Comment on "HRCT/CT and Associated Spirometric Effects of Low Libby Amphibole Asbestos Exposure" by Lockey et al (2015)

Our plain-English summary of Comment on "HRCT/CT and Associated Spirometric Effects of Low Libby Amphibole Asbestos Exposure" by Lockey et al (2015), by G. Tao, K. Zu, L.E. Kerper, et al (Journal of Occupational and Environmental Medicine, 2015).

The study

• Authors: G. Tao, K. Zu, L.E. Kerper, J.E. Goodman
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2015;57(7):e80
• Type of article: Letter, Comment
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This is a letter to the editor, not a new study. Its authors, employed by the consulting firm Gradient, wrote it with financial support from W.R. Grace & Co. The letter criticized a cross-sectional study by Lockey et al of workers exposed to Libby amphibole asbestos. That study had reported that workers with localized pleural thickening (LPT), but no other lung abnormalities, had a statistically significant mean decrease of 6.1% in percent-predicted forced vital capacity. The letter's authors argued that this association was more likely a result of methodological limitations than a sign of causation. They noted that 10 subjects (6.5%) had spirometry up to 6 to 7 years before their CT scans. They also noted that five participants were classified as having diffuse pleural thickening from chest X-rays, even though CT did not show it. They argued that cumulative fiber exposure was a potential confounder that should have been adjusted for. They also questioned whether 70 never-smokers had been dropped when pack-years were log-transformed. The authors concluded that the Lockey study does not establish whether LPT is a causal factor for lung function decrements.

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: Letter to the editor commenting on another published study (no new data)
• Who was studied: No study population of its own; the letter discusses the Lockey et al cross-sectional analysis of a group of workers exposed to Libby amphibole asbestos (total sample size given as n = 126)
• Exposure: Libby amphibole asbestos (as studied by Lockey et al)
• Main results:
  • The letter restated Lockey et al's finding that workers with localized pleural thickening only had a statistically significant mean decrease of 6.1% in percent-predicted FVC but no significant decrement in FEV1, and argued this was more likely due to methodological limitations than causality
  • The letter noted that in the Lockey study spirometry was done within 24 hours of HRCT/CT for 137 (84.4%) subjects, within 3 years for 14 (9.1%), and up to 6 to 7 years before HRCT/CT for 10 (6.5%). It said sensitivity analyses should have been done.
  • The letter objected that five participants were classified as having diffuse pleural thickening based on chest radiographs, although HRCT/CT did not identify it, and were excluded from the LPT lung function analysis
  • The letter argued that cumulative fiber exposure was a potential confounder that should have been adjusted for in the LPT analyses
  • The letter questioned the use of log-transformed pack-years, given 70 never-smokers. Its authors assumed those subjects were excluded from the analyses.
• The authors' conclusion: The authors contended that the Lockey et al study does not establish whether localized pleural thickening is a causal factor for lung function decrements

Topics

Medical terms in this study, explained in our Lexicon: High-Resolution CT (HRCT), Libby amphiboles, Asbestos Exposure.

Related studies

• HRCT/CT and associated spirometric effects of low Libby amphibole asbestos exposure — J.E. Lockey, K. Dunning, et al. (2015)
• Comment on "Exposure-response modeling of non-cancer effects in humans exposed to Libby Amphibole Asbestos; update" by Benson et al. (2015) — J.E. Goodman, K. Zu, et al. (2016)
• Low levels of exposure to libby amphibole asbestos and localized pleural thickening — K.Y. Christensen, T.F. Bateson, et al. (2013)
• Libby Amphibole Disease: Pulmonary Function and CT Abnormalities in Vermiculite Miners — A. Miller, J. Szeinuk, et al. (2018)
• Pulmonary inflammatory and fibrotic responses in Fischer 344 rats after intratracheal instillation exposure to Libby amphibole — D.J. Padilla-Carlin, M.C. Schladweiler, et al. (2011)
• Comparative long-term toxicity of Libby amphibole and amosite asbestos in rats after single or multiple intratracheal exposures — J.M. Cyphert, D.J. Carlin, et al. (2015)

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