Asbestos-related pleural disease and asbestosis: a comparison of CT and chest radiography

Our plain-English summary of Asbestos-related pleural disease and asbestosis: a comparison of CT and chest radiography, by A.C. Friedman, S.B. Fiel, M.S. Fisher, et al (AJR. American Journal of Roentgenology, 1988).

The study

• Authors: A.C. Friedman, S.B. Fiel, M.S. Fisher, P.D. Radecki, A.S. Lev-Toaff, D.F. Caroline
• Journal: AJR. American Journal of Roentgenology
• Published: 1988;150(2):269-75
• Cited by: 130 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. 000219).

Abstract

High-resolution CT (HRCT) has the ability to demonstrate both asbestos-related pleural disease and parenchymal abnormalities consistent with asbestosis. The role of CT in the diagnosis of asbestosis can be defined by comparing it with radiography. We evaluated 60 men who had a history of occupational exposure to asbestos and whose outside chest radiographs were considered abnormal. Chest radiographs (inside films) and HRCT were performed in all patients at our institution and were interpreted independently by experienced radiologists. Outside film results were compiled from the submitted reports. The final conclusion regarding the interpretation of the radiologic examinations was determined by consensus when disagreements existed. Positive predictive values (the likelihood that a positive report is correct) for pleural disease were: outside films 56%, inside films 79%, HRCT 100%. The positive predictive values for parenchymal disease were: outside films 51%, inside films 83%, HRCT 100%. The addition of HRCT to chest radiography is most useful in eliminating false-positive diagnoses of asbestos-related pleural disease caused by subpleural fat and false-positive diagnoses of parenchymal asbestosis in patients with extensive plaques or emphysema obscuring lung detail. The interpretation of chest radiographs in patients exposed to asbestos is often extremely difficult and subjective, and we recommend that positive findings (except calcified plaques) be confirmed with HRCT.

In plain English

This prospective Philadelphia hospital study compared chest X-rays with high-resolution CT (HRCT) scans in 60 men with occupational asbestos exposure whose outside chest films had been read as abnormal. The hospital's own chest films and HRCT scans were read blind. Disagreements were settled by consensus in all but one case, and no tissue confirmation was available. Final diagnoses were asbestos-related pleural disease alone in 13 men, parenchymal asbestosis alone in 2, and both in 19. Another 24 had neither asbestos-related pleural disease nor interstitial lung disease, and 2 had other lung diseases (sarcoid and coal-worker's pneumoconiosis). A positive outside film reading was correct 56% of the time for pleural disease and 51% for asbestosis. For the hospital's films the figures were 79% and 83%, and for HRCT 100% for both. These differences were statistically significant. Most false-positive pleural readings on outside films came from fat beneath the pleura. The authors concluded that reading these X-rays is often difficult and subjective, and they recommended confirming positive findings other than calcified plaques with HRCT. They noted that selection bias limited some measures.

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: Prospective comparison of chest radiography and high-resolution CT (HRCT) in patients referred with suspected asbestos-related disease. Outside film reports were compared with the hospital's own blindly read films and HRCT, and final diagnoses were reached by consensus.
• Who was studied: 60 men (average age 58) referred to Temple University Hospital, Philadelphia, with suspected occupational lung disease and abnormal outside chest films. Outside films had been read as showing asbestos-related pleural disease in 57 and interstitial fibrosis (asbestosis) in 38. None of the outside readers were B-readers; 75% were pulmonary physicians. Study dates are not given.
• Exposure: History of occupational asbestos exposure lasting at least 1 year. Fiber types, products and specific jobs were not reported.
• Main results:
  • Final diagnosis of asbestos-related pleural disease without parenchymal involvement: 13 patients (22%).
  • Final diagnosis of parenchymal asbestosis without pleural disease: 2 patients (3%).
  • Final diagnosis of both asbestos-related pleural disease and parenchymal asbestosis: 19 patients (32%).
  • No evidence of asbestos-related pleural disease or interstitial lung disease: 24 patients (40%). Two further patients (3%) had other interstitial lung diseases (sarcoid and coal-worker's pneumoconiosis).
  • Consensus could not be reached in one case, in which outside and inside films were positive for parenchymal asbestosis and HRCT was negative.
  • Of the 21 patients with parenchymal asbestosis, 6 had restrictive pulmonary function, 5 had obstructive changes only, and 10 had normal pulmonary function tests.
  • Positive predictive values (likelihood that a positive report was correct) for pleural disease: outside films 56%, inside (hospital) films 79%, HRCT 100%.
  • Positive predictive values for parenchymal disease: outside films 51%, inside films 83%, HRCT 100%.
  • The differences in positive predictive values were statistically significant for both pleural and parenchymal disease: p less than 0.05 for outside versus inside films, p less than 0.01 for outside films versus HRCT, and p less than 0.025 for inside films versus HRCT.
  • All 17 false-positive outside film diagnoses of pleural disease where both inside films and HRCT were true-negative were caused by subpleural fat. Of the 8 false positives on both outside and inside films, 7 were caused by subpleural fat and 1 by intercostal muscle.
  • There were no false-positive HRCT findings for either pleural or parenchymal disease.
  • Two inside films were false-negative for pleural disease because of subtle diaphragmatic plaques. One HRCT scan was false-negative because a solitary calcified plaque fell between the slices.
  • In only two cases did HRCT show parenchymal asbestosis not suspected on either outside or inside films.
  • HRCT made additional diagnoses not made on either type of film: emphysema in 7 patients, bronchiectasis in 2, and benign effusion in 1 patient thought to have mesothelioma on the basis of outside films.
• The authors' conclusion: The authors concluded that interpreting chest radiographs of asbestos-exposed patients is often extremely difficult and subjective. Because the positive predictive value of the hospital's films was about 80%, they recommended that radiographic abnormalities other than calcified plaques be confirmed with HRCT. They described HRCT as especially useful for eliminating false-positive plaque diagnoses caused by subpleural fat and false-positive asbestosis diagnoses in patients with emphysema or extensive plaques.
• Limitations the authors state:
  • No pathologic confirmation of diagnosis was obtained. Final diagnoses were clinical.
  • Because of selection bias (all patients entered with positive outside films), the true frequency of false-negative outside film readings could not be established, and outside film sensitivity may be artificially high.
  • Outside film specificity for pleural disease was artificially low because only a few final diagnoses were negative.
  • A study of exposed patients with negative outside films would be needed to best assess negative predictive value, sensitivity and the screening value of HRCT.
  • The greater diagnostic confidence the authors reported with HRCT was difficult to quantify.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Asbestos-Related Pleural Disease, High-Resolution CT (HRCT), Occupational Exposure, Chest X-Ray, Emphysema.

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