Pleural plaques and asbestosis: dose- and time-response relationships based on HRCT data

Our plain-English summary of Pleural plaques and asbestosis: dose- and time-response relationships based on HRCT data, by C. Paris, S. Thierry, P. Brochard, et al (The European Respiratory Journal, 2009).

The study

• Authors: C. Paris, S. Thierry, P. Brochard, M. Letourneux, E. Schorle, A. Stoufflet, J. Ameille, F. Conso, J.C. Pairon, National APEXS Members
• Journal: The European Respiratory Journal
• Published: 2009;34(1):72-9
• Cited by: 76 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Most studies on asbestos-related diseases are based on chest radiographs, and dose-response relationships are still controversial. The aim of this study was to describe the most relevant parameters of asbestos exposure linked to pleural plaques and asbestosis diagnosed by high-resolution computed tomography (HRCT). A large screening programme including systematic HRCT examinations was organised from 2003 to 2005 in France for formerly asbestos-exposed workers. The time since first exposure (TSFE), level, duration and cumulative exposure to asbestos were used in adjusted unconditional logistic regression to model the relationships of the two diseases. Analysis of a population of 5,545 subjects demonstrated that TSFE (p<0.0001) and cumulative exposure (p = 0.02) (or level, depending on the models used), were independently associated with the frequency of pleural plaques. Only cumulative exposure (p<0.0001) or level of exposure (p = 0.02) were significantly associated with asbestosis. All trend tests were significant for these parameters. To date and to our knowledge, this study is the largest programme based on HRCT for the screening of asbestos-exposed subjects. Both time-response and dose-response relationships were demonstrated for pleural plaques, while only dose-response relationships were demonstrated for asbestosis. These parameters must be included in the definition of high-risk populations for HRCT-based screening programmes.

In plain English

This study analysed APEXS, a French screening programme (2003 to 2005) in which retired or unemployed workers formerly exposed to asbestos volunteered for high-resolution CT (HRCT) chest scans. Exposure was estimated from job questionnaires using a job-exposure matrix. The article does not say which fiber types these workers were exposed to. Of 5,545 subjects analysed, HRCT showed pleural plaques in 15.9% (882), asbestosis in 6.8% (375) and diffuse pleural thickening in 0.7% (37). In adjusted models, pleural plaques were independently associated with time since first exposure (odds ratio 2.01, 95% confidence interval 1.60 to 2.54, highest versus lowest quartile). They were also associated with the cumulative exposure index (odds ratio 1.49, 95% confidence interval 1.18 to 1.89, same quartile comparison) or, in a second model, with exposure level. Asbestosis was associated only with the cumulative exposure index or exposure level, associations the authors described as weak. Duration of exposure was not significant in the models. The authors noted that volunteers may not be representative and exposure estimates may be inaccurate. They concluded that time and dose parameters must be included in defining high-risk groups for screening.

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 data from a large HRCT-based screening programme for asbestos-related disease, using stepwise unconditional logistic regression to relate exposure parameters to pleural plaques and asbestosis
• Who was studied: 5,545 formerly asbestos-exposed workers, all unemployed or retired and covered by French National Health Insurance, who volunteered for the APEXS screening programme in four French regions (Aquitaine, Rhône-Alpes, Lower Normandy, Upper Normandy) between October 2003 and December 2005. Females, nonexposed subjects and those with missing reports or incomplete data were excluded. Mean age was 63.5 years.
• Exposure: Occupational asbestos exposure. The article does not specify fiber types for the APEXS population. Exposure was assessed from a job questionnaire using a simplified job-exposure matrix. Level of exposure was classed as high, moderate, low (passive) or nil. A cumulative exposure index was calculated as level (3, 2, 1, 0) multiplied by exposure duration in years. Time since first exposure and duration were also analysed. 80.1% (4,443) were rated as having a high level of exposure. Mean time since first exposure was 41.9 years and mean duration was 27.4 years. Main jobs included machinery mechanics, plumbers and pipe fitters, motor-vehicle mechanics, bricklayers, electricians and insulation workers.
• Main results:
  • Among all 5,545 subjects, HRCT showed pleural plaques in 15.9% (882), asbestosis in 6.8% (375) and diffuse pleural thickening in 0.7% (37).
  • Pleural plaques, adjusted model I: the highest versus lowest quartile of time since first exposure had an odds ratio of 2.01 (95% CI 1.60–2.54).
  • Pleural plaques, adjusted model I: the highest versus lowest quartile of the cumulative exposure index had an odds ratio of 1.49 (95% CI 1.18–1.89).
  • Pleural plaques, adjusted model II: high versus weak intensity of exposure had an odds ratio of 2.89 (95% CI 1.51–5.52).
  • Duration of exposure was not significant in the multivariate models and was removed from them.
  • Asbestosis: only the cumulative exposure index (model I) and level of exposure (model II) remained significant after adjustment for smoking status. Time since first exposure did not remain significant.
  • Asbestosis, adjusted odds ratios by cumulative exposure index versus the first quartile: 2.04 (1.44–2.88) for the second quartile, 1.93 (1.36–2.74) for the third and 2.17 (1.54–3.05) for the fourth. By intensity versus weak: moderate 0.75 (0.37–1.53) and high 1.20 (0.62–2.30), with p = 0.02.
  • The authors described the correlations between cumulative exposure (or level) and asbestosis as weak. They suggested this may reflect the low prevalence of asbestosis in the cohort.
  • Higher prevalences of pleural plaques and asbestosis were seen in insulation workers, handlers and shipyard repair workers. For example, pleural plaques were found in 50 of 136 insulation workers (36.8%) and in 50 of 139 subjects in ship building and repairs (36.0%).
• The authors' conclusion: The authors concluded that time since first exposure was independently associated with pleural plaques, and that dose parameters (cumulative exposure or level) were associated with both pleural plaques and asbestosis. They concluded that these time and dose parameters must be included in defining high-risk populations for future screening programmes.
• Limitations the authors state:
  • Only volunteers were included, so the study population may not be representative of the general population.
  • CT findings were rated from radiologists' reports. In a review of a random subsample of 1,600 scans, the pleural plaque models were confirmed, but the asbestosis models were not significant because there were too few cases.
  • The accuracy of the exposure parameters, particularly the cumulative exposure index, may be questionable.
  • There were numerous missing data, especially for smoking status and body mass index.
  • There is uncertainty in the choice of statistical models. The authors re-analysed the data with a power model and found no differences in which variables were significant.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Plaques, High-Resolution CT (HRCT), Chest X-Ray, Dose-response relationship, Asbestos Exposure, Cumulative Exposure.

Related studies

• Relationships between asbestos exposure and pleural plaques: dose and time effects using fractional polynomials — M. Menant, I. Benlala, et al. (2024)
• Inter-reader agreement in HRCT detection of pleural plaques and asbestosis in participants with previous occupational exposure to asbestos — F. Laurent, C. Paris, et al. (2014)
• Do asbestos-related pleural plaques on HRCT scans cause restrictive impairment in the absence of pulmonary fibrosis? — B. Clin, C. Paris, et al. (2011)
• Asbestos exposure and benign asbestos diseases in 772 formerly exposed workers: dose-response relationships — G. Mastrangelo, M.N. Ballarin, et al. (2009)
• Asbestos-related pleural diseases: dimensional criteria are not appropriate to differentiate diffuse pleural thickening from pleural plaques — J. Ameille, M. Matrat, et al. (2004)
• Asbestos exposure, pleural plaques, and the risk of death from lung cancer — J.C. Pairon, P. Andujar, et al. (2014)

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