The usefulness of computed tomography in detecting asbestos-related pleural abnormalities in people who had indeterminate chest radiographs: the Libby, MT, experience

Our plain-English summary of The usefulness of computed tomography in detecting asbestos-related pleural abnormalities in people who had indeterminate chest radiographs: the Libby, MT, experience, by O.I. Muravov, W.E. Kaye, M. Lewin, et al (International Journal of Hygiene and Environmental Health, 2005).

The study

• Authors: O.I. Muravov, W.E. Kaye, M. Lewin, Z. Berkowitz, J.A. Lybarger, S.S. Campolucci, J.E. Parker
• Journal: International Journal of Hygiene and Environmental Health
• Published: 2005;208(1-2):87-99
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This epidemiological study was conducted to determine whether high-resolution computed tomography (HRCT) is useful to screen for pulmonary abnormalities in people exposed to vermiculite containing asbestos. During June-September 2001, we evaluated HRCT of 353 people in Libby, MT, who had been exposed to asbestiform minerals associated with vermiculite. Of these, 334 participants of the summer 2000 medical testing program underwent HRCT of the chest at St. John's Lutheran Hospital and 19 eligible people who recently had undergone an HRCT scan at the same facility and under the same testing protocol allowed the study reviewers to use that scan. All 353 study participants were former vermiculite mine/mill workers (n = 55), their household contacts (n = 99), and people exposed to vermiculite through recreational or other activities (n = 199). Participants' 2000 medical testing results indicated only one of the three B-reader chest radiograph reviewers had reported a pleural abnormality (indeterminate chest radiograph). Three expert computer tomography (CT) scan evaluators reviewed the HRCT scans and identified pleural abnormalities in 98 (27.8%) of the 353 participants whose previous chest radiographs were classified indeterminate. Of these 98 people, 69 (70.4%) were either former vermiculite mine/mill workers or household contacts, and 40 (40.8%) showed pleural calcification on HRCT. Thirty out of the 40 people with pleural calcification reported having no occupational exposure to either Libby vermiculite or asbestos. Our findings indicate that low-dose HRCT can be considered for screening certain former vermiculite mine/mill workers and their household contacts who have indeterminate chest radiographs and may be useful for diagnosing a suspicious finding on a chest radiograph, particularly in a high-risk person.

In plain English

In 2001 the authors evaluated HRCT (high-resolution CT) chest scans of 353 Libby, Montana adults: 334 new scans and 19 recent scans taken under the same protocol. Their chest X-rays in a 2000 testing program were indeterminate: only one of three expert readers reported a pleural abnormality. They comprised 55 former vermiculite mine/mill workers, 99 household contacts, and 199 people exposed through recreational or other activities. Libby vermiculite ore contains tremolite and actinolite asbestos. HRCT showed pleural abnormalities in 98 people (27.8%): 47.5% of household contacts, 40.0% of former workers and 14.6% of the recreational group. Compared with the recreational group, adjusted odds ratios were 3.96 (95% confidence interval 1.86 to 8.41) for former workers and 6.32 (3.47 to 11.54) for household contacts. Of 40 people with pleural calcification, 30 reported no occupational vermiculite or asbestos exposure. The authors concluded HRCT might be a useful screening tool for former workers and household contacts with indeterminate X-rays. They noted a 7 to 11 month gap between X-ray and scan, 157 refusals, and no standard system for classifying HRCT findings.

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: Epidemiological screening study (cross-sectional) testing whether HRCT is useful for people whose earlier chest radiographs were indeterminate
• Who was studied: 353 adults with indeterminate chest radiographs in the 2000 Libby medical testing program, which tested 6149 people; 886 of them were eligible for this study. Of the 353, 334 underwent HRCT for the study at St. John's Lutheran Hospital. The other 19 had recently been scanned at the same facility under the same protocol and allowed the reviewers to use that scan. The group was 55 former vermiculite mine/mill workers, 99 household contacts of former workers, and 199 people exposed through recreational or other activities. The response rate was 66.4% (353 of 532).
• Exposure: Vermiculite from Zonolite Mountain near Libby, containing tremolite asbestos, actinolite asbestos and other amphibole asbestiform minerals. Participants were grouped by highest reported exposure: work with W.R. Grace/Zonolite or another vermiculite job; household contact with a former W.R. Grace/Zonolite worker; or recreational and other activities.
• Main results:
  • HRCT found pleural abnormalities in 98 of the 353 participants (27.8%), all of whom had indeterminate chest radiographs.
  • Household contacts of former vermiculite workers had the highest prevalence of pleural abnormalities: 47 of 99 (47.5%).
  • Former workers: 22 of 55 (40.0%) had pleural abnormalities on HRCT (Table 1).
  • People recreationally exposed: 29 of 199 (14.6%) had pleural abnormalities on HRCT (Table 1).
  • Compared with the recreationally exposed group, the adjusted odds ratio for any pleural abnormality was 3.96 (95% CI 1.86 to 8.41) for former workers and 6.32 (95% CI 3.47 to 11.54) for household contacts.
  • 40 of the 98 people with positive HRCT scans (40.8%) showed pleural calcification.
  • 30 of the 40 participants with pleural calcification (75.0%) reported no occupational exposure to vermiculite or asbestos.
  • Of the 98 people with pleural abnormalities on HRCT, 43 (43.9%) did not report cough, shortness of breath or pleuritic chest pain.
  • For 14 participants, HRCT showed extrapleural/subcostal fat and no pleural abnormality, which explained their indeterminate chest radiographs.
• The authors' conclusion: The authors concluded that HRCT might be a useful screening tool for former vermiculite workers and their household contacts who have indeterminate chest radiographs. They also concluded that HRCT may help confirm a suspicious chest radiograph finding in a high-risk person, and may detect asbestos-related pleural abnormalities before symptoms begin.
• Limitations the authors state:
  • Seven to 11 months passed between the 2000 chest radiographs and the HRCT, so some abnormalities may have developed in that interval.
  • 157 eligible people refused to take part, and 60 of them were former workers or household contacts. More recreationally exposed people were therefore tested, and the authors stated that the prevalence of abnormalities might otherwise have been greater.
  • No HRCT scans were done on people with entirely negative or entirely positive chest radiographs. The authors therefore could not calculate sensitivity, specificity or predictive values for chest radiography.
  • No widely accepted standard system exists for classifying asbestos-related findings on HRCT. Readings can therefore depend on the observer, which makes comparisons within and between studies difficult.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Chest X-Ray, High-Resolution CT (HRCT), vermiculite, Asbestiform, B-Reader, Pleural Calcification, Occupational Exposure, Libby Vermiculite.

Related studies

• Diagnostic Performance of Ultra-Low-Dose Computed Tomography for Detecting Asbestos-Related Pleuropulmonary Diseases: Prospective Study in a Screening Setting — M. Schaal, F. Severac, et al. (2016)
• Radiographic abnormalities and exposure to asbestos-contaminated vermiculite in the community of Libby, Montana, USA — L.A. Peipins, M. Lewin, et al. (2003)
• Computed tomography of asbestos-related pleural abnormalities — M. Tiitola, L. Kivisaari, et al. (2002)
• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)
• Libby Amphibole Disease: Pulmonary Function and CT Abnormalities in Vermiculite Miners — A. Miller, J. Szeinuk, et al. (2018)
• Agreement between chest radiography and high-resolution computed tomography in diagnosing dust-related interstitial lung fibrosis — R.R. Tiwari (2015)

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