Diagnostic Performance of Ultra-Low-Dose Computed Tomography for Detecting Asbestos-Related Pleuropulmonary Diseases: Prospective Study in a Screening Setting

Our plain-English summary of Diagnostic Performance of Ultra-Low-Dose Computed Tomography for Detecting Asbestos-Related Pleuropulmonary Diseases: Prospective Study in a Screening Setting, by M. Schaal, F. Severac, A. Labani, et al (PloS One, 2016).

The study

• Authors: M. Schaal, F. Severac, A. Labani, M.Y. Jeung, C. Roy, M. Ohana
• Journal: PloS One
• Published: 2016;11(12):e0168979
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To evaluate the diagnostic performance of Ultra-Low-Dose Chest CT (ULD CT) for the detection of any asbestos-related lesions (primary endpoint) and specific asbestos-related abnormalities, i.e. non-calcified and calcified pleural plaques, diffuse pleural thickening, asbestosis and significant lung nodules (secondary endpoints).

Material And Methods: 55 male patients (55.7±8.1 years old) with occupational asbestos exposure for at least 15 years and where CT screening was indicated were prospectively included. They all underwent a standard unenhanced chest CT (120kV, automated tube current modulation), considered as the reference, and an ULD CT (135kV, 10mA), both with iterative reconstruction. Two chest radiologists independently and blindly read the examinations, following a detailed protocol. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy and error rate of ULD CT were calculated using the exact method of Pearson with a confidence interval of 95%.

Results: Radiation dose was 17.9±1.2mGy.cm (0.25mSv) for the ULD-CT versus 288.8 ±151mGy.cm (4mSv); p <2.2e-16. Prevalence of abnormalities was 20%. The ULD CT's diagnostic performance in joint reading was high for the primary endpoint (sensitivity = 90.9%, specificity = 100%, positive predictive value = 100%, negative predictive value = 97.8%), high for lung nodules, diffuse pleural thickening and calcified pleural plaques (sensitivity, specificity, PPV and NPV = 100%) and fair for asbestosis (sensitivity = 75%, specificity = 100%, PPV = 00%, NPV = 98.1%). Intra-reader accuracy between the ULD CT and the reference CT for the primary endpoint was 98% for the senior and 100% for the junior radiologist. Inter-reader agreement for the primary endpoint was almost perfect (Cohen's Kappa of 0.81).

Conclusion: ULD CT in the screening of asbestos exposure related diseases has 90.9% sensitivity and 100% specificity, and could therefore be proposed as a first line examination.

In plain English

This prospective study in France, run from July 2013 to May 2014, tested whether an ultra-low-dose (ULD) chest CT scan could find asbestos-related chest disease as well as a standard-dose CT. It included 55 men with at least 15 years of work exposure to asbestos (average 19.6 years). The article does not name fiber types. Each man had both scans. Two radiologists read them separately, and the standard scan served as the reference. Average effective radiation dose was 0.25 mSv for the ULD scan versus 4 mSv for the standard scan. Eleven of the 55 men (20%) had asbestos-related abnormalities. The ULD scan found 10 of them and gave no false positives, for a sensitivity of 90.9%, specificity of 100% and negative predictive value of 97.8%. The missed case was subtle early asbestosis, and the ULD scan detected 3 of the 4 asbestosis cases. Image quality was lower on the ULD scan, but readers' confidence did not differ significantly. The authors noted the small sample and the use of a single scanner. They concluded that ULD CT could be proposed as a first-line screening test, with a standard CT only in doubtful or positive cases.

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 diagnostic accuracy study: each patient had both an ultra-low-dose chest CT and a standard-dose chest CT, and the ULD scan was compared against the joint reading of the standard scan as the reference
• Who was studied: 55 men (mean age 55.7 years, range 44 to 82) referred to the authors' radiology department in France for CT screening for asbestos-related disease, July 2013 to May 2014. Of 61 referred, 4 refused and 2 could not lie in the required position. 49% were active smokers.
• Exposure: Occupational asbestos exposure for at least 15 years (inclusion criterion). Average cumulative exposure was 19.6 years, with at least 12 years between end of exposure and screening. Fiber types, products and jobs are not specified.
• Main results:
  • Radiation dose: the ULD scan averaged a dose-length product of 17.9 mGy.cm (effective dose 0.25 mSv), versus 288.8 mGy.cm (4 mSv) for the standard scan. The authors describe this as a dose divided by 16.
  • On the reference standard scan, 11 of 55 patients (20%) had asbestos-related abnormalities overall
  • For detecting any asbestos-related abnormality, the ULD scan gave 44 true negatives, 10 true positives, 1 false negative and no false positives among the 55 patients. Sensitivity was 91% and specificity 100%.
  • For the primary endpoint, positive predictive value was 100%, negative predictive value 97.8% and sensitivity 90.9%
  • The single missed case was subtle early asbestosis seen on the standard scan but not on the ULD scan (a 47-year-old man with 15 years of exposure)
  • For interstitial changes suggesting asbestosis, the ULD scan's sensitivity was 75% (3 of 4 cases)
  • Solid lung nodules larger than 5 mm, and calcified pleural plaques, were detected on the ULD scan by both readers in every case
  • Agreement between each reader's ULD reading and their own standard-scan reading for the primary endpoint was 98.2% for the senior reader and 100% for the junior reader
  • Agreement between the two readers on the ULD scan for the primary endpoint had a Cohen's Kappa of 0.810, which the authors describe as almost perfect. The Kappa was 0.756 on the standard scan.
  • Subjective image quality was lower for the ULD scan (3.98 out of 5) than for the reference scan (4.83), a statistically significant difference (p less than 0.001). Image noise was also higher on the ULD scan (63 versus 48 HU).
  • Readers' average diagnostic confidence was 4.55 out of 5 for the ULD scan and 4.52 for the standard scan, with no significant difference (p = 0.6075)
• The authors' conclusion: The authors concluded that ULD CT could be proposed as a first-line screening test for asbestos-related pleuropulmonary disease, followed by a full-dose CT only in doubtful or positive cases
• Limitations the authors state:
  • Small sample size (55 patients)
  • Because of the small sample, a non-inferiority threshold of 10% was used. The authors state that a more classical 5% threshold would have required 140 patients.
  • Because asbestosis was uncommon, ULD sensitivity and PPV for asbestosis remain limited
  • All scans were done on one manufacturer's machine with one image reconstruction algorithm (vendor specific)
  • The proposed screening method would require a radiologist to be present during scanning, which is difficult in some countries

Topics

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

Medical terms in this study, explained in our Lexicon: Low-Dose CT Screening, Pleural Plaques, Diffuse Pleural Thickening, Asbestos Exposure, confidence interval.

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• The usefulness of computed tomography in detecting asbestos-related pleural abnormalities in people who had indeterminate chest radiographs: the Libby, MT, experience — O.I. Muravov, W.E. Kaye, et al. (2005)
• Low-dose computed tomography screening for lung cancer and pleural mesothelioma in an asbestos-exposed population: baseline results of a prospective, nonrandomized feasibility trial--an Alpe-adria Thoracic Oncology Multidisciplinary Group Study (ATOM 002) — G. Fasola, O. Belvedere, et al. (2007)
• Yield of Low-Dose Computerized Tomography Screening for Lung Cancer in High-Risk Workers: The Case of 7189 US Nuclear Weapons Workers — S.B. Markowitz, A. Manowitz, et al. (2018)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)

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