-dose CT as a gold standard, or with chest X-ray.
  • On generalisability, the authors noted that the population was mainly an ageing blue-collar workforce.

Topics

Medical terms in this study, explained in our Lexicon: Cohort Study, Chest X-Ray, Emphysema, Interstitial, Fibrosis, Asbestos Exposure, FEV1, Diffusing Capacity (DLCO).

Related studies

• Correlation of ultra-low dose chest CT findings with physiologic measures of asbestosis — D. Manners, P. Wong, et al. (2017)
• 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)
• 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)
• Low dose CT detected interstitial lung abnormalities in a population with low asbestos exposure — E.J.A. Harris, K.P. Lim, et al. (2021)
• Chest pain in asbestos-exposed individuals with benign pleural and parenchymal disease — S. Mukherjee, N. de Klerk, et al. (2000)
• 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)

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