Computed tomography in the early detection of asbestosis

Our plain-English summary of Computed tomography in the early detection of asbestosis, by R. Bégin, G. Ostiguy, R. Filion, et al (British Journal of Industrial Medicine, 1993).

The study

• Authors: R. Bégin, G. Ostiguy, R. Filion, N. Colman, P. Bertrand
• Journal: British Journal of Industrial Medicine
• Published: 1993;50(8):689-98
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Computed tomography (CT; both conventional (CCT) and high resolution (HRCT)) scans of the thorax were evaluated to detect early asbestosis in 61 subjects exposed to asbestos dust in Québec for an average of 22(3) years and in five controls. The study was limited to consecutive cases with chest radiographs of the International Labour Organisation categories 0 or 1 determined independently. All subjects had a standard high kilovoltage posteroanterior and lateral chest radiograph, a set of 10-15 1 cm collimation CCT scans and a set of three to five 2 mm collimation HRCT scans in the upper, middle, and lower lung fields. Five experienced readers independently read each chest radiograph and sets of CT scans. On the basis of three to five readers agreeing for small opacities of the lung parenchyma, 12/46 (26%) negative chest radiographs were positive on CT scans, but 6/18 (33%) positive chest radiographs were negative on CT scan. On the basis of four to five readers agreeing on a chest radiograph, 36/66 (54%) subjects were normal (group A), 17/66 (26%) were indeterminate (group B), and 13/66 (20%) were abnormal (group C). By the combined readings of CCT and HRCT, 4/31 (13%) asbestos exposed subjects of group A were abnormal (p < 0.001), 6/17 (35%) of group B were abnormal, and in group C, 1/13 (8%) was normal, 2/13 were indeterminate, and 10/13 (77%) were abnormal. Separate readings of CCT and HRCT on distinct films in 14 subjects showed that all cases of asbestosis were abnormal on both CCT and HRCT. Inter-reader analyses by kappa statistics showed significantly better agreement for the readings of CT than the chest radiographs (p < 0.001), and for the reading of CCT than HRCT (p < 0.01). Thus CT scans of the thorax identifies significantly more irregular opacities consistent with the diagnosis of asbestosis than the chest radiograph (20 cases on CT scans v 13 on chest radiographs when four to five readers agreed, 13% of asbestos exposed subjects with normal chest radiographs or 21% of asbestos exposed subjects with normal or near normal chest radiographs. It decreased the number of indeterminate cases significantly from 17 on chest radiographs to 13 on CT scans. All cases of asbestosis detected only on CT scans were similarly seen on CCT and HRCT and did not have significant changes in lung function. The CT scans significantly reduced the inter-reader variability, despite the absence of ILO type reference films for these scans.

In plain English

This study compared chest X-rays with conventional and high resolution computed tomography (CT) scans for detecting early asbestosis. The subjects were 61 consecutive patients referred by the Workman's Compensation Board of Quebec after exposure to asbestos dust in the Quebec asbestos industries for an average of 22 years, plus five unexposed controls. Five experienced readers independently graded each X-ray and CT scan. When four or five readers had to agree, CT scans suggested asbestosis in 4 of 31 exposed workers with normal X-rays (13%) and in 6 of 17 with uncertain X-rays. Of 13 workers with abnormal X-rays, 10 had abnormal CT scans. Readers agreed with each other more on CT scans than on X-rays. Workers with a normal X-ray but an abnormal CT scan did not show significant changes in lung function. The authors concluded that CT was more sensitive than the X-ray in detecting lung changes of asbestosis. They noted that they had no histological (tissue) proof that the CT findings were asbestosis.

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: Imaging comparison study: chest radiographs and CT scans of the same subjects were read independently by five readers and compared with each other and with lung function tests
• Who was studied: 61 consecutive patients referred by the Workman's Compensation Board of Quebec for evaluation of possible asbestos-related lung disease, all with chest radiographs in ILO category 0 or 1, plus 5 healthy non-smoking, non-exposed, age-matched controls (66 subjects in total, mean age 62)
• Exposure: Asbestos dust in the Quebec asbestos industries (fiber type not specified), for an average of 22 years (range 1 to 42 years), measured as years of employment in a work environment containing asbestos dust
• Main results:
  • When three to five readers had to agree, 12 of 46 subjects (26%) with negative chest radiographs had CT scans positive for asbestosis. When four to five readers had to agree, the figure was 4 of 36 (11%).
  • Among the 36 subjects with normal chest radiographs (group A, which included the 5 controls), 4 had abnormal CT scans suggestive of asbestosis. That is 11% of the group, or 13% of the 31 asbestos-exposed subjects in it.
  • Among the 17 subjects with indeterminate chest radiographs (group B), 6 (35%) had abnormal CT scans.
  • Among the 13 subjects with abnormal chest radiographs (group C), 1 (8%) had a normal CT scan, 2 (15%) had indeterminate CT scans and 10 (77%) had abnormal CT scans.
  • On CT, all 66 subjects were classified as follows: 33 (50%) normal, 13 (20%) indeterminate and 20 (30%) abnormal.
  • Agreement between readers on positive versus negative readings had a kappa of 0.44 for chest radiographs and 0.63 for CT scans (p less than 0.05).
  • Subjects with both an abnormal radiograph and an abnormal CT scan (n = 10) had significantly altered lung function compared with subjects negative on both (n = 26).
  • Subjects with a negative radiograph but a positive CT scan (n = 10) did not have significant changes in lung function compared with subjects negative on both.
  • In 14 positive cases read separately, conventional CT and high resolution CT were both abnormal in every case of asbestosis.
  • Reader agreement (kappa) in these 14 cases was 0.84 for conventional CT and 0.73 for high resolution CT.
• The authors' conclusion: The authors concluded that CT scans were more sensitive than the standard ILO-classified chest radiograph in detecting lung parenchymal changes of asbestosis
• Limitations the authors state:
  • There was no histological proof that the small opacities seen on CT in workers with normal radiographs were early asbestosis
  • The comparison of conventional and high resolution CT used only 14 subjects and a limited number of thin CT slices, which may not permit definite conclusions
  • The study had a selection bias and limited samples, so the multiple variate analyses were not meant to establish definite associations
  • Additional lung function tests did not reach significance because only 50% of patients agreed to perform them
  • No standard ILO-type reference films existed for grading the CT scans

Topics

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

Medical terms in this study, explained in our Lexicon: High-Resolution CT (HRCT), Thorax, Chest X-Ray, CT Scan, Parenchyma.

Related studies

• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)
• Early detection of interstitial lung disease in asbestos exposed non-smoking workers by mid-expiratory flow rate and high resolution computed tomography — Z. Dujić, J. Tocilj, et al. (1991)
• Diagnosis of asbestosis by a time expanded wave form analysis, auscultation and high resolution computed tomography: a comparative study — N. al Jarad, B. Strickland, et al. (1993)
• Is it useful to combine sputum cytology and low-dose spiral computed tomography for early detection of lung cancer in formerly asbestos-exposed power industry workers? — M.K. Felten, L. Knoll, et al. (2014)
• High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs — C.A. Staples, G. Gamsu, et al. (1989)
• 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)

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