Relevance of asbestos bodies in sputum

Our plain-English summary of Relevance of asbestos bodies in sputum, by H. Teschler, A.B. Thompson, R. Dollenkamp, et al (The European Respiratory Journal, 1996).

The study

• Authors: H. Teschler, A.B. Thompson, R. Dollenkamp, N. Konietzko, U. Costabel
• Journal: The European Respiratory Journal
• Published: 1996;9(4):680-6
• Cited by: 34 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The presence of asbestos bodies (ABs) in sputum specimens of individuals with occupational asbestos exposure has been well-documented. The aim of this study was to determine their clinical relevance in comparison to the concentration of AB in bronchoalveolar lavage (BAL) and lung tissue. Subjects were included following a well-documented exposure of asbestos history (n = 93) or BAL fluid analysis positive for ABs (n = 42). The subjects with a well documented history of AB exposure were divided into three groups: heavy (Group 1, n = 29); moderate (Group 2, n = 31); or occasional exposure (Group 3, n = 33). BAL fluid was available from all subjects, and lung tissue from 21 subjects. To assess the variability, 10 sputum positive subjects collected subsequent sputum on days 2, 7, 14, 30 and 90. ABs were determined by light microscopy after membrane filtration of specimen digests. The mean sputum AB content was highest in Group 1 (2.4 +/- 5.5 AB.mL-1), lower in Group 2 (0.2 +/- 0.3 AB.mL-1) and lowest in Group 3 (0.1 +/- 0.1 AB.mL-1) suggesting a correlation with cumulative exposure. However, many negative sputum samples were noted, when BAL specimens were positive. The AB content of sputum and BAL specimens did not correlate. ABs were found in sputum of all subjects with a tissue content of > 1,000 AB-cm-3, but in none with contents of < 1,000 AB-cm-3. Substantial variability of ABs was found in the five sequentially collected sputa of 10 initially positive patients (coefficient of variation 28-93%), but only two false negatives were found in these 50 samples. Thus, sputum analysis for asbestos bodies is an insensitive method for assessing the lung asbestos burden, much less sensitive than bronchoalveolar lavage fluid analysis. However, a sputum sample positive for asbestos bodies is suggestive of a high lung asbestos burden.

In plain English

This study compared asbestos body counts in sputum with counts in bronchoalveolar lavage (BAL, fluid washed from the lungs) and, for 21 people, in lung tissue. It included 135 patients with occupational exposure to mixed asbestos dust. The 93 with work histories were grouped as heavy, moderate or occasional exposure. Mean sputum counts were 2.4, 0.2 and 0.1 bodies per mL in these groups. In the three groups, 33%, 68% and 45% of patients had bodies in BAL but none in sputum. Sputum and BAL counts did not correlate. All patients with more than 1,000 bodies per cubic centimetre of wet lung tissue had bodies in sputum, and none below that level did. In 10 sputum-positive patients sampled repeatedly over 90 days, 2 of 50 later samples were negative, but counts varied widely. The authors concluded that sputum analysis is insensitive, much less sensitive than BAL, but that a positive sample suggests a high lung asbestos burden. Some numbers in the article conflict with each other.

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: Clinical comparison study of asbestos body counts by light microscopy in sputum, BAL fluid and lung tissue, with repeated sputum sampling in a subgroup
• Who was studied: 135 patients (115 males, 20 females; mean age 61) with occupational exposure to mixed asbestos dust, who had BAL for suspected asbestos-related disease and could produce sputum. The authors are at the Ruhrlandklinik, Essen, Germany; study dates are not given. Of these, 93 with medical and occupational histories were put into three exposure groups. Lung tissue was available from 21 subjects, and 10 subjects (all smokers with chronic bronchitis) gave repeated sputum samples.
• Exposure: Occupational exposure to mixed asbestos dust. Group 1 (high exposure, over 6 months, 8 hours a day) were asbestos textile workers, insulators or welders. Group 2 (moderate exposure, over 6 months, under 4 hours a day) were welders, mechanical repairers, sheet-metal workers, electricians or foundry workers. Group 3 had occasional exposure.
• Main results:
  • Mean sputum asbestos body content was 2.4 plus or minus 5.5 per mL in Group 1 (heavy exposure), 0.2 plus or minus 0.3 per mL in Group 2 (moderate) and 0.1 plus or minus 0.1 per mL in Group 3 (occasional).
  • Asbestos bodies were found in BAL but not in sputum in 33% of Group 1, 68% of Group 2 and 45% of Group 3.
  • No subject without asbestos bodies in BAL fluid had asbestos bodies in sputum.
  • Across the study population, sputum and BAL asbestos body counts showed no significant correlation (r=0.13, p=0.34).
  • Sputum recovered systematically fewer asbestos bodies than BAL (mean difference -8.2 plus or minus 4.9 per mL; 95% confidence limits -3.3 to -13.1 per mL).
  • In subjects with lung tissue, those with less than 1,000 asbestos bodies per cubic centimetre of wet lung tissue had none in sputum, and all those with more than 1,000 had asbestos bodies in sputum.
  • Among the 11 subjects with asbestos bodies in sputum, sputum counts did not correlate with lung biopsy counts (r=0.26, p=0.34).
  • In the 10 initially sputum-positive subjects, 2 of the 50 later sputum samples contained no asbestos bodies.
  • In the same 10 subjects, the coefficient of variation of repeated sputum counts ranged from 28% to 92% (the abstract and Table 4 give up to 93%).
  • Within each exposure group, sputum asbestos body counts were significantly higher in smokers.
• The authors' conclusion: The authors concluded that sputum analysis for asbestos bodies is an insensitive method for assessing lung asbestos burden, much less sensitive than BAL fluid analysis, but that a sputum sample positive for asbestos bodies is suggestive of a high lung asbestos burden.
• Limitations the authors state:
  • The study had no group of occupationally unexposed people, so it could not address how specific sputum asbestos bodies are as a marker of occupational exposure.
  • Subjects in the repeat-sampling part were chosen for their ability to produce sputum daily, which could bias that analysis.
  • Whether a sample was sputum or spit was judged by its appearance, not by microscopic examination of cells.
  • The study used spontaneous early-morning sputum rather than induced sputum.
  • Reliable exposure data were not available for Group 3.

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, Sputum, Asbestos Exposure, Bronchoalveolar Lavage (BAL), BAL Fluid, Cumulative Exposure.

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• Asbestos bodies in the sputum of asbestos workers: correlation with occupational exposure — C. Paris, F. Galateau-Salle, et al. (2002)
• A method for extracting ferruginous bodies from sputum and pulmonary tissue — M.J. Smith, B. Naylor (1972)
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