Relations between vital capacity, CO diffusion capacity and computed tomographic findings of former asbestos-exposed patients: a cross-sectional study

Our plain-English summary of Relations between vital capacity, CO diffusion capacity and computed tomographic findings of former asbestos-exposed patients: a cross-sectional study, by A.M. Preisser, K. Schlemmer, R. Herold, et al (Journal of Occupational Medicine and Toxicology, 2020).

The study

• Authors: A.M. Preisser, K. Schlemmer, R. Herold, A. Laqmani, C. Terschüren, V. Harth
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2020;15:21
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Asbestos-related lung diseases are one of the leading diagnoses of the recognized occupational diseases in Germany, both in terms of their number and their socio-economic costs. The aim of this study was to determine whether pulmonary function testing (spirometry and CO diffusion measurement (DLCO)) and computed tomography of the thorax (TCT) are relevant for the early detection of asbestos-related pleural and pulmonary fibrosis and the assessment of the functional deficiency.

Methods: The records of 111 formerly asbestos-exposed workers who had been examined at the Institute for Occupational and Maritime Medicine, Hamburg, Germany, with data on spirometry, DLCO and TCT were reviewed. Workers with substantial comorbidities (cardiac, malignant, silicosis) and/or pulmonary emphysema (pulmonary hyperinflation and/or TCT findings), which, like asbestosis, can lead to a diffusion disorder were excluded. The remaining data of 41 male workers (mean 69.8 years ±6.9) were evaluated. The TCT changes were coded according to the International Classification of High-resolution Computed Tomography for Occupational and Environmental Respiratory Diseases (ICOERD) by radiologists and ICOERD-scores for pleural and pulmonary changes were determined. Correlations (ρ), Cohens κ and accuracy were calculated.

Results: In all 41 males the vital capacity (VC in % of the predicted value (% pred.)) showed only minor limitations (mean 96.5 ± 18.0%). The DLCO (in % pred.) was slightly reduced (mean 76.4 ± 16.6%; median 80.1%); the alveolar volume related value (DLCO/VA) was within reference value (mean 102 ± 22%). In the TCT of 27 workers pleural asbestos-related findings were diagnosed whereof 24 were classified as pulmonary fibrosis (only one case with honey-combing). Statistical analysis provided low correlations of VC (ρ = - 0.12) and moderate correlations of DLCO (- 0.25) with pleural plaque extension. The ICOERD-score for pulmonary fibrosis correlated low with VC (0.10) and moderate with DLCO (- 0.23); DLCO had the highest accuracy with 73.2% and Cohens κ with 0.45. DLCO/VA showed no correlations to the ICOERD-score. The newly developed score, which takes into account the diffuse pleural thickening, shows a moderate correlation with the DLCO (ρ = - 0.35, p < 0.05).

Conclusions: In formerly asbestos-exposed workers, lung function alterations and TCT findings correlated moderate, but significant using DLCO and ICOERD-score considering parenchymal ligaments, subpleural curvilinear lines, round atelectases and pleural effusion in addition to pleural plaque extension. DLCO also showed highest accuracy in regard to pulmonary findings. However, VC showed only weaker correlations although being well established for early detection. Besides TCT the determination of both lung function parameters (VC and DLCO) is mandatory for the early detection and assessment of functional deficiencies in workers formerly exposed to asbestos.

© The Author(s) 2020.

In plain English

This cross-sectional study reviewed the records of men formerly exposed to asbestos at work who were examined at an occupational medicine institute in Hamburg, Germany, between January 2013 and October 2016. Of 111 records, 41 men (average age 69.8) remained after excluding people with heart disease, cancer, silicosis, emphysema or other conditions that affect lung function. The authors compared two breathing tests, vital capacity (VC) and carbon monoxide diffusion capacity (DLCO), with chest CT scans scored by an international coding system. On CT, 27 men had pleural plaques and 18 had lung fibrosis. Average VC was 96.47% of predicted, only slightly limited. Average DLCO was reduced, at 76.35% of predicted. DLCO matched the CT finding of fibrosis better than VC did (accuracy 73.2% versus 56.1%). A new score adding other CT signs to plaque extent correlated moderately and statistically significantly with DLCO, but not significantly with VC. The authors concluded that DLCO should be measured alongside VC when checking for asbestosis. They noted that no second radiologist checked the CT readings, and that scans and breathing tests were usually not done on the same day.

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 cross-sectional study of patient records
• Who was studied: Records of 111 occupationally asbestos-exposed workers examined at the Institute for Occupational and Maritime Medicine (ZfAM), Hamburg, Germany, between January 2013 and October 2016. After exclusions (heart disease, cancer, silicosis, emphysema and other conditions affecting lung function) and quality checks, 41 men with a mean age of 69.8 years were analysed.
• Exposure: Former occupational asbestos exposure. Fiber types and products are not specified. Exposure duration in years was recorded, but it showed no statistical correlation with lung function.
• Main results:
  • In all 41 men, mean vital capacity was 96.47% of the predicted value (SD 17.96), showing slight limitation.
  • In all 41 men, mean DLCO was reduced at 76.35% of predicted (SD 16.58). DLCO/VA showed only minor deviation from the reference value.
  • On CT, 27 of the 41 men (66%) had parietal-type pleural plaques.
  • On CT, 18 men had pulmonary fibrosis, and one had honeycombing.
  • DLCO was below the lower limit of normal in 12 of 27 men (44%) with pleural plaques, compared with 3 of 14 (21%) without plaques. For indicating plaques, DLCO had an accuracy of 56.1% and VC 43.9%.
  • VC and DLCO each showed only a weak negative correlation with pleural plaque extent, and neither was statistically significant.
  • For pulmonary fibrosis on CT, DLCO had the highest accuracy at 73.2% (Cohen's kappa 0.45), and VC had an accuracy of 56.1%.
  • The extent of pulmonary fibrosis (score B) showed no correlation with VC (rho 0.10) and a moderate correlation with DLCO (rho −0.22). Neither was statistically significant.
  • The new combined score (plaque extent plus parenchymal bands, round atelectasis, subpleural curvilinear lines and pleural effusion) correlated with DLCO at rho −0.35 (p less than 0.05). Its correlation with VC (rho −0.18) was not significant.
  • A further score adding the combined score to the fibrosis score gave the highest correlation with DLCO (rho −0.41, p less than 0.01). VC showed only a weak, not significant correlation with it (rho −0.12).
  • DLCO/VA was not reduced by asbestos-related lung and pleural changes in this group.
  • Exposure duration showed no statistical correlation with changes in lung function values.
• The authors' conclusion: The authors concluded that the correlation between lung function and CT findings was strongest using DLCO together with a CT score that included parenchymal bands, subpleural curvilinear lines, round atelectasis and pleural effusion in addition to plaque extent. They concluded that DLCO should be included alongside VC in future examinations for detecting asbestosis.
• Limitations the authors state:
  • Different CT scanners were used over the 4-year period, and data sets that did not meet CT quality criteria had to be removed.
  • Smoking can affect both CT and lung function findings. Heavy smokers were few and were not analysed separately.
  • The CT scores were not checked by a second radiologist, so minor inaccuracies in the scores could occur.
  • CT and lung function tests were usually not done on the same day, and in some cases they were months apart.
  • No dependency between lung function and exposure dose was found. The authors suggest this may be due to inaccurate recording of exposures dating back decades.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Disease, Spirometry, Diffusing Capacity (DLCO), Thorax, Pulmonary Fibrosis, Silicosis, Emphysema, Pleural Plaques.

Related studies

• Restrictions of VC and DLCO in relation to asbestos-related computed tomographic findings quantified by ICOERD-based parameters — L. Ströker, K. Peldschus, et al. (2022)
• Computed tomographic findings of environmental asbestos-related malignant pleural mesothelioma — U.M. Yilmaz, G. Utkaner, et al. (1998)
• Malignant pleural mesothelioma patients' experience by gender: findings from a cross-sectional UK-national questionnaire — M. Senek, S. Robertson, et al. (2022)
• Expiratory and inspiratory forced vital capacity and one-second forced volume in asymptomatic never-smokers in Norway — A. Gulsvik, T. Tosteson, et al. (2001)
• Diffusing capacity and forced vital capacity in 5,003 asbestos-exposed workers: relationships to interstitial fibrosis (ILO profusion score) and pleural thickening — A. Miller, R. Warshaw, et al. (2013)
• Vital capacity and one-second forced expiratory volume in Australian male asbestos cement workers — L.N. Balaam, S.F. McCullagh (1975)

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