The clinical diagnosis of asbestosis in this century requires more than a chest radiograph

Our plain-English summary of The clinical diagnosis of asbestosis in this century requires more than a chest radiograph, by R.M. Ross (Chest, 2003).

The study

• Author: R.M. Ross
• Journal: Chest
• Published: 2003;124(3):1120-8
• Type of article: Review
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestosis can cause significant impairment and even death. It is also a well-recognized risk factor for the development of lung cancer. However, asbestosis is usually diagnosed on clinical grounds without the aid of pathology. Many physicians and researchers believe that in asbestos-exposed individuals with adequate latency, chest radiographic findings that are compatible with asbestosis are sufficient for the diagnosis. In order to determine whether this approach is reasonable, the positive predictive value of the chest radiograph for the diagnosis of pathologic asbestosis must be determined. This requires information about the prevalence of asbestosis, and the sensitivity and specificity of the chest radiograph in its diagnosis. In this article, the sensitivity and specificity of the chest radiograph in diagnosing asbestosis is determined from a literature analysis. The prevalence of asbestosis among present-day cohorts, such as construction workers and petrochemical workers, is assessed based on the relative risk of lung cancer in patients with asbestosis and the overall relative risk of lung cancer in these occupationally asbestos-exposed cohorts. The results indicate a positive predictive value for abnormal chest radiograph findings alone to be significantly < 50%. Therefore, the chest radiograph is inadequate as the sole clinical tool to be used to diagnose asbestosis in these cohorts. However, when rales and a low diffusing capacity of the lung for carbon monoxide are also present, the diagnosis of asbestosis on clinical grounds can be made with reasonable confidence.

In plain English

This article, published in the journal's Opinions/Hypotheses section, reported no new patient data. Its author used a literature analysis and calculations to estimate how often a mildly abnormal chest X-ray (ILO grade 1/0 or 1/1) reflects true asbestosis in present-day North American construction and petrochemical workers exposed to asbestos. From published mortality studies, the author put these workers' extra lung cancer risk at about 16% and estimated that about 1 to 5% of them would have asbestosis. Taking the X-ray's sensitivity as 90% and specificity as 93%, the author calculated how often a positive X-ray alone would be correct (its positive predictive value): about 40% at 5% prevalence and 28% at 3%. Requiring three findings together raised the estimates to about 70% and 60%: an X-ray finding, crackles in the lungs (rales), and a low lung diffusing capacity (DLCO) test. The author concluded that, in the appropriate clinical setting, only this combination allows a clinical diagnosis of asbestosis with reasonable confidence. The author noted that asbestosis prevalence has not been accurately determined.

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: Opinion/hypothesis article based on a literature analysis and calculations (no new data collected)
• Who was studied: Present-day North American asbestos-exposed cohorts, mainly construction and petrochemical (refinery) workers, drawn from large cohort mortality studies published since 1990 (17 studies in Table 1)
• Exposure: Occupational asbestos exposure among workers who used asbestos-containing products rather than those in mining or manufacturing (no fiber type specified). The test examined was a mildly abnormal chest radiograph, ILO grade 1/0 or 1/1.
• Main results:
  • Across the reviewed construction and petrochemical cohort studies, lung cancer risk was increased by about 0 to 40%, averaging about 16% over unexposed control subjects
  • Across all studies in Table 1: 26,285 lung cancer deaths against 22,569 expected; mortality ratio 116
  • The author estimated the prevalence of asbestosis in these cohorts at about 1 to 5%
  • The author estimated the chest radiograph's sensitivity for asbestosis at about 90% and its specificity at 90 to 95%
  • Calculated positive predictive value of a positive chest radiograph alone (ILO 1/0 and 1/1): about 40% at 5% prevalence, using sensitivity 90% and specificity 93%
  • Calculated positive predictive value of the chest radiograph alone at 3% prevalence: 28%
  • Even assuming 95% sensitivity and specificity, the positive predictive value of a high-resolution CT scan alone would be about 50% at 5% prevalence
  • With an assumed combined sensitivity of 70% and specificity of 98.5%, the positive predictive value when chest radiograph, rales and DLCO are all abnormal was about 70% at 5% prevalence
  • For the same three-test combination at 3% prevalence, the positive predictive value was about 60%
• The authors' conclusion: The author concluded that the chest radiograph should not be the sole diagnostic tool in these cohorts. In the author's view, a clinical diagnosis of asbestosis can be made with reasonable confidence only in the appropriate clinical setting, and only when compatible chest radiograph findings, rales and a reduced DLCO are all present.
• Limitations the authors state:
  • The prevalence of pathologic asbestosis in asbestos-exposed workers has not been accurately determined
  • The increased lung cancer risk in the reviewed cohorts may not be due solely to asbestos; most studies did not control for smoking or other workplace carcinogens
  • How far the three tests depend on one another has not been carefully examined
  • The actual specificity of DLCO for diagnosing asbestosis is not known with certainty

Topics

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

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Lung Cancer, Pathology, Latency, Relative Risk, Diffusing Capacity (DLCO).

Related studies

• Antemortem diagnosis of asbestosis by screening chest radiograph correlated with postmortem histologic features of asbestosis: a study of 273 cases — K.N. Mizell, C.G. Morris, et al. (2009)
• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)
• Incremental value of oblique chest radiographs in the diagnosis of asbestos-induced pleural disease — E.L. Baker, R. Greene (1982)
• Asbestos-related radiographic changes by ILO classification of 10 x 10 cm chest X-rays in a screening of the general population — B. Hilt, G. Hillerdal, et al. (1995)
• Accurate diagnosis of mesothelioma: more important than ever — T.C. Allen (2013)
• Chest radiographs in subjects with asbestos-related abnormalities: comparison between ILO categorizations and clinical reading — B. Hilt, A. Borgerson, et al. (1992)

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