Fissural thickening and exposure to asbestos: occurrence, determinants, and functional impact

Our plain-English summary of Fissural thickening and exposure to asbestos: occurrence, determinants, and functional impact, by J. Zejda, P. Ernst (American Journal of Industrial Medicine, 1991).

The study

• Authors: J. Zejda, P. Ernst
• Journal: American Journal of Industrial Medicine
• Published: 1991;20(6):785-93
• Cited by: 4 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. 004910).

Abstract

The occurrence and determinants of thickened interlobar fissures were assessed in 147 insulators, in order to test the hypothesis that radiographic abnormalities in minor (FMN) and/or major (FMJ) interlobar fissures are associated with restrictive respiratory impairment, which may reflect early parenchymal lung fibrosis. According to the diagnostic criteria developed, definite interlobar thickening was found in 33 (FMN) and in 73 (FMJ) men, and was frequently associated with the presence of classical asbestos pleural disease, though not parenchymal abnormality. Multivariate analyses did not demonstrate any association between either FMN or FMJ and lung function. Such an association, however, was found in the case of the usual asbestos-related pleural change. These findings suggest that fissural thickening seen on chest radiography represents a component of asbestos pleural disease and not asbestosis.

In plain English

This study examined 147 male construction insulators from Local 58 of the insulators' union in the Montreal area. All were 50 or younger and none was compensated for asbestosis. The authors tested whether thickened interlobar fissures on chest X-rays, which had been proposed as an early sign of asbestosis, were linked to lower lung function. Using the mean of two readers' scores, minor fissure thickening was found in 33 men and major fissure thickening in 73. Classical pleural abnormalities were found in 58 men, and small irregular opacities of category 1/0 or greater in 12. Men with fissural thickening were older and had more chest wall pleural thickening, but a similar prevalence of small irregular opacities. In unadjusted comparisons they had lower FVC. After adjusting for age, height, smoking, opacities and pleural thickening, fissural thickening showed no significant relationship with lung function. Only peripheral pleural thickening was associated with lower FEV1 and FVC. The authors concluded that fissural thickening represents a component of asbestos pleural disease and not asbestosis. They noted that their scoring scale was not fully validated.

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 study comparing chest X-ray findings with lung function tests (spirometry and diffusing capacity) in one group of currently working insulators
• Who was studied: 147 male construction insulators, members of Local 58 of the International Union of Frost and Heat Insulation and Asbestos Workers, Montreal area. All were in the trade at examination, aged 50 or less, and not compensated for asbestosis. Of 644 members, 246 were eligible and 215 agreed to take part. Complete data were available for 147 (60% of eligible). Mean age 36.9 years (range 18-50). The dates of examination are not stated.
• Exposure: Asbestos exposure in the insulating trade, measured as duration of exposure: mean 28.2 thousand hours (range 0.37-453.9). The authors describe the workforce as having approximately 15-35 years of exposure. Fiber types are not specified.
• Main results:
  • Thickening of the minor fissure (score 3 or more on the 8-point scale, mean of two readers) was observed in 33 of the 147 men.
  • Thickening of the major fissure was observed in 73 of the 147 subjects. It was associated with older age, longer exposure, a higher pleural disease score and lower FVC.
  • By individual reader, thickened minor fissures were reported in 25% (reader A) or 30.7% (reader B) of subjects. The corresponding figures for major fissures were 53.9% and 54.6%.
  • Small irregular opacities of category 1/0 or greater were found in 12 subjects, and classical pleural abnormalities in 58 subjects.
  • Subjects with and without fissural thickening had a similar prevalence of small irregular opacities (lung parenchymal changes).
  • After adjusting for age, height, smoking in pack-years, small irregular opacities and pleural thickening, there was no significant relationship between any lung function measure and fissural thickening. This held whether the two fissures were considered together or separately.
  • The only X-ray abnormality significantly associated with lower lung function was peripheral pleural thickening, which was associated with lower FEV1 and FVC but not DLCO (diffusing capacity).
  • Agreement between the two readers on fissural thickening was 66.3% (kappa 0.499, 'good') for the minor fissure and 55.7% (kappa 0.355, 'fair') for the major fissure.
• The authors' conclusion: The authors concluded that fissural thickening is a not infrequent X-ray finding in asbestos-exposed subjects. In their view it represents a component of asbestos pleural disease and not asbestosis, and any effect on lung function can be explained by the associated pleural disease.
• Limitations the authors state:
  • Full validation of the fissure scoring scale would require within-reader variability measurements and comparison between teams. The authors say this is impossible without standardized radiographs showing fissural thickening.
  • Measuring thickening as small as 0.5 mm on a chest X-ray may be difficult.
  • Because both fissures were scored on the same scale, the higher number of definite major fissure changes may have resulted from magnification inherent in the lateral chest X-ray view.

Topics

Medical terms in this study, explained in our Lexicon: Insulator, Fibrosis, Asbestos-Related Pleural Disease.

Related studies

• Visceral pleural thickening in asbestos exposure: the occurrence and implications of thickened interlobar fissures — S.D. Rockoff, E. Kagan, et al. (1987)
• Mineralogical and exposure determinants of pulmonary fibrosis among Québec chrysotile miners and millers — A. Nayebzadeh, B.W. Case, et al. (2006)
• Impact of body mass index on the detection of radiographic localized pleural thickening — T.C. Larson, A. Franzblau, et al. (2014)
• Focal dependent pleural thickening at MDCT: pleural lesion or functional abnormality? — M. Claude-Desroches, G. Bierry, et al. (2012)
• Spiroergometric parameters at maximal exercise testing assessed functional respiratory impairment in asbestos-induced fibrosis — J. Schneider, R. Arhelger, et al. (2014)
• Low levels of exposure to libby amphibole asbestos and localized pleural thickening — K.Y. Christensen, T.F. Bateson, et al. (2013)

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