A retrospective study on radiological findings of diffuse pleural thickening with benign asbestos pleural effusion in Japanese cases

Our plain-English summary of A retrospective study on radiological findings of diffuse pleural thickening with benign asbestos pleural effusion in Japanese cases, by T. Kishimoto, K. Kato, K. Ashizawa, et al (Industrial Health, 2022).

The study

• Authors: T. Kishimoto, K. Kato, K. Ashizawa, Y. Kurihara, T. Tokuyama, F. Sakai
• Journal: Industrial Health
• Published: 2022;60(5):429-435
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The requirement for compensation for diffuse pleural thickening in benign asbestos pleural effusion include five computed tomography findings of organized pleural effusion: [1] heterogeneity in the pleural effusion, [2] declined chest capacity, [3] "crow's feet" sign at the pleura, [4] immobilization of effusion volume, and [5] air in the effusion. Pleural effusion is diagnosed as organized, immobilized, and in the state of diffuse pleural thickening if at least three of these items are fulfilled, ([1] and [3] compulsory + one of the remaining items). This retrospective study investigated whether the requirement to confirm no organized pleural effusion changes after a follow-up of >3 months were available for cases fulfilling three of the five items; i.e., the confirmation of only [2] with [1] and [3]. Of 302 cases recognized by the Japanese laws, 105 cases with diffuse pleural thickening with organized effusion were enrolled. The number of subjects who fulfilled the diagnostic requirement for organized pleural effusion was confirmed. Eight subjects had a full score of 5 points, 82 subjects scored 4 points, and only 15 subjects scored 3 points. Furthermore, no changes were observed in the organized pleural effusion volume after a follow-up of >3 months.

In plain English

This retrospective study from Japan reviewed chest CT scans of men with diffuse pleural thickening after benign asbestos pleural effusion, fluid around the lung linked to asbestos. Since 2017, a Japanese relief law has used five CT findings to decide whether this fluid has become organized and fixed. At least three findings must be present, and two of them are compulsory. Of 302 people recognized under Japanese compensation and relief laws, the authors studied 105 men, aged 53 to 93, with organized pleural effusion and CT follow-up. They excluded 57 cases without pleural effusion and 140 without CT follow-up. All 302 had more than 3 years of occupational asbestos exposure. Eight men showed all five findings, 82 showed four and 15 showed three. Both compulsory findings were seen in all 105. Most of the 15 with three findings showed no change in fluid volume over 7 to 12 months. Of 102 men tested, 95 (93.1%) had percent vital capacity below 60%. The authors concluded the 3-month follow-up rule was "considered available". They noted a prospective study would be ideal.

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: Retrospective study of chest X-ray and CT images of cases recognized for compensation or relief
• Who was studied: 105 men in Japan, aged 53–93 at diagnosis (mean 72.8, median 73), with diffuse pleural thickening and organized pleural effusion. They were drawn from 302 cases recognized under the Worker's Accident Compensation Law and the Act on Asbestos Health Damage Relief (January 2020).
• Exposure: Occupational asbestos exposure of more than 3 years, which was a requirement for recognition. The article gives no fiber types, products or jobs.
• Main results:
  • Of the 302 recognized cases, 105 with organized pleural effusion who could be followed on chest CT were included. The authors excluded 57 cases without pleural effusion and 140 that could not be followed on CT.
  • Of the 105 subjects, 8 (7.6%) scored all 5 CT findings, 82 (78.1%) scored 4 and 15 (14.3%) scored 3
  • Heterogeneity in the pleural effusion and the "crow's feet" sign were both seen in all 105 subjects
  • Declined chest capacity was seen in 93 subjects (88.6%)
  • Most of the 15 subjects who scored 3 points showed no change in pleural effusion volume during 7–12 months of follow-up
  • Confirming organization took less than 3 months in 9.5% of subjects
  • Of the 102 subjects whose %VC was measured, 95 (93.1%) had a %VC below 60%
  • After about 3 months of follow-up, no subject whose %VC had dropped below 60% rose above 60% again
  • Pleural plaque was present in 92.9% of subjects. Pulmonary fibrosis was present in 32.6%, but no typical asbestosis was observed.
• The authors' conclusion: The authors concluded that the 3-month follow-up after confirmation of pleural effusion organization was "considered available".
• Limitations the authors state:
  • The observation period should ideally be set in a prospective study, but follow-up from benign asbestos pleural effusion to diffuse pleural thickening was possible in only a limited number of cases
  • Benign asbestos pleural effusion is not a target disease under the relief Act, which makes it difficult to confirm
  • In a retrospective study, chest CT images were not always taken together with chest X-rays

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: Diffuse Pleural Thickening, Benign Asbestos Pleural Effusion, Pleural Effusion, Pleura.

Related studies

• Asbestos-related diffuse pleural thickening — N. Fujimoto, K. Kato, et al. (2014)
• Retrospective investigation on diagnostic process for benign asbestos pleural effusion (BAPE) using checklist — T. Kishimoto, N. Fujimoto, et al. (2020)
• Pleural irregularities and mediastinal pleural involvement in early stages of malignant pleural mesothelioma and benign asbestos pleural effusion — K. Kato, K. Gemba, et al. (2016)
• Development, radiological zone patterns, and importance of diffuse pleural thickening in relation to occupational exposure to asbestos — H. Bohlig, A. Calavrezos (1987)
• Clinical Investigation of Benign Asbestos Pleural Effusion — N. Fujimoto, K. Gemba, et al. (2015)
• Diffuse pleural thickening following heart failure-related pleural effusions in an asbestos exposed patient — M. Evison, P. Barber (2015)

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