Diagnosis of asbestosis by a time expanded wave form analysis, auscultation and high resolution computed tomography: a comparative study

Our plain-English summary of Diagnosis of asbestosis by a time expanded wave form analysis, auscultation and high resolution computed tomography: a comparative study, by N. al Jarad, B. Strickland, G. Bothamley, et al (Thorax, 1993).

The study

• Authors: N. al Jarad, B. Strickland, G. Bothamley, S. Lock, R. Logan-Sinclair, R.M. Rudd
• Journal: Thorax
• Published: 1993;48(4):347-53
• Cited by: 27 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Crackles are a prominent clinical feature of asbestosis and may be an early sign of the condition. Auscultation, however, is subjective and interexaminer disagreement is a problem. Computerised lung sound analysis can visualise, store, and analyse lung sounds and disagreement on the presence of crackles is minimal. High resolution computed tomography (HRCT) is superior to chest radiography in detecting early signs of asbestosis. The aim of this study was to compare clinical auscultation, time expanded wave form analysis (TEW), chest radiography, and HRCT in detecting signs of asbestosis in asbestos workers.

Methods: Fifty three asbestos workers (51 men and two women) were investigated. Chest radiography and HRCT were assessed by two independent readers for detection of interstitial opacities. HRCT was performed in the supine position with additional sections at the bases in the prone position. Auscultation for persistent fine inspiratory crackles was performed by two independent examiners unacquainted with the diagnosis. TEW analysis was obtained from a 33 second recording of lung sounds over the lung bases. TEW and auscultation were performed in a control group of 13 subjects who had a normal chest radiograph. There were 10 current smokers and three previous smokers. In asbestos workers the extent of pulmonary opacities on the chest radiograph was scored according to the International Labour Office (ILO) scale. Patients were divided into two groups: 21 patients in whom the chest radiograph was > 1/0 (group 1) and 32 patients in whom the chest radiograph was scored < or = 1/0 (group 2) on the ILO scale.

Results: In patients with an ILO score of < or = 1/0 repetitive mid to late inspiratory crackles were detected by auscultation in seven (22%) patients and by TEW in 14 (44%). HRCT detected definite interstitial opacities in 11 (34%) and gravity dependent subpleural lines in two (6%) patients. All but two patients with evidence of interstitial disease or gravity dependent subpleural lines on HRCT had crackles detected by TEW. In patients with an ILO score of > 1/0 auscultation and TEW revealed mid to late inspiratory crackles in all patients, whereas HRCT revealed gravity dependent subpleural lines in one patient and signs of definite interstitial fibrosis in the rest. In normal subjects crackles different from those detected in asbestosis were detected by TEW in three subjects but only in one subject by auscultation. These were early, fine inspiratory crackles.

Conclusion: Mid to late inspiratory crackles in asbestos workers are detected by TEW more frequently than by auscultation. Signs of early asbestosis not apparent on the plain radiograph are detected by TEW and HRCT with similar frequency. off

In plain English

This study compared four ways of detecting asbestosis in 53 asbestos workers (51 men, two women). The four methods were listening to the chest by two examiners (auscultation), a computerised lung sound recording called time expanded wave form analysis (TEW), chest radiographs scored on the International Labour Office (ILO) scale, and high resolution computed tomography (HRCT). The workers had been laggers, asbestos cutters, millers and spinners, or, for the two women, cleaners of asbestos-contaminated clothes. The article did not name fiber types. In the 21 workers whose radiographs scored above 1/0, auscultation and TEW found crackles in every one. Among the 32 workers scored 1/0 or below, auscultation found crackles in 7 (22%) and TEW in 14 (44%), a difference with p less than 0.04. HRCT showed pulmonary opacities in 11 (34%) of these 32. In 13 control subjects with no asbestos exposure, TEW found fine early inspiratory crackles in three, and auscultation found them in one. The authors concluded that TEW and HRCT detected signs of early asbestosis not visible on plain radiographs with similar frequency. They noted that HRCT features overlap with cryptogenic fibrosing alveolitis and that TEW is probably less specific.

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: Comparative diagnostic study: auscultation, TEW, chest radiography and HRCT were each applied to the same asbestos workers, and results were compared using McNemar's test. A small control group without asbestos exposure had auscultation and TEW only.
• Who was studied: 53 asbestos workers (51 men, two women) who presented for assessment of possible asbestos-related disease, at hospitals in London (author affiliations). They were divided into group 1 (21 patients, ILO chest radiograph score above 1/0) and group 2 (32 patients, score 1/0 or below). There were also 13 control subjects (four women, nine men; mean age 49, range 33 to 64; 10 current and three previous smokers) with normal chest radiographs and no asbestos exposure. Study dates were not given.
• Exposure: Occupational asbestos exposure with a mean duration of 11.3 years (range 1 to 35). 34 workers were in the lagging industry and 17 did asbestos cutting, milling and spinning. The two women were exposed for more than 20 years through cleaning clothes contaminated with asbestos. Fiber types were not specified.
• Main results:
  • Group 1 (ILO score above 1/0, 21 patients): auscultation and TEW detected crackles in all patients.
  • Group 1: HRCT showed definite interstitial opacities consistent with asbestosis in all but one patient. That patient had gravity dependent subpleural lines.
  • Group 2 (ILO score 1/0 or below, 32 patients): TEW detected fine mid to late inspiratory crackles in 14 (44%). By radiograph score, TEW found crackles in 3 of 17 scored 0/0 (18%), 4 of 4 scored 0/1 (100%), and 7 of 11 scored 1/0 (64%).
  • Group 2: auscultation detected crackles in 7 (22%). TEW detected crackles more frequently than auscultation (p less than 0.04, McNemar's test).
  • Group 2: HRCT detected pulmonary opacities in 11 of 32 (34%). By radiograph score, these were 1 of 17 scored 0/0 (6%), 2 of 4 scored 0/1 (50%), and 8 of 11 scored 1/0 (73%).
  • Group 2: HRCT detected gravity dependent discrete subpleural lines in two (6%) patients.
  • In group 2, TEW detected crackles in all but two patients in whom HRCT showed asbestosis.
  • Group 2 patients with vital capacity above 80% of predicted (n = 21): auscultation found crackles in four (19%) and TEW in eight (38%). HRCT showed interstitial fibrosis in six (29%) and gravity dependent subpleural lines in two (10%).
  • 13 control subjects: TEW detected fine early inspiratory crackles in three, and auscultation detected crackles in only one.
  • Agreement between examiners on definitive signs of asbestosis on the chest radiograph and HRCT was more than 90%.
  • Agreement between examiners on the presence or absence of crackles by auscultation was relatively poor (71%).
• The authors' conclusion: The authors concluded that TEW detected lung crackles in asbestos workers more frequently than auscultation. They also concluded that TEW and HRCT detected signs of early asbestosis not apparent on plain radiography with similar frequency.
• Limitations the authors state:
  • HRCT opacities were not entirely specific for asbestosis; the authors had previously shown overlap with cryptogenic fibrosing alveolitis.
  • TEW is probably less specific than HRCT.
  • HRCT was not performed in the control group.
  • Agreement between examiners on crackles detected by TEW was not examined in this study, though it had been investigated previously.
  • A chest radiograph classified as 1/0 could be considered abnormal, and observers disagree considerably on the 1/0 score.

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), Interstitial, Chest X-Ray, Subpleural Curvilinear Line, Interstitial Fibrosis.

Related studies

• Lung crackle characteristics in patients with asbestosis, asbestos-related pleural disease and left ventricular failure using a time-expanded waveform analysis--a comparative study — N. al Jarad, S.W. Davies, et al. (1994)
• 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)
• The comparison of high-resolution computed tomography findings in asbestosis and idiopathic pulmonary fibrosis — M. Akira, K. Morinaga (2016)
• 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)
• Conventional and high resolution computed tomography in the diagnosis of asbestos-related diseases — D.A. Lynch, G. Gamsu, et al. (1989)
• High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs — C.A. Staples, G. Gamsu, et al. (1989)

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