Reproducibility of asbestos body counts in digestions of autopsy and surgical lung tissue

Our plain-English summary of Reproducibility of asbestos body counts in digestions of autopsy and surgical lung tissue, by M.I. Velasco-García, M.J. Cruz, L. Ruano, et al (American Journal of Industrial Medicine, 2011).

The study

• Authors: M.I. Velasco-García, M.J. Cruz, L. Ruano, M.A. Montero, A. Freixa, J. Ferrer
• Journal: American Journal of Industrial Medicine
• Published: 2011;54(8):597-602
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Asbestos body (AB) counting by a single observer is the most commonly used objective technique to demonstrate asbestos deposition in the lung. In this study, the accuracy and reliability of this procedure is analyzed by evaluating the degree of agreement between two experienced readers.

Methods: Lung tissue specimens from 66 individuals, most of whom had not been exposed to asbestos, were studied: 35 were obtained in postmortem studies (upper, middle, and lower lung) and 31 were from patients who underwent surgery for lung cancer. Overall, 167 samples were analyzed. Lung tissue sections weighing 0.5 g were obtained prospectively and processed, and the inorganic residue was analyzed by light microscopy at 400× magnification by two experienced readers. Results were expressed as AB/g of dry lung tissue. Interobserver variability was analyzed using the Spearman correlation coefficient and agreement was evaluated by the Bland-Altman method and the kappa index.

Results: The interobserver correlation was 0.8975: 0.8029 for autopsy samples and 0.9592 for biopsy samples. Bland-Altman plots showed that most values were grouped around the 95% limits of agreement. The kappa index was 0.87 for all samples, and 0.79, 0.65, and 0.54 for upper, middle, and lower lung specimens, respectively.

Conclusions: Asbestos body counting by a single reader is a reliable method, especially at low concentrations of asbestos bodies in lung tissue. Double reading may be indicated in borderline cases with asbestos body levels close to levels of 1 000 AB/g.

Copyright © 2011 Wiley-Liss, Inc.

In plain English

This study, from Barcelona, Spain, tested how closely two experienced readers agreed when counting asbestos bodies under a light microscope in digested lung tissue. Tissue came from 35 people examined after death who had no medical record of respiratory disease, and from 31 patients who had surgery for lung cancer. The authors state that most had not been occupationally exposed to asbestos. Both readers counted every sample: 105 autopsy samples from three lung zones and 64 surgical samples. Overall agreement was high (correlation 0.8975; kappa 0.869). It was higher for surgical samples (kappa 0.930) than for autopsy samples (kappa 0.645), and lowest for the base of the lower lobe (kappa 0.535). Reader 1's counts averaged 20% higher than reader 2's. Both readers found more than 1,000 asbestos bodies per gram of dry tissue, the level treated as significant, in five specimens. Only reader 1 did so in one more. The authors concluded that single-reader counting is reliable, especially at low counts, and that double reading may be indicated near 1,000 per gram. They cautioned that the results may not apply to more highly exposed people.

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: Interobserver reproducibility study: two experienced readers each counted asbestos bodies by light microscopy in the same lung tissue digests from autopsy and surgical specimens.
• Who was studied: 66 individuals in Barcelona, Spain. Group A was 35 cadavers of persons with no medical record of respiratory disease, examined at the Forensic Anatomy Institute of Barcelona, giving 105 samples from three zones of the right lung. Group B was 31 lung cancer patients who had surgery at Hospital Vall d'Hebron, giving 64 samples. Study dates are not given.
• Exposure: Lung asbestos body content per gram of dry lung tissue, counted by light microscopy. Asbestos exposure was assessed by questionnaire. The authors state most participants had not been occupationally exposed. Fiber types were not identified.
• Main results:
  • Spearman correlation between the two readers was 0.8975 for all samples, 0.8029 for the autopsy samples (group A) and 0.9592 for the surgical (biopsy) samples (group B).
  • Using three count categories (0 to 300, 301 to 1,000, and more than 1,000 asbestos bodies per gram), the kappa index was 0.869 for all samples (Table I 95% CI 0.766 to 0.972).
  • Kappa was 0.645 for group A (autopsy) and 0.930 for group B (surgical).
  • Within group A, kappa was 0.785 for zone 1 (apex of the upper lobe), 0.653 for zone 2 (apex of the lower lobe) and 0.535 for zone 3 (base of the lower lobe). The abstract rounds these as 0.79, 0.65 and 0.54 for 'upper, middle, and lower' lung.
  • On average, reader 1 reported 20% more asbestos bodies per gram than reader 2.
  • Median counts were 21 (reader 1) and 19 (reader 2) asbestos bodies per gram in group A, and 102 (reader 1) and 72 (reader 2) in group B.
  • Six individuals had counts above 1,000 asbestos bodies per gram: one from group A and five from group B. Both readers reported more than 1,000 in five specimens. In one other case only reader 1 did. The authors report 83% interobserver agreement for counts above 1,000.
  • In two other surgical samples, the two readers' counts fell on opposite sides of 5,000 asbestos bodies per gram.
• The authors' conclusion: The authors concluded that asbestos body counting showed good reproducibility, especially at low concentrations, and can be done reliably by a single reader. They recommended double reading when the count is close to 1,000 asbestos bodies per gram or higher.
• Limitations the authors state:
  • Most participants had relatively low lung asbestos body content and had not been occupationally exposed. Further studies are needed to know whether the results apply to more highly exposed individuals.
  • Light microscopy has limited ability to detect uncoated fibers, so it underestimates total lung asbestos burden.
  • Chrysotile forms asbestos bodies poorly, which limits light microscopy for measuring chrysotile lung burden.

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, Autopsy, Deposition, Lung Cancer, Biopsy.

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