Interobserver variability in analysis of asbestos fibres and asbestos bodies in human lung tissue

Our plain-English summary of Interobserver variability in analysis of asbestos fibres and asbestos bodies in human lung tissue, by F. Roberts, J.L. Mackinnon, L. Cherrie, et al (Medicine, Science, and the Law, 2004).

The study

• Authors: F. Roberts, J.L. Mackinnon, L. Cherrie, R.A. Burnett, C.M. Harper
• Journal: Medicine, Science, and the Law
• Published: 2004;44(2):151-9
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Two different methods of quantifying asbestos fibre burden were assessed and the counts obtained were compared with semi-quantitative asbestos body counts in corresponding tissue sections. Comparison of the two methods found significantly different asbestos fibre counts between specimens. Each technique showed wide limits of agreement for reproducibility and interobserver variability as assessed by Bland-Altman plots, such that a repeated count could not necessarily be expected to lie within the same exposure category. Asbestos body counts in tissue sections were reproducible with good correlation between observers. Asbestos body and asbestos fibre counts showed correlation in some samples but not others. Counting of asbestos bodies is a valuable screening technique as the finding of asbestos bodies is accepted as a marker of significant asbestos exposure. When no asbestos bodies are identified asbestos fibres estimations may be useful in proving asbestos exposure. Different techniques are not interchangeable and each laboratory should establish a background range from unexposed individuals.

In plain English

This laboratory study from Glasgow compared two light-microscope methods (called method A and method B) for counting asbestos fibres in lung tissue. The lung samples came from autopsy cases with a history of asbestos exposure and related disease. One of the 20 samples was excluded for heavy carbon content. Two observers, who did not know where each sample came from, counted each sample twice by each method. Three pathologists graded asbestos bodies in one tissue section per case as none, few or many. The two methods gave significantly different counts, and method A gave lower results. Repeat counts and counts by different observers varied widely. For observer 1, a repeat method A count could be expected to lie between 786% above and 96% below the first count. The authors said a repeated count might not fall in the same exposure category. Asbestos bodies were found in 14 samples, and all three pathologists agreed on 12 samples (63%). Both fibre methods gave counts that were inappropriately low in seven samples compared with the asbestos bodies seen. The authors concluded that counting asbestos bodies is a valuable screening technique and that the fibre-counting methods are not interchangeable.

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: Laboratory method-comparison study measuring repeatability and interobserver variability of two light-microscope asbestos fibre counting methods and of asbestos body grading in tissue sections
• Who was studied: 20 formalin-fixed lung tissue samples from autopsy cases with a history of asbestos exposure and associated diseases, from individuals in the Clydebank region; one sample was excluded for heavy carbon content. Diagnoses included 12 mesotheliomas, five cases of pulmonary fibrosis and one lung cancer.
• Exposure: Known occupational asbestos exposure; fibre types were not identified. The study measured lung fibre burden by two alkali-digestion light-microscope methods (Gold and Kerr; Ashcroft and Heppleston) and graded asbestos bodies in tissue sections.
• Main results:
  • The two methods gave significantly different fibre counts, with lower results for the Gold and Kerr technique (method A) than for the Ashcroft and Heppleston technique (method B).
  • Repeatability was poor. For observer 1, a repeated method A count would be expected to lie between 786% above and 96% below the original count. For observer 2, the range for method A was 4307% above to 96% below.
  • The authors stated that the wide limits of agreement meant a repeated count might not fall in the same exposure category.
  • Asbestos bodies were found in tissue sections from 14 samples. All three pathologists agreed in 12 samples (63%).
  • Both fibre-counting methods gave counts that were inappropriately low in seven samples compared with the number of asbestos bodies seen, particularly when few asbestos bodies were identified.
  • The 12 mesothelioma cases occurred in all asbestos body categories (none, few and many).
  • Asbestos bodies were found in four of the five pulmonary fibrosis cases.
• The authors' conclusion: The authors concluded that counting asbestos bodies by light microscopy is a valuable screening technique. They wrote that finding asbestos bodies, together with a good occupational history, should be accepted as a marker of significant exposure. They said that fibre estimations may help when no asbestos bodies are found, and that the two fibre-counting methods are not interchangeable and need an appropriate reference range.
• Limitations the authors state:
  • The study did not control technical problems such as uneven fibre distribution and fibre breakage during preparation.
  • Asbestos body grading is insensitive: small numbers of asbestos bodies were overlooked in four cases by some observers.
  • Fibre counts examine only a small area of lung and use large multiplication factors.

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, Asbestos Exposure.

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