Relationship between pleural plaques and biomarkers of cumulative asbestos dose. A necropsy study

Our plain-English summary of Relationship between pleural plaques and biomarkers of cumulative asbestos dose. A necropsy study, by P.G. Barbieri, D. Consonni, A. Somigliana (La Medicina del Lavoro, 2019).

The study

• Authors: P.G. Barbieri, D. Consonni, A. Somigliana
• Journal: La Medicina del Lavoro
• Published: 2019;110(5):353-362
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The relationship between pleural plaques and cumulative asbestos exposure is controversial.

Objectives: To evaluate the relationship between lung asbestos bodies (AB) and fibres (AF) and plaques presence and extension.

Methods: In a necropsy series of shipyard workers with asbestos-related diseases, we measured counts (per g of dry lung tissue) of AB (thousands) and AF>1 µm (millions). Pleural plaques were classified into three extension grades. We fitted univariate and multivariable linear (dependent variables: AB and AF, log10 transformed) and multinomial (dependent variable: plaques grade) regression models.

Results: We analysed 124 subjects, 13 without plaques 20 with grade 1, 69 with grade 2, and 22 with grade 3 plaques. Geometric means (GM) of AB were 10.6, 23.3, 126, and 140 in the four groups respectively (P=0.0001). GMs for AF (mostly amphiboles) were 1.2, 1.4, 7.3, and 12.9 (P=0.0001). AB and AF were strongly correlated (r=0.81). The likelihood of no plaques and grade 1 plaques decreased with increasing AB and AF doses, with a corresponding increase of grade 2 and 3 plaques. Plaque presence and extension was also associated with histologically verified asbestosis (P<0.001).

Conclusions: Our study showed a strong positive relationship between pleural plaque presence and extension and both lung asbestos burden and asbestosis.

In plain English

This autopsy-based study examined 124 former workers of a large shipyard in Monfalcone, North-East Italy (117 men, 7 women), who died of asbestos-related diseases, most often mesothelioma or lung cancer. Lung analyses were done between 2008 and 2017. Pathologists graded pleural plaques at autopsy without knowing lung asbestos levels. Thirteen people had no plaques, 20 had grade 1, 69 had grade 2 and 22 had grade 3, the most extensive. The researchers counted asbestos bodies and asbestos fibres, mostly amphiboles, in lung tissue. Geometric mean asbestos body concentrations in the four groups were 10.6, 23.3, 126 and 140 thousand per gram of dry lung. For fibres they were 1.2, 1.4, 7.3 and 12.9 million per gram. After adjustment, people with grade 2 or 3 plaques had about 5 to 11 times the levels of people without plaques. The no-plaque and grade 1 groups differed only slightly. Histologically verified asbestosis was more frequent with more extensive plaques. The authors concluded that plaque extent might serve as an approximate index of lung asbestos levels. They named the small number of people without plaques as the main limitation.

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: Necropsy (autopsy) study analysing pleural plaque grade against lung asbestos body and fibre counts, drawn from an existing necropsy series
• Who was studied: 124 former workers of a large shipyard in Monfalcone, North-East Italy, who died from asbestos-related diseases (66 mesothelioma, 48 lung cancer, 9 asbestosis, 1 isolated plaques); 117 men and 7 women. Of 142 subjects retrieved for 2008-2017, 18 were excluded because plaque extension could not be determined.
• Exposure: Occupational asbestos exposure in shipyard work (mean length of exposure 22.1 years), measured as lung asbestos bodies (thousands per g dry lung) and asbestos fibres longer than 1 µm (millions per g dry lung). Fibres were counted as amphibole (amosite and crocidolite together), chrysotile, and the non-commercial amphiboles tremolite and actinolite. In 70 (56.5%) subjects all fibres were amphiboles, and in only 13 (10.5%) amphiboles made up less than 80%.
• Main results:
  • Of the 124 subjects, 13 (10.5%) had no pleural plaques, 20 (16.1%) had grade 1, 69 (55.7%) had grade 2 and 22 (17.7%) had grade 3 plaques.
  • Geometric mean concentrations of asbestos bodies (thousands per g dry lung) were 10.6 (no plaques), 23.3 (grade 1), 126 (grade 2) and 140 (grade 3), P=0.0001. Geometric mean concentrations of asbestos fibres (millions per g dry lung) were 1.2, 1.4, 7.3 and 12.9 in the same groups, P=0.0001.
  • Adjusted geometric mean ratios compared with subjects without plaques were as follows. For asbestos bodies: 1.76 (90% CI 0.57-5.46) for grade 1, 8.83 (3.23-24.2) for grade 2 and 11.3 (3.74-34.1) for grade 3. For asbestos fibres: 1.07 (0.39-2.89) for grade 1, 5.49 (2.26-13.3) for grade 2 and 10.2 (3.83-26.9) for grade 3. P-trend was less than 0.001 for both.
  • Subjects without plaques had asbestos body and fibre concentrations only slightly lower than subjects with grade 1 plaques.
  • For a ten-fold increase in asbestos bodies and asbestos fibres respectively, compared with no plaques, the crude prevalence odds ratios were 1.55 and 1.31 for grade 1, 4.53 and 5.84 for grade 2, and 4.89 and 9.00 for grade 3. Adjusted results were substantially similar.
  • In the adjusted model, the predicted probability of having no plaques fell from 40% at the lowest asbestos body dose to 0.4% at the highest dose.
  • Asbestos body and fibre counts were strongly correlated with each other.
  • Histologically verified asbestosis was found in 44 of 124 subjects (35.5%). By plaque group it was present in 3 of 13 without plaques (23.1%), 0 of 20 with grade 1, 28 of 69 with grade 2 (40.6%) and 13 of 22 with grade 3 (59.1%), P less than 0.001.
  • Age, duration of exposure, and time since first and last exposure showed little or no correlation with asbestos body or fibre levels.
• The authors' conclusion: The authors concluded that there was a strong relationship between the presence and extension of pleural plaques and lung asbestos burden. They wrote that plaque extension might serve as an approximate index of asbestos body and fibre concentrations, and that their findings contrast with the American Thoracic Society statement that there is no relationship between plaques and cumulative exposure.
• Limitations the authors state:
  • The authors identified the small number of subjects without plaques as the main limitation.
  • Information on tobacco smoking was not available. The authors argued this was not a limitation, citing literature that smoking does little or nothing to modify asbestos burden.

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: Pleural Plaques, Biomarker, Autopsy, Asbestos Exposure, Asbestos Bodies, Amphibole Group.

Related studies

• Pleural plaques and asbestosis: dose- and time-response relationships based on HRCT data — C. Paris, S. Thierry, et al. (2009)
• Relationships between asbestos exposure and pleural plaques: dose and time effects using fractional polynomials — M. Menant, I. Benlala, et al. (2024)
• Pleural plaques and exposure to mineral fibres in a male urban necropsy population — A. Karjalainen, P.J. Karhunen, et al. (1994)
• 'Black Spots' and hyaline pleural plaques on the parietal pleura of 150 urban necropsy cases — K. Mitchev, P. Dumortier, et al. (2002)
• Pleural plaques as risk indicators for malignant pleural mesothelioma: a necropsy-based study — C. Bianchi, A. Brollo, et al. (1997)
• Asbestos bodies and pleural plaques in human lungs at necropsy — I. Hägerstrand, B. Seifert (1973)

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