Numbers of asbestos bodies on iron-stained tissue sections in relation to asbestos body counts in lung tissue digests

Our plain-English summary of Numbers of asbestos bodies on iron-stained tissue sections in relation to asbestos body counts in lung tissue digests, by V.L. Roggli, P.C. Pratt (Human Pathology, 1983).

The study

• Authors: V.L. Roggli, P.C. Pratt
• Journal: Human Pathology
• Published: 1983;14(4):355-61
• Cited by: 50 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Utilization of tissue digestion techniques has demonstrated the presence of large numbers of asbestos bodies within lungs of persons after occupational exposure to asbestos, and smaller numbers in the vast majority of persons with no identifiable exposure. Because of the wide variability in results of such studies among different observers, the presence of more than one asbestos body on light microscopy has been recommended recently as one of the morphologic requirements (together with peribronchiolar fibrosis) for the tissue diagnosis of asbestosis. However, data that correlate the occurrence of asbestos bodies in paraffin-embedded tissue sections with the quantification of asbestos bodies by tissue digestion techniques have not been available. The authors counted the asbestos bodies in multiple paraffin-embedded sections of lung tissues stained for iron, and compared those numbers with the asbestos body counts determined by hypochlorite digestion of wet formalin-fixed lung tissue in six cases of asbestosis or asbestos-associated neoplasia. When adjustments were made for asbestos body orientation in tissue sections, shrinkage of sections during processing, and conversion of lung volume to wet weight, the agreement between the two techniques was excellent (r = 0.98, P less than 0.001). An average of two asbestos bodies on 2 X 2 cm (4 cm2) iron-stained tissue sections 5 microns thick is equivalent to approximately 200 asbestos bodies per gram of wet fixed lung tissue.

In plain English

The authors, pathologists in Durham, North Carolina, compared two ways of counting asbestos bodies in lung tissue from six men with asbestosis or asbestos-related tumors. The cases were chosen to span the widest possible range of counts. They counted bodies on thin iron-stained microscope slides and compared those counts with counts made after dissolving lung tissue in sodium hypochlorite solution (digestion). After correcting for how the bodies lie in the slide, tissue shrinkage, and conversion of volume to weight, the two methods agreed closely (r = 0.98, P less than 0.001). By the authors' calculation, two asbestos bodies found by careful, systematic search of a whole 2 x 2 cm iron-stained section 5 micrometres thick corresponded to roughly 200 per gram of wet, fixed lung, assuming an average body length of 35 micrometres. That is ten times the laboratory's upper limit of normal. The authors stressed these were rough approximations. Counts varied widely between blocks, and whether the results apply to chrysotile-only exposure was unknown. The authors concluded iron-stained slides suit screening, but did not recommend them in place of digestion for measuring counts.

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: Methods comparison study of lung tissue from six selected cases, comparing asbestos body counts on iron-stained paraffin-embedded tissue sections with counts from hypochlorite digestion of wet formalin-fixed lung tissue
• Who was studied: Six men aged 39 to 71 with asbestosis or asbestos-related neoplasia (diagnoses included asbestosis, occult asbestosis, malignant pleural mesothelioma and squamous carcinoma of the lung), studied at Duke University and Veterans Administration Medical Centers, Durham, North Carolina. Cases were intentionally selected to include a wide range of asbestos body counts.
• Exposure: Occupational asbestos exposure: two insulators (30 and 20 years), one man who worked intermittently with asbestos insulation (34 years), two naval shipyard workers (one of whom was also an auto mechanic for 33 years), and one man whose occupation was unknown. The authors state the individuals were exposed to amphibole asbestos or to a mixture of amphiboles and chrysotile.
• Main results:
  • Across the six cases, after adjustment for asbestos body orientation, shrinkage of sections and conversion of lung volume to wet weight, counts from tissue sections and counts from digestion agreed closely (r = 0.98, P less than 0.001).
  • By the authors' calculation, two asbestos bodies identified on a single 2 x 2 cm paraffin-embedded section 5 micrometres thick and stained for iron, assuming an average asbestos body length of 35 micrometres, correspond to approximately 200 asbestos bodies per gram of wet lung tissue.
  • This equivalence is based on careful, systematic screening of the entire section on a mechanical stage at 200x magnification. With hematoxylin-eosin-stained sections or casual inspection of iron-stained sections, the authors estimated one asbestos body is probably equivalent to about 1,000 asbestos bodies by digestion.
  • The value of 200 per gram is ten times the laboratory's upper limit of normal. The normal range (0 to 20 asbestos bodies per gram) came from digestion studies of 50 consecutive autopsies of adults with no occupational asbestos exposure.
  • The authors estimated that digestion techniques are about two orders of magnitude more sensitive than a careful, systematic search of iron-stained tissue sections.
  • For a 2 x 2 mm transbronchial biopsy section containing two asbestos bodies, the corresponding digestion value would be 20,000 asbestos bodies per gram.
  • Asbestos body numbers varied considerably between tissue sections from the same case. The average coefficient of variation across the six cases was 80.4 per cent.
  • In Case 5, a section from one block contained no asbestos bodies while a section from a second block contained 15. A deeper level of the first block contained nine.
  • In Case 6, no asbestos bodies were identified on multiple hematoxylin-eosin-stained sections. They were found in four of five blocks when a single iron-stained section from each block was examined systematically.
• The authors' conclusion: The authors concluded that iron-stained sections are an appropriate qualitative screening technique for detecting asbestos bodies, but they could not recommend them as a substitute for digestion techniques for measuring tissue asbestos body counts.
• Limitations the authors state:
  • The estimates from tissue sections are only rough approximations and are substantially affected by local variation in how asbestos bodies are distributed within tissue.
  • The authors do not know whether the correlations apply to people exposed only to chrysotile.
  • The conversion formula applies only where section thickness, shrinkage, orientation and weight-to-volume values are similar to those of the authors' laboratory.
  • The calculations assumed asbestos bodies are straight, but not all of them are.
  • Recovery of asbestos bodies by digestion is probably not 100 per cent efficient.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Asbestos Body Formation, Tissue Digestion, Occupational Exposure, Fibrosis.

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• The ultrastructure of asbestos bodies from guinea-pig lungs — J.M. Davis (1964)
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• Sectioning and imaging hard mineral fibres in biological tissues — N.F. Johnson, K. Ibe (1981)
• Pulmonary fibrosis, carcinoma, and ferruginous body counts in amosite asbestos workers. A study of six cases — V.L. Roggli, S.D. Greenberg, et al. (1980)

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