The effect of asbestos-induced pleural fibrosis on pulmonary function: quantitative evaluation

Our plain-English summary of The effect of asbestos-induced pleural fibrosis on pulmonary function: quantitative evaluation, by R. Lilis, A. Miller, J. Godbold, et al (Annals of the New York Academy of Sciences, 1991).

The study

• Authors: R. Lilis, A. Miller, J. Godbold, E. Chan, S. Benkert, I.J. Selikoff
• Journal: Annals of the New York Academy of Sciences
• Published: 1991;643:162-8
• Type of article: Review
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004939).

Summary of the article

The authors proposed an integrative index of pleural fibrosis (INDEX) and used it to examine how asbestos-related pleural fibrosis relates to pulmonary function. The index combined all pleural features recorded under the 1980 ILO International Classification of Radiographs of Pneumoconioses: chest wall pleural fibrosis in profile (extent and width), pleura face on, diaphragmatic plaque and pleural calcification. It was scored for each hemithorax, with a maximum total of 40. INDEX values were calculated for 1,584 asbestos insulation workers with long-term exposure, most for more than 30 years. All were members of a cohort of 17,800 men in the United States and Canada who were examined between July 1981 and November 1983, 30 or more years after starting work. The examination included histories, chest X-rays and spirometry. Pleural fibrosis was present in 1,185 men (75%); 82.3% of these cases were circumscribed and 17.7% diffuse. Years since first exposure was the only variable significantly correlated with the index. High INDEX values (≥12) were more common when interstitial fibrosis was also present (8% versus 1.5%). In multiple regression, the index was significantly associated with lower forced vital capacity (FVC % predicted), independently of the profusion of small opacities, smoking and years since first exposure. In the circumscribed subgroup, the inverse relationship was significant (p < .0001). In the diffuse subgroup, the presence of diffuse fibrosis lowered FVC even at low index values. The authors concluded that extensive circumscribed pleural fibrosis has a negative, restrictive effect on pulmonary function.

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In plain English

The authors proposed a single score, the integrative index of pleural fibrosis (INDEX). It combines all the features of pleural fibrosis (scarring of the lining around the lungs) that are recorded on chest X-rays under the 1980 ILO classification. They calculated the score for 1,584 asbestos insulation workers in the United States and Canada, most of whom had been exposed for more than 30 years. Pleural fibrosis was present in 1,185 of them (75%). In regression analyses, the pleural index was a significant factor in lower forced vital capacity (FVC, a breathing test), independent of the small opacities on X-ray that indicate lung tissue scarring. Years since first exposure and smoking also lowered FVC. The index remained significant in workers with pleural changes only. Among workers with circumscribed (localized) pleural fibrosis, FVC fell as the index rose (p less than 0.0001). In workers with diffuse pleural fibrosis, the size of the index did not seem to matter significantly, but diffuse fibrosis lowered FVC even at low index values. The authors concluded that extensive circumscribed pleural fibrosis has a negative, restrictive effect on lung function.

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: Proposal of a scoring index for pleural fibrosis on chest X-rays, applied in a cross-sectional analysis of medical examination data (chest X-rays and spirometry) from members of a prospectively followed cohort
• Who was studied: 1,584 asbestos insulation workers drawn from a cohort of 17,800 men in the United States and Canada. The cohort was established on 1 January 1967. Members who had reached 30 years from the start of work and accepted an invitation were examined between July 1981 and November 1983.
• Exposure: Long-term occupational asbestos exposure as insulation workers, the majority for more than 30 years. Fiber types were not specified.
• Main results:
  • Pleural fibrosis was present in 1,185 of the 1,584 workers (75%).
  • Age, years exposed, years since first exposure and smoking were tested. Of these, years since first exposure was the only variable significantly correlated with the pleural index.
  • High index values were more common in workers who also had interstitial pulmonary fibrosis visible on X-ray than in those without it: 8% versus 1.5%.
  • In multiple regression analysis of FVC (% predicted), the pleural index was a significant variable contributing to lower FVC, independent of the profusion of small opacities.
  • Years since first exposure and cigarette smoking (pack-years) also had significant negative effects on FVC.
  • In the subgroup with pleural abnormalities only (no small opacities on X-ray), the pleural index was also a significant variable for FVC.
  • Mean FVC (% predicted) decreased gradually as the index increased. At each index value, the decrease was more marked when parenchymal abnormalities were also present.
  • Among workers with pleural fibrosis, 82.3% had circumscribed pleural fibrosis and 17.7% had diffuse pleural fibrosis.
  • In the circumscribed pleural fibrosis subgroup, there was a significant inverse relationship between FVC and the index (p less than .0001). This was after adjustment for duration since onset of exposure, smoking and profusion of small opacities.
  • In the diffuse pleural fibrosis subgroup, the size of the index did not seem to significantly affect FVC. However, the presence of diffuse pleural fibrosis lowered FVC even at low index values.
  • Smoking (current and ex-smokers) had an additional lowering effect on FVC in the subgroup with pleural changes only.
  • In the subgroup with parenchymal changes only (n = 389), all persons with small-opacity profusion of grade 2/1 or higher had a smoking history.
• The authors' conclusion: The authors concluded that pleural fibrosis significantly lowered forced vital capacity, independent of small opacities. They also concluded that circumscribed pleural fibrosis, when extensive, has a negative, restrictive effect on pulmonary function.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Pleura, Pleural Calcification, Hemithorax, Insulator, Chest X-Ray, Spirometry, Interstitial Fibrosis.

Related studies

• Comparative quantitative evaluation of pleural fibrosis and its effects on pulmonary function in two large asbestos-exposed occupational groups--insulators and sheet metal workers — R. Lilis, A. Miller, et al. (1992)
• Pulmonary function and pleural fibrosis: quantitative relationships with an integrative index of pleural abnormalities — R. Lilis, A. Miller, et al. (1991)
• Relation of spirometric function to radiographic interstitial fibrosis in two large workforces exposed to asbestos: an evaluation of the ILO profusion score — A. Miller, R. Lilis, et al. (1996)
• Pulmonary fibrosis in asbestos insulation workers with lung cancer: a radiological and histopathological evaluation — H.M. Kipen, R. Lilis, et al. (1987)
• Restrictive lung function and asbestos-induced pleural fibrosis. A quantitative approach — D.A. Schwartz, J.R. Galvin, et al. (1993)
• Radiographic abnormalities in asbestos insulators: effects of duration from onset of exposure and smoking. Relationships of dyspnea with parenchymal and pleural fibrosis — R. Lilis, A. Miller, et al. (1991)

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