Clinical and HRCT screening of heavily asbestos-exposed workers

Our plain-English summary of Clinical and HRCT screening of heavily asbestos-exposed workers, by T. Vierikko, R. Järvenpää, P. Toivio, et al (International Archives of Occupational and Environmental Health, 2010).

The study

• Authors: T. Vierikko, R. Järvenpää, P. Toivio, J. Uitti, P. Oksa, T. Lindholm, T. Vehmas
• Journal: International Archives of Occupational and Environmental Health
• Published: 2010;83(1):47-54
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To characterize asbestosis today and to clarify the indications for high-resolution computed tomography (HRCT) in the surveillance of heavily exposed workers.

Methods: Six hundred and twenty-seven workers were screened and HRCT findings were classified and divided in two groups: pulmonary fibrosis (n = 86) and no fibrosis (n = 541).

Results: Most (65/86 = 76%) of the detected fibrosis cases were mild. The magnitude of asbestos exposure showed an unexpected inverse relation with fibrosis. In multivariate analyses, age, forced expiratory volume in 1 s/forced vital capacity ratio, and poor diffusing capacity were associated with HRCT fibrosis, but asbestos exposure was not.

Conclusions: Asbestosis seems to be characterized by mild fibrosis today even in heavily exposed workers. To avoid radiation exposure in HRCT, age and lung function data may be used only to a limited extent to select imaging candidates. Selection and recollection biases may distort the relation between asbestos exposure and fibrosis.

In plain English

This cross-sectional study from Finland screened 627 men with heavy past work exposure to asbestos, mostly construction workers, using high-resolution CT (HRCT), lung function tests, blood tests and questionnaires. HRCT changes consistent with lung fibrosis (class 2 or more on a Finnish scale) were found in 86 of the 627 men (13.7%). Most were mild: 65 were in class 2 and only 2 in class 4, described as advanced. Men with fibrosis were older and, in a simple comparison, had a lower average asbestos exposure index (64.5 versus 79.2). After adjustment for other factors, older age, lower diffusing capacity and a higher FEV1/FVC ratio were associated with fibrosis. The exposure index was not significantly related. The authors concluded that asbestosis today seems to be characterized by mild fibrosis even in heavily exposed workers, and that age and lung function data can be used only to a limited extent to choose who gets HRCT. They noted that the study design, forgotten exposures and selection of healthier workers may have distorted the link between exposure and fibrosis.

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 screening study using HRCT, questionnaires, clinical examination, blood tests and lung function tests
• Who was studied: 627 men (mean age 64.4) in Finland, from the Helsinki, Tampere and Turku areas. They came from an earlier 1990–1992 asbestos screening program and from occupational medicine clinics in Helsinki and Tampere. Of 758 invited, 633 attended. The 6 women who attended were excluded.
• Exposure: Occupational asbestos exposure, estimated from a questionnaire as a cumulative asbestos exposure index (mean 77.2, range 4–286). Mean exposure duration was 19.2 years and mean latency 41.7 years. 566 (90.3%) were construction workers, of whom 264 were plumbers. Fiber types were not reported.
• Main results:
  • HRCT fibrosis (Finnish class 2 or more) was found in 86 (13.7%) of the 627 workers.
  • Of the 86 fibrosis cases, 65 (75.6%) were class 2 and 9 were class 2.5, both described as mild. Only 2 were in class 4, described as advanced.
  • In unadjusted comparison, the mean asbestos exposure index was lower in the fibrosis group (64.5) than in the no-fibrosis group (79.2), P = 0.009. This was an inverse relation.
  • In the adjusted (multivariate) analysis, older age was associated with HRCT fibrosis: OR 1.144 (95% CI 1.085–1.206), P less than 0.001.
  • In the adjusted analysis, lower diffusing capacity (DLCO, percent of predicted) was associated with fibrosis: OR 0.969 (95% CI 0.954–0.984). DLCO/VA showed OR 0.970 (95% CI 0.954–0.988).
  • In the adjusted analysis, a higher FEV1/FVC ratio was associated with fibrosis: OR 1.036 (95% CI 1.003–1.070).
  • In the adjusted analysis, the asbestos exposure index (OR 0.997, 95% CI 0.991–1.004, P = 0.433), latency and symptoms were not significantly related to fibrosis.
  • In crude comparisons, dyspnea (P = 0.028) and persistent cough (P = 0.043) were associated with fibrosis. These associations were not found after adjustment.
  • Laboratory tests (hemoglobin, CRP, hematocrit, ESR, total cholesterol) showed no significant association with fibrosis.
  • Emphysema prevalence did not differ significantly between the fibrosis group (25/86, 29.1%) and the no-fibrosis group (117/541, 21.6%).
  • In age-adjusted analysis, the asbestos exposure index was inversely related to wheezing.
  • The Helsinki radiologist pair found more fibrosis cases than the Tampere pair.
• The authors' conclusion: The authors concluded that asbestosis seems to be characterized by mild fibrosis today even in heavily exposed workers. They also concluded that age and lung function data may be used only to a limited extent to select candidates for HRCT, and that selection and recollection biases may distort the relation between exposure and fibrosis.
• Limitations the authors state:
  • The study was cross-sectional with no follow-up, so the actual development of fibrosis could not be determined.
  • The exposure index was based only on questionnaire answers. Older workers may have forgotten past exposures (recollection bias).
  • Selection bias: more seriously ill workers may have died, changed jobs and been lost from follow-up, or been too ill to take part.
  • A healthy worker effect may explain the apparent inverse relation between exposure and fibrosis.
  • Group differences in lung function cannot be applied directly to individual patients. Measurements often fell within normal limits, and the odds ratios between groups were minor.

Topics

Medical terms in this study, explained in our Lexicon: High-Resolution CT (HRCT), Pulmonary Fibrosis, Fibrosis, Asbestos Exposure, Diffusing Capacity (DLCO).

Related studies

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• The effects of secondhand smoke exposure on HRCT findings among asbestos-exposed workers — T. Vierikko, R. Järvenpää, et al. (2008)
• HRCT/CT and associated spirometric effects of low Libby amphibole asbestos exposure — J.E. Lockey, K. Dunning, et al. (2015)
• 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)
• Comment on "HRCT/CT and Associated Spirometric Effects of Low Libby Amphibole Asbestos Exposure" by Lockey et al (2015) — G. Tao, K. Zu, et al. (2015)
• Psychological impact of computed tomography screening for lung cancer and occupational pulmonary disease among asbestos-exposed workers — T. Vierikko, S. Kivistö, et al. (2009)

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