Assessment of hazardous dust exposure by BAL and induced sputum

Our plain-English summary of Assessment of hazardous dust exposure by BAL and induced sputum, by E. Fireman, J. Greif, Y. Schwarz, et al (Chest, 1999).

The study

• Authors: E. Fireman, J. Greif, Y. Schwarz, A. Man, E. Ganor, Y. Ribak, Y. Lerman
• Journal: Chest
• Published: 1999;115(6):1720-8
• Cited by: 52 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: BAL, an important tool in assessing occupational lung diseases, is unsuitable for screening programs, exposure evaluation, or monitoring hazardous dust because it is an invasive technique. The results of induced sputum (IS) analysis were compared with BAL and evaluated as a possible alternative.

Methods: We compared BAL with IS analysis of 5 workers exposed to asbestos and 14 exposed to silica and hard metals. Pulmonary function tests and BAL were performed by conventional methods. IS induction was performed after a 20-min inhalation of 3.5% saline solution with an ultrasonic nebulizer. Giemsa-stained cytopreparations were differentially counted. T-lymphocyte subsets were analyzed by flow-activated cell sorter, and messenger RNA (mRNA) was transcribed by reverse transcriptase-polymerase chain reaction. Mineralogic particles were analyzed by scanning electron microscopy and polarizing light microscopy and quantified by an analyzer.

Results: The percentage of neutrophils was significantly lower in BAL fluid than in IS specimens, whereas no differences were found in the percentage of lymphocytes and subsets profile. Asbestos fibers were found in BAL but not in IS samples from workers exposed to asbestos. Polarizing particles were found in both samples. Similar mineral elements were found in qualitative analysis by scanning electron microscopy. Quantitative studies showed similar size distribution with a small shift toward larger particles in sputum; mRNA showed the same cytokine profile.

Conclusions: A comparison of BAL and IS specimens in the evaluation of the study population yielded similar quantitative and qualitative results. Further research is needed to evaluate the hypothesis that IS, being a noninvasive technique, may be useful in monitoring exposed workers.

In plain English

This Israeli study compared two ways of sampling lung material in 19 dust-exposed workers referred for suspected pneumoconiosis. One was bronchoalveolar lavage (BAL), done through a bronchoscope. The other was induced sputum, coughed up after inhaling salt-water mist. Five had worked with asbestos and 14 with silica or silica and hard metals. In both groups, BAL samples had a significantly higher share of macrophages and a lower share of neutrophils than sputum; lymphocyte levels did not differ significantly. In three of the five asbestos workers, fibers were found in BAL samples but not in sputum. In the silica and hard-metal workers, mineral elements identified by electron microscopy were identical or very similar between the methods. Particle size patterns in three patients were similar, and cytokine mRNA profiles in four workers were broadly similar, with one IL-6 difference. No patient had side effects from sputum induction. The authors concluded that the two methods gave similar results in this group. They said more research is needed to test whether induced sputum, being noninvasive, may be useful for monitoring exposed workers. They studied no unexposed comparison group.

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 of two lung-sampling methods, bronchoalveolar lavage (BAL) and induced sputum, performed in the same workers.
• Who was studied: 19 hazardous-dust workers with suspected pneumoconiosis, followed under Israeli occupational regulations and evaluated at a Tel-Aviv clinic. Group 1 was 5 asbestos-exposed workers; group 2 was 14 workers exposed to silica or to silica and hard metals.
• Exposure: Group 1: asbestos at an electric power plant (thermal insulation), at an asbestos cement factory using chrysotile and crocidolite (ratio printed as 1:10, crocidolite later eliminated), and in cutting and sawing asbestos sheets as a military fitter. Group 2: silica dust or silica plus hard metals (clay production, tile laying, marble processing, hard-metal grinding, foundry work).
• Main results:
  • In both groups, the percentage of macrophages was significantly higher and the percentage of neutrophils significantly lower in BAL than in induced sputum. Group 1 (asbestos), Table 2: macrophages 85.2% in BAL vs 37.0% in sputum; neutrophils 2.2% vs 50.2%. Group 2: macrophages 85.7% vs 39.8%; neutrophils 3.5% vs 52.2%. Table footnotes give p = 0.0022 for macrophages and p = 0.0077 for neutrophils.
  • Group 1 (asbestos workers): lymphocytes were 11.8 ± 7.6% in BAL vs 11.3 ± 2.8% in sputum (p = 0.893). The CD4/CD8 ratio was 3.9 ± 1.7 vs 4.0 ± 1.2 (p = 0.723). These differences were not significant.
  • Group 2 (silica and hard-metal workers): lymphocytes were 9.5 ± 7.8% in BAL vs 6.4 ± 5.5% in sputum (p = 0.638). The CD4/CD8 ratio was 1.4 ± 0.7 vs 1.9 ± 1.0 (p = 0.128). These differences were not significant.
  • In three of the five asbestos-exposed workers, fibers were found in BAL samples but not in sputum samples.
  • The authors reported that polarized light gave identical results with both methods in the silica and hard-metal group. However, Table 3 as printed lists patient 12 as positive in BAL and negative in sputum.
  • In the silica and hard-metal group (group 2), mineral analysis by scanning electron microscopy gave identical results in both samples for some workers (nos. 5, 7, 8 and 10) and very similar results for the others. This statement follows the authors' description of the silica and hard-metal group, and the patient numbers match group 2 in Table 3.
  • In three patients, particles recovered by BAL and by sputum showed the same size distribution pattern, with a small shift toward larger particles in sputum.
  • In those three patients, particles smaller than 2.5 micrometres made up 75.8 ± 17.2% of particles in BAL samples and 68 ± 19.0% in sputum samples (p = 0.10).
  • Cytokine mRNA profiles were tested in BAL and sputum cells from two group 1 and two group 2 workers. The authors reported no differences in the profiles between the two methods.
  • Table 4 shows one exception to identical mRNA profiles: in group 2, IL-6 mRNA was found in 2 of 2 BAL samples but in 1 of 2 sputum samples. In group 1 it was found in 2 of 2 with both methods.
  • None of the patients had side effects from sputum induction.
  • Radiologic changes typical for pneumoconiosis were seen in 3 of 5 asbestos workers and in 12 of 14 silica and hard-metal workers.
  • Diffusing capacity for carbon monoxide was significantly lower in group 2 than in group 1: 72.1 ± 18.0% vs 104.4 ± 8.32% of predicted (p = 0.0014).
• The authors' conclusion: The authors concluded that BAL and induced sputum gave similar quantitative and qualitative results in this study population. They said further research is needed to test whether induced sputum, being noninvasive, may be useful for monitoring exposed workers.
• Limitations the authors state:
  • No normal (unexposed) control subjects were studied.
  • Workplace environmental measurements were available for only 9 of the 19 subjects.
  • The work was done under optimal clinical laboratory conditions. Screening at the workplace would need skilled technicians, because too little expectorated material can give false-negative results.

Topics

Medical terms in this study, explained in our Lexicon: Sputum, Occupational Lung Disease, Pulmonary Function Test (PFT), Scanning Electron Microscopy (SEM), BAL Fluid, Cytokine.

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