Carbon monoxide and nitric oxide diffusion capacity of formerly exposed asbestos workers with high-resolution computed tomography in a cross-sectional study

Our plain-English summary of Carbon monoxide and nitric oxide diffusion capacity of formerly exposed asbestos workers with high-resolution computed tomography in a cross-sectional study, by J. Krabbe, D.J. Reimers, N. Otte, et al (Scientific Reports, 2025).

The study

• Authors: J. Krabbe, D.J. Reimers, N. Otte, P. Doukas, T. Dirrichs, T. Radtke, H. Dressel, T. Kraus
• Journal: Scientific Reports
• Published: 2025;15(1):15380
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos exposure can induce pulmonary fibrosis known as asbestosis, and pleural thickening, as well as various cancers. Although lung diffusion capacity (DL) including nitric oxide (NO) is assumed to be more sensitive than carbon monoxide (CO), its added value in assessment of pneumoconiosis has not been investigated yet. 371 formerly exposed workers visiting the outpatient clinic for assessment including pulmonary function testing with DL and low-dose high resolution computed tomography between 2018 and 2021 were included. Subgroups were formed depending on findings in low-dose high resolution computed tomography classified according to ICOERD. Receiver operating characteristic curve (ROC) analysis revealed some diagnostic accuracy for DLNO (AUC = 0.73; 95% confidence interval 0.64-0.82) and DLCO (AUC = 0.70; 95% confidence interval 0.60-0.79) regarding asbestosis, but not per unit alveolar volume. DLCO and DLNO correlated strongly with a decreasing score of irregular opacities according to ICOERD (ρDLCO = - 0.87, ρDLNO = - 0.85) but DLNO was also susceptible to emphysema. Although tendencies of a more sensitive detection of diffusion capacity impairment were observed, DLNO was not clearly superior to DLCO in assessment of asbestosis. Based on our findings and considering the lack of availability of DLNO in clinical routine, DLNO does not seem to have added value for clinical assessment of formerly asbestos exposed workers. Future studies should further investigate DLNO including healthy controls and confounders such as emphysema and smoking.

© 2025. The Author(s).

In plain English

This cross-sectional study looked at 371 men with past asbestos exposure seen at an outpatient clinic in Aachen, Germany, from September 2018 to February 2021. Each had breathing tests, two gas transfer measures (DLCO, using carbon monoxide, and DLNO, using nitric oxide), and low-dose high resolution CT scans. The scans sorted the men into groups such as no findings, pleural findings only, asbestosis, and emphysema. For identifying asbestosis, defined as a score of at least 4 for irregular opacities in both lower lung fields, DLNO had an area under the curve of 0.73 (95% confidence interval 0.64 to 0.82) and DLCO 0.70 (0.60 to 0.79). The versions adjusted for lung volume were not significantly different from chance. Both measures fell as the CT score for irregular opacities rose, but DLNO was also affected by emphysema. Only 22 men met that asbestosis definition, 17 more had scores of 2 to 3, and there were no healthy unexposed controls. The authors concluded DLNO was not clearly superior to DLCO and does not seem to add value in assessing formerly asbestos-exposed workers.

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 of routine clinical data from an outpatient clinic
• Who was studied: 371 male patients with documented former asbestos exposure, mean age 70.7 years (range 53 to 85), seen at the RWTH Aachen University Hospital occupational medicine outpatient clinic in Germany from September 2018 to February 2021. They came for an acknowledged asbestos-related occupational disease, an assessment for an occupational disease, or a surveillance program. Patients with lung cancer, mesothelioma, other cancers or collagen disease were excluded. CT-based groups were: no findings 82, only pleural findings 97, asbestosis score 2 to 3 (17), asbestosis score at least 4 (22), only emphysema 40, and mixed findings 113.
• Exposure: Former asbestos exposure. Fiber types and specific jobs or products are not named. Median exposure duration was 20 years (range 0.1 to 151; data for 330 patients). Median cumulative exposure was 21 fibre years (range 0.1 to 755; data for 192 patients).
• Main results:
  • For the ROC analysis, asbestosis was defined as a score of at least 4 for bilateral irregular opacities in the lower lung fields. For detecting asbestosis on this definition, DLNO had the highest area under the curve: AUC 0.73 (95% CI 0.64 to 0.82), with sensitivity 77.27% and specificity 67.34%. DLCO had AUC 0.70 (95% CI 0.60 to 0.79), with sensitivity 68.18% and specificity 70.77%.
  • The lung-volume-adjusted measures were not significantly different from chance for detecting asbestosis. DLCO/VA had AUC 0.59 (0.47 to 0.70) and DLNO/VA had AUC 0.62 (0.51 to 0.72).
  • When specificity was set to at least 90%, sensitivity for asbestosis was around 14% for both DLCO and DLNO.
  • Compared with the no-findings group, DLCO was reduced in the asbestosis (score at least 4), emphysema and mixed-findings groups. Mean DLCO %pred was 74.85 in the asbestosis score at least 4 group versus 90.98 in the no-findings group. Mean DLNO %pred was 59.56 versus 79.11.
  • DLCO and DLNO correlated strongly with a decreasing score of irregular opacities (rho minus 0.87 for DLCO, minus 0.85 for DLNO). Excluding patients with emphysema did not significantly change the DLCO correlation (z = 0.855, p = 0.196). For DLNO the correlation coefficients were slightly lower after this exclusion (z = 5.003, p less than 0.001).
  • In multiple linear regression (n = 190), DLCO and DLNO were significantly associated with the extent of asbestosis and with emphysema. They were not significantly associated with pack years, cumulative asbestos exposure in fibre years, or pleural thickening. The authors described the effect sizes as minimal and lacking clinical relevance.
  • Overall, spirometry values (FVC, FEV1 and FEV1/FVC) were above the lower limit of normal.
• The authors' conclusion: The authors concluded that DLNO was not clearly superior to DLCO for detecting asbestosis and assessing its severity. They also noted that DLNO was susceptible to interference from emphysema. Given this and DLNO's limited availability in routine care, they concluded it does not seem to add value in the clinical assessment of formerly asbestos-exposed workers.
• Limitations the authors state:
  • Few patients had severe asbestosis. Of the 22 with a score of at least 4, more than half had a score of exactly 4.
  • Healthier patients may have been selected, because people with high exposure and asbestosis may have died or been unable to attend the clinic.
  • There were no healthy non-exposed controls, so slight impairments without visible CT changes could not be identified.
  • The sample may reflect a selective patient population, which limits representativeness and generalizability.
  • The regression models explained only 14% (DLCO) and 16% (DLNO) of the variability, so unmeasured factors likely play a role.
  • Smokers and pack-years were unevenly distributed across groups.
  • The mixed-findings subgroup combined different conditions, so no specific conclusion could be drawn for it.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Pulmonary Fibrosis, Pleural Thickening, Pneumoconiosis, confidence interval, Diffusing Capacity (DLCO), Emphysema.

Related studies

• Relations between vital capacity, CO diffusion capacity and computed tomographic findings of former asbestos-exposed patients: a cross-sectional study — A.M. Preisser, K. Schlemmer, et al. (2020)
• High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs — C.A. Staples, G. Gamsu, et al. (1989)
• Increased alveolar nitric oxide concentration and high levels of leukotriene B(4) and 8-isoprostane in exhaled breath condensate in patients with asbestosis — H. Lehtonen, P. Oksa, et al. (2007)
• Are the knowledge of non-malignant asbestos-related diseases and lung function impairment differentially associated with psychological well-being? A cross-sectional study in formerly asbestos-exposed workers in Germany — J. Lang, M.K. Felten, et al. (2019)
• 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)
• Effects of asbestos and smoking on gas diffusion in people exposed to crocidolite — H.S. Alfonso, L. Fritschi, et al. (2005)

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