Microfiltration method for quantitative study of fibrous particles in biological specimens

Our plain-English summary of Microfiltration method for quantitative study of fibrous particles in biological specimens, by J. Bignon, P. Sebastien, M.C. Jaurand, et al (Environmental Health Perspectives, 1974).

The study

• Authors: J. Bignon, P. Sebastien, M.C. Jaurand, B. Hem
• Journal: Environmental Health Perspectives
• Published: 1974;9:155-60
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Counting coated and uncoated inorganic fibers in sputum has been used to investigate the level of environmental or occupational asbestos exposure and the concentration of fibrous dusts in human lung. Inorganic fibers in sputum were counted by light microscopy after chemical digestion and microfiltration processing. The same method was used for processing gastric juice and lung tissue. There were no ferruginous bodies (FB) in sputum from 49 patients without any asbestos exposure. The study of sputum from 125 patients with various asbestos exposure pointed out a high correlation between the number of FB in sputum and the level of asbestos exposure. These 125 patients were classified into three groups according to the type of their asbestos occupational hazard: group I, raw asbestos workers; group II, workers manufacturing asbestos products; group III, workers with mixed industrial dust exposure. For these three groups, the mean number of FB in sputum was 100, 10, and 1, respectively. The comparison of the FB content of sputum and lung parenchyma showed the absence of FB in sputum when the concentration of FB in lung parenchyma was under 1000/cm(3) of lung parenchyma; above this concentration the number of FB in sputum was in good correlation with fiber concentration in lung parenchyma. A preliminary study with the use of gastric juice showed that gastric juice is a less sensitive sample for evaluating fiber concentration in lung. The microfiltration method for the counting of uncoated fibers gave results as accurate as those in the centrifugation method.

In plain English

This paper described a laboratory method for counting asbestos-related particles in body samples. Samples were chemically digested, passed through a filter, and examined under a light microscope for ferruginous (coated) bodies and uncoated fibers. The authors used it on 200 sputum samples from 125 patients (122 men, 3 women) suspected of asbestos exposure. The patients were grouped as raw asbestos workers, workers making or using asbestos products, and workers exposed to mixed industrial dust. Ferruginous bodies were found in 85% of raw asbestos workers and in at least 25% of the mixed-dust group. The article's summary gives group means of 100, 10 and 1 ferruginous bodies per sputum sample. Among 31 patients who each gave three sputum samples, positive results in the mixed-dust group rose from 5% after one sample to almost 50% after three. In lung tissue comparisons, sputum was always negative when the lung held under 1000 ferruginous bodies per cubic centimeter. Gastric juice results were preliminary. The authors concluded that sputum counts could serve as a laboratory screening test. They noted that the method was time-consuming and needed two or three samples.

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 methods study (chemical digestion, microfiltration and light-microscope counting) applied to a clinical series of patients, with comparisons against lung tissue, preliminary gastric juice results, and a check against the centrifugation method
• Who was studied: 200 sputum samples from 125 patients (122 men, 3 women; mean age 54 years), all suspected of asbestos exposure. Group I had 16 patients, group II 42 and group III 64. Three sputum samples were examined in a subset of 31 cases. Lung parenchyma was compared with sputum in 38 cases, and gastric juice results are listed for 7 cases. The article does not state where or when patients were recruited; the authors were based in Paris.
• Exposure: Occupational asbestos exposure in three groups. Group I: raw asbestos workers (milling, spinning and projecting raw asbestos). Group II: workers who manufactured or used asbestos-containing products such as insulation or brake linings. Group III: workers exposed to mixed industrial dust including asbestos. Fiber types were not named.
• Main results:
  • The authors reported a significant association between ferruginous bodies in sputum and degree of exposure. The most heavily exposed group (group I, raw asbestos workers) had the highest percentage of positive cases, 85%.
  • In group III (mixed industrial dust), at least 25 percent of cases had ferruginous bodies in their sputum.
  • The article's summary gives mean numbers of ferruginous bodies in sputum of 100 (group I), 10 (group II) and 1 (group III). The article expresses sputum counts as the total number per sputum.
  • Three sputum samples were examined in a subset of 31 cases. Within that subset, group I was positive in all cases from the first sample. Group III was positive in 5% of cases at the first examination and in almost 50% after three samples.
  • The number of ferruginous bodies in sputum was more than 10 in almost all patients with severe occupational exposure.
  • By disease, ferruginous bodies were found in the sputum of 7 of 9 mesothelioma cases (site not stated), 21 of 23 lung fibrosis cases and 16 of 23 lung carcinoma cases.
  • When lung tissue was compared with sputum, sputum was always negative in the 31 cases with fewer than 1000 ferruginous bodies per cubic centimeter of lung. In 9 cases above that level, sputum counts correlated well with lung concentration. The authors called these data preliminary.
  • Uncoated fibers were counted in 14 cases (8 sputum, 6 lung tissue). In these cases, uncoated fibers made up between 15 and 85% of all fibers.
  • In the check against centrifugation, no fibers remained inside the filter. In one case, about 0.05% of uncoated fibers were lost through the filter. The authors judged microfiltration as accurate as centrifugation for the proportion of coated and uncoated fibers.
  • In preliminary gastric juice results, the correlation between ferruginous bodies in sputum and in gastric juice was low so far. The authors suggested this may be explained by the time between the patient waking and the sample being taken.
• The authors' conclusion: The authors concluded that microfiltration of sputum appears to be a reliable way to quantify ferruginous bodies and uncoated fibers in the lung. They said counting ferruginous bodies in sputum, and perhaps in gastric juice, could be used as a laboratory screening test, particularly when exposure is unknown, and to monitor exposed workers.
• Limitations the authors state:
  • Two or three sputum samples need to be studied, and the method is time-consuming.
  • The gastric juice study was still in progress, and only preliminary results were given.
  • The correlation between sputum and lung tissue rested on preliminary data.
  • Uncoated fibers were counted in only 14 cases.

Topics

Medical terms in this study, explained in our Lexicon: Sputum, Asbestos Exposure, Ferruginous Bodies, Parenchyma.

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