Asbestos-related disease: progression of parenchymal abnormalities on high-resolution CT

Our plain-English summary of Asbestos-related disease: progression of parenchymal abnormalities on high-resolution CT, by C.I. Silva, N.L. Müller, J.A. Neder, et al (Journal of Thoracic Imaging, 2008).

The study

• Authors: C.I. Silva, N.L. Müller, J.A. Neder, C.R. Nogueira, L.M. Nápolis, M. Terra-Filho, E. Bagatin, L.E. Nery
• Journal: Journal of Thoracic Imaging
• Published: 2008;23(4):251-7
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To evaluate the changes over time in the pattern and extent of parenchymal abnormalities in asbestos-exposed workers after cessation of exposure and to compare 3 proposed semiquantitative methods with a careful side-by-side comparison of the initial and the follow-up computed tomography (CT) images.

Materials And Methods: The study included 52 male asbestos workers (mean age+/-SD, 62.2 y+/-8.2) who had baseline high-resolution CT after cessation of exposure and follow-up CT 3 to 5 years later. Two independent thoracic radiologists quantified the findings according to the scoring systems proposed by Huuskonen, Gamsu, and Sette and then did a side-by-side comparison of the 2 sets of scans without awareness of the dates of the CT scans.

Results: There was no difference in the prevalence of the 2 most common parenchymal abnormalities (centrilobular small dotlike or branching opacities and interstitial lines) between the initial and follow-up CT scans. Honeycombing (20%) and traction bronchiectasis and bronchiolectasis (50%) were seen more commonly on the follow-up CT than on the initial examination (10% and 33%, respectively) (P=0.01). Increased extent of parenchymal abnormalities was evident on side-by-side comparison in 42 (81%) patients but resulted in an increase in score in at least 1 semiquantitative system in only 16 (31%) patients (all P>0.01, signed test).

Conclusions: The majority of patients with previous asbestos exposure show evidence of progression of disease on CT at 3 to 5 years follow-up but this progression is usually not detected by the 3 proposed semiquantitative scoring schemes.

In plain English

This study followed 52 men previously exposed to asbestos: 19 asbestos-cement workers and 33 chrysotile asbestos miners. They were referred for medico-legal evaluation between January 1998 and October 2005 and had no further asbestos exposure between two high-resolution CT scans taken on average 4.1 years apart (range 3 to 5). Two thoracic radiologists who did not know the scan dates scored the scans with three published systems (Gamsu, Huuskonen and Sette). They also compared each pair of scans side by side. Side-by-side comparison showed progression of lung-tissue (parenchymal) abnormalities in 42 (81%) of the 52 men. Only 16 (31%) had a higher score on at least one scoring system by both radiologists, and 7 (14%) on all three. Across the 104 readings, honeycombing was seen in 10% at baseline and 20% at follow-up, and traction bronchiectasis or bronchiolectasis in 33% and 50%. Emphysema and pleural plaques showed no significant change. The authors concluded that the progression was mild and often did not change the scores of the three systems. They noted limitations including the small number of patients, relatively short follow-up, different scanners and no tissue (histologic) confirmation.

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: Follow-up study of consecutive referred asbestos-exposed workers, each with a baseline and a repeat high-resolution CT scan more than 3 years apart. The scans were read independently by two radiologists using three semiquantitative scoring systems and a side-by-side comparison.
• Who was studied: 52 men (mean age 62.2 years, range 41 to 79): 19 asbestos-cement workers and 33 chrysotile asbestos miners. They were among consecutive previously asbestos-exposed workers referred for evaluation for medico-legal reasons from January 1998 to October 2005. Twelve (23%) had never smoked.
• Exposure: Occupational asbestos exposure as asbestos-cement workers or chrysotile asbestos miners. Mean duration of exposure was 13.17 years (range 0.4 to 32). The mean time from first exposure to the initial CT was 33 years (range 17 to 52).
• Main results:
  • On side-by-side comparison of baseline and follow-up scans, parenchymal abnormalities progressed in 42 (81%) of the 52 patients.
  • Only 16 (31%) of the 52 patients had a higher score on at least one of the three scoring systems at follow-up by both observers, and only 7 (14%) had a higher score on all three.
  • Among patients whose Gamsu score stayed the same, side-by-side comparison still showed progression in 27/37 (73%) for observer 1 and 29/39 (74%) for observer 2. Similar proportions were reported for the Huuskonen and Sette systems.
  • In the summed readings of both radiologists (104 readings), honeycombing was seen in 20% at follow-up versus 10% at baseline. Traction bronchiectasis/bronchiolectasis was seen in 50% versus 33% (P = 0.01 in the text; the table gives P = 0.02 for traction bronchiectasis for each observer).
  • The two most common abnormalities did not differ between scans. Centrilobular small dotlike or branching opacities were seen in 98% of 104 readings at baseline and 99% at follow-up; interstitial lines in 72% and 88%.
  • There was no significant increase in the extent of emphysema at follow-up.
  • Pleural plaques were present in 84 (81%) of 104 readings at baseline and 86 (83%) at follow-up. Diffuse pleural thickening was seen in 6 (6%) readings. All P values were above 0.10.
• The authors' conclusion: The authors concluded that the progression of parenchymal abnormality, seen in most patients at 3 to 5 years, was detected on careful side-by-side comparison but was mild. They found that it often did not change the Gamsu, Huuskonen or Sette classifications, and they said further studies are needed.
• Limitations the authors state:
  • Relatively small number of patients.
  • A high percentage of patients already had abnormal findings on the initial CT.
  • Relatively short follow-up time.
  • CT scans were performed on different scanners.
  • No histologic (tissue) correlation.
  • Because scans were taken at 10-mm intervals, small abnormalities could have been missed between sections.
  • The authors note that high-resolution CT findings of early asbestosis are neither sensitive nor specific.

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), CT Scan, Interstitial, Honeycombing, Asbestos Exposure.

Related studies

• Lung diffusing capacity relates better to short-term progression on HRCT abnormalities than spirometry in mild asbestosis — C.R. Nogueira, L.M. Nápolis, et al. (2011)
• Relationships (I) of International Classification of High-resolution Computed Tomography for Occupational and Environmental Respiratory Diseases with the ILO International Classification of Radiographs of Pneumoconioses for parenchymal abnormalities — T. Tamura, N. Suganuma, et al. (2015)
• Asbestos-related pleural and parenchymal fibrosis: detection with high-resolution CT — D.R. Aberle, G. Gamsu, et al. (1988)
• Asbestos-related pleural and parenchymal fibrosis: detection with high-resolution CT — T.C. McLoud (1989)
• Pleural plaques in asbestos-exposed workers: reproducibility of a new high-resolution CT visual semiquantitative measurement method — G.S. Meirelles, J.I. Kavakama, et al. (2006)
• High-resolution CT of benign asbestos-related diseases: clinical and radiographic correlation — D.R. Aberle, G. Gamsu, et al. (1988)

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