Physiologic categorization of asbestos-exposed workers

Our plain-English summary of Physiologic categorization of asbestos-exposed workers, by P. Harber, D.P. Tashkin, M. Lew, et al (Chest, 1987).

The study

• Authors: P. Harber, D.P. Tashkin, M. Lew, M. Simmons
• Journal: Chest
• Published: 1987;92(3):494-9
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000319).

Abstract

Categorization of the pattern of physiologic abnormalities in patients with asbestos-associated disease may be important for clinical, compensation, and epidemiologic reasons. A population of 658 asbestos-exposed workers was divided into six groups (restrictive, mixed restrictive-obstructive, obstructive, abnormal diffusing capacity, small airway disease, and normal) based upon pulmonary function test results. Use of two commonly employed prediction equations for diffusing capacity produced divergent results. Adjustment of the forced vital capacity for airtrapping based upon measurement of residual volume or of total lung capacity can improve the accuracy of categorization, particularly in smokers. Hence, the process of interpretation of pulmonary function testing should be chosen carefully.

In plain English

The authors analyzed lung function tests from 658 men evaluated for possible asbestos-associated lung disease at UCLA between 1979 and 1984. They averaged 20.7 years of asbestos exposure. Each man was sorted, under several methods, into one of six patterns: restrictive, mixed restrictive-obstructive, obstructive, abnormal diffusing capacity only, small airway disease, or normal. Among all subjects, without race or residual volume adjustment, the Crapo equation for diffusing capacity placed 164 men in the diffusing-capacity-only group, against 34 with the Cotes equations. Adjusting forced vital capacity for air trapping by residual volume shrank the mixed group from 78 to 47 among all subjects (with race adjustment) and from 29 to 14 among current smokers. The effect was small in nonsmokers. Among all subjects, race adjustment of spirometry cut the restrictive group from 50 to 31 and the mixed group from 102 to 78. Among the 644 men in this comparison, categories based on total lung capacity agreed with residual-volume-adjusted ones in 92 percent of cases. The authors concluded these choices need careful consideration. They noted the study did not test which method is best against external criteria such as tissue examination.

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: Cross-sectional analysis of pulmonary function test results, comparing how different interpretation methods change the categorization of workers
• Who was studied: 658 men evaluated for possible asbestos-associated lung disease by the Occupational Medicine Branch, Pulmonary Division, UCLA, between 1979 and 1984. The article describes them as asbestos compensation claimants. Ages ranged from 25 to 83 (mean 56.0). Forty-three percent were black.
• Exposure: Asbestos exposure; fiber types, products and jobs not specified. Mean duration of exposure was 20.7 years (standard deviation 10.2).
• Main results:
  • All subjects, with neither race adjustment nor residual volume adjustment: the Crapo equation placed 164 subjects in the diffusing-capacity-only category, compared with 34 subjects using the Cotes equations.
  • All subjects, with race adjustment: residual volume adjustment of forced vital capacity reduced the mixed group from 78 to 47, and the obstructive group increased.
  • Current smokers: residual volume adjustment reduced the mixed group from 29 to 14 subjects.
  • Nonsmokers: the effect of residual volume adjustment was small.
  • Using total lung capacity instead of residual volume for the air-trapping adjustment produced similar effects, but more subjects remained in the mixed group.
  • All subjects: race adjustment of spirometry values reduced the restrictive group from 50 to 31 and the mixed group from 102 to 78. Similar effects were noted in current smokers and nonsmokers.
  • Race adjustment by multiplying predicted values by 0.85 led to fewer persons being categorized as abnormal than the AMA method of dividing observed values by 0.9.
  • The correlation between total lung capacity residual and residual volume residual was 0.70 for all subjects, 0.68 for current smokers and 0.75 for nonsmokers (each p less than 0.01).
  • Categorization based on total lung capacity agreed with categorization based on residual-volume-adjusted forced vital capacity in 92 percent of cases.
  • The comparison of total-lung-capacity-based and residual-volume-adjusted categories (Table 5) covered 644 subjects, not all 658.
• The authors' conclusion: The authors concluded three things. Prediction equations for diffusing capacity must be chosen carefully, and use of the Crapo and Morris equations needs very careful consideration despite AMA and American Thoracic Society recommendations. Racial factors can significantly affect categorization based on spirometry. Adjusting forced vital capacity for expiratory air trapping can increase the accuracy of categorization.
• Limitations the authors state:
  • The study did not use external criteria, such as pathologic examination of tissue, to determine which method is best.
  • The difference between the diffusing capacity equations probably underestimates the true situation. This is because persons with abnormal spirometry were categorized without regard to diffusing capacity results.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Diffusing Capacity (DLCO), Pulmonary Function Test (PFT), Total Lung Capacity (TLC).

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• Low exposure to asbestos. Gas exchange in ship pipe coverers and controls — R.L. Murphy, E.A. Gaensler, et al. (1972)
• The validity of static lung compliance in asbestos-induced diseases — J. Schneider, R. Arhelger, et al. (2012)
• Ventilatory decrements in former asbestos cement workers: a four year follow up — C.G. Ohlson, L. Bodin, et al. (1985)
• Relationship between chest X-ray findings and pulmonary function tests in dust workers — Y. Tonori, M. Niitsuya, et al. (2005)

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