Radiological surveillance of formerly asbestos-exposed power industry workers: rates and risk factors of benign changes on chest X-ray and MDCT

Our plain-English summary of Radiological surveillance of formerly asbestos-exposed power industry workers: rates and risk factors of benign changes on chest X-ray and MDCT, by C. Eisenhawer, M.K. Felten, M. Tamm, et al (Journal of Occupational Medicine and Toxicology, 2014).

The study

• Authors: C. Eisenhawer, M.K. Felten, M. Tamm, M. Das, T. Kraus
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2014;9:18
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: To determine the prevalence of asbestos-related changes on chest X-ray (CXR) and low-dose multidetector-row CT (MDCT) of the thorax in a cohort of formerly asbestos-exposed power industry workers and to assess the importance of common risk factors associated with specific radiological changes.

Methods: To assess the influence of selected risk factors (age, time since first exposure, exposure duration, cumulative exposure and pack years) on typical asbestos-related radiographic changes, we employed multiple logistic regression and receiver operating characteristic (ROC) analysis.

Results: On CXR, pleural changes and asbestosis were strongly associated with age, years since first exposure and exposure duration. The MDCT results showed an association between asbestosis and age and between plaques and exposure duration, years since first exposure and cumulative exposure. Parenchymal changes on CXR and MDCT, and diffuse pleural thickening on CXR were both associated with smoking. Using a cut-off of 55 years for age, 17 years for exposure duration and 28 years for latency, benign radiological changes in the cohort with CXR could be predicted with a sensitivity of 82.0% for all of the three variables and a specificity of 47.4%, 39.0% and 40.6%, respectively.

Conclusions: Participants aged 55 years and older and those with an asbestos exposure of at least 17 years or 28 years since first exposure should be seen as having an increased risk of abnormal radiological findings. For implementing a more focused approach the routine use of low-dose MDCT rather than CXR at least for initial examinations would be justified.

In plain English

This study analysed chest imaging of German power industry workers formerly exposed to asbestos. Of 5622 reporting exposure, 3257 with complete data were analysed. Of these, 3061 had X-rays; 196 judged higher risk had low-dose CT. On X-ray, 13.8% showed changes: plaques 7.9%, diffuse pleural thickening 5.9%, signs of asbestosis 1.0%. On CT, 60.2% showed changes: plaques 57.1% and findings classified as signs of asbestosis 20.4%, which the authors judged probably nonspecific, smoking-related changes rather than asbestosis. The authors attributed the higher CT rates to risk-based selection and CT's better performance. On X-ray, changes were associated mainly with age, time since first exposure and exposure duration; plaques also with cumulative exposure. The authors suspected smoking-related changes were also misread as asbestosis on X-ray. Cut-offs of age 55, 17 years of exposure, or 28 years since first exposure each detected 82% of workers with X-ray changes, but specificities were 47.4%, 39.0% and 40.6%, so over half without changes also met each cut-off. The authors said these cut-offs need validation. They concluded these groups should be prioritised and low-dose CT justified for initial examinations.

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: Analysis of radiological surveillance data (chest X-ray or low-dose multidetector-row CT) from a cohort of asbestos-exposed workers, using multiple logistic regression and ROC analysis
• Who was studied: Current and former workers of a major German electrical power provider, most stationed at one of six lignite- or coal-fired plants, examined between March 2002 and end of 2006. Of 5622 who reported asbestos exposure, 4446 were examined. 3257 with complete data were analysed: 3061 by chest X-ray and 196 by low-dose MDCT. The MDCT group was preselected as higher risk using a score based on exposure duration, age and smoking.
• Exposure: Occupational asbestos exposure in power plant work. Examples include revisions of steam turbines (59% of 5284 with job data), removal of asbestos lagging (21%), spraying of asbestos pulp (4%), and handling of asbestos-containing gaskets, packings and mats. Cumulative exposure in fibre years was estimated from self-reported job titles and tasks using workplace airborne fibre monitoring data. Median cumulative exposure was 4.9 fibre years in the X-ray group and 18.0 in the MDCT group. Fibre types were not specified.
• Main results:
  • Chest X-ray group (n = 3061): any changes in 422 (13.8%), signs of asbestosis in 32 (1.0%), plaques in 242 (7.9%), diffuse pleural thickening in 180 (5.9%).
  • MDCT group (n = 196): any changes in 118 (60.2%), findings classified as signs of asbestosis in 40 (20.4%), plaques in 112 (57.1%). The authors explained the higher rates by the higher-risk preselection of this group and the better performance of MDCT. They also judged the parenchymal changes detected to be probably nonspecific, smoking-related changes rather than asbestosis.
  • Chest X-ray group: plaques were mainly associated with age (odds ratio 1.84 per 10 years, 95% CI 1.61-2.10), time since first exposure and exposure duration. After adjusting for age, plaques were also associated with cumulative exposure when comparing 25 or more fibre years with 1 or fewer (odds ratio 1.64, 95% CI 1.11-2.42).
  • Chest X-ray group: signs of asbestosis were associated with all risk factors, but with an inverted effect of fibre years (odds ratio about 0.3 for more than 1 and less than 25 versus 1 or fewer fibre years). The authors judged this not plausible. Diffuse pleural thickening was associated with all risk factors, including pack years, except cumulative exposure.
  • MDCT group: signs of asbestosis were associated only with age and pack years. Plaques were associated with time since first exposure, exposure duration, and fibre years (25 or more versus 1 or fewer, in the model adjusting for age).
  • Chest X-ray group, predicting any benign changes with sensitivity fixed at a minimum of 80%: the cut-offs were age 55 years (AUC 0.694), time since first exposure 28 years (AUC 0.666) and exposure duration 17 years (AUC 0.660). At 82.0% sensitivity, specificity was 47.4% for age, 39.0% for exposure duration and 40.6% for time since first exposure (given as 47%, 39% and 41% in the Results). For the MDCT group, no acceptable cut-offs were found (AUC below 0.6).
• The authors' conclusion: The authors concluded that asbestos-related radiological changes were strongly associated with the time-related factors age, time since first exposure and exposure duration, with a weak association between pleural lesions and cumulative exposure. They concluded that X-ray surveillance should first prioritise people aged 55 or older, then those with at least 17 years of exposure or at least 28 years since first exposure. They also concluded that a more focused approach would justify routine low-dose MDCT rather than X-ray for initial examination.
• Limitations the authors state:
  • The inverse association between asbestosis and fibre years on X-ray was probably due to smoking-related changes being misread as asbestosis. The low number of asbestosis cases on X-ray was another likely reason.
  • The MDCT group was small.
  • Given the low diagnostic threshold and the association with pack years, parenchymal changes on MDCT were probably not asbestosis but nonspecific, probably smoking-related changes.
  • X-ray performs poorly in distinguishing the two pleural lesions, so diffuse pleural thickening may have been underestimated.
  • The cut-offs did not achieve excellent discrimination. They are based on this particular X-ray cohort and need validation in further studies.
  • Many fibre-year values were missing, which reduced the number analysed. Sensitivity analyses without cumulative exposure changed results only marginally.

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Thorax, Cumulative Exposure, Diffuse Pleural Thickening, Latency, Asbestos Exposure.

Related studies

• Changes of mesothelin and osteopontin levels over time in formerly asbestos-exposed power industry workers — M.K. Felten, K. Khatab, et al. (2014)
• Is it useful to combine sputum cytology and low-dose spiral computed tomography for early detection of lung cancer in formerly asbestos-exposed power industry workers? — M.K. Felten, L. Knoll, et al. (2014)
• Retrospective exposure assessment to airborne asbestos among power industry workers — M.K. Felten, L. Knoll, et al. (2010)
• Asbestos exposure and benign asbestos diseases in 772 formerly exposed workers: dose-response relationships — G. Mastrangelo, M.N. Ballarin, et al. (2009)
• UK Naval Dockyards Asbestosis Study: radiological methods in the surveillance of workers exposed to asbestos — G. Sheers, C.E. Rossiter, et al. (1978)
• Cancer mortality in a surveillance cohort of German males formerly exposed to asbestos — B. Pesch, D. Taeger, et al. (2010)

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