The detection of thoracic abnormalities using posterior-anterior (PA) vs PA and oblique roentgenograms

Our plain-English summary of The detection of thoracic abnormalities using posterior-anterior (PA) vs PA and oblique roentgenograms, by R.B. Reger, R.G. Ames, J.A. Merchant, et al (Chest, 1982).

The study

• Authors: R.B. Reger, R.G. Ames, J.A. Merchant, P.P. Polakoff, E.N. Sargent, M. Silbiger, P. Whittlesey
• Journal: Chest
• Published: 1982;81(3):290-5
• Cited by: 20 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. 000705).

Abstract

A reading trial was conducted as part of the 1978 Bay Area Asbestos Screening Project to evaluate the utility of adding oblique-view roentgenograms to standard posterior-anterior (PA) views. Chest films from a sample of 555 workers with histories of long-term asbestos exposure were read twice as PA and twice as PA + oblique sets, providing a basis for assessing reliability through intrareader, interreader, and intermethod agreement. The ancillary use of oblique view films resulted in higher rates of detection of asbestos-related abnormalities than with PA films alone, but the increased rates were gained at the expense of reliability in the interpretation process. Depending on the source of this unreliability, which requires further study, different remedial actions might be indicated. A reader's lack of experience could indicate the need for additional training, the use of several readers, an average over several reader judgements, or the development of standards for evaluating obliques. If, on the other hand, no way is found to reduce the unreliability, the use of oblique films in routine screening programs ought to be discouraged on the basis of measurement theory, since reliability is a prerequisite to validity.

In plain English

This reading trial was part of the 1978 Bay Area Asbestos Screening Project in San Francisco. It used chest X-rays of 555 workers, chosen for acceptable to excellent film quality from 2,266 volunteers, almost all with long-term asbestos exposure. Three experienced radiologists each read every worker's films four times. Twice they used the standard posterior-anterior (PA) chest view alone, and twice the PA view plus right and left oblique (angled) views. With four of six readings counted as positive, oblique views gave detection rates 22 percent higher for pleural thickening, 103 percent higher for pleural plaques and 93 percent higher for small lung opacities. For pleural thickening, the increase occurred only in workers 30 or more years from first exposure. Agreement between readers, measured by a statistic called kappa, fell 30 to 50 percent with oblique views. Readers' agreement with their own earlier readings changed inconsistently: on average it fell slightly for pleural thickening but rose for plaques and small opacities. The authors concluded that oblique views made readings less consistent. They did not know which workers truly had these abnormalities.

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: Reading trial (methodologic study of the reliability of chest X-ray interpretation): each set of films was read four times by each of three radiologists, twice as PA films only and twice as PA plus oblique sets
• Who was studied: Chest films of 555 workers, selected for acceptable to excellent film quality from the 2,266 media-recruited volunteers in the 1978 Bay Area Asbestos Screening Project (San Francisco); read by three radiologists experienced in reading films of asbestos-exposed workers
• Exposure: History of long-term asbestos exposure (fiber types not specified). The comparison studied was standard PA chest films alone versus PA films plus right and left 45-degree oblique films.
• Main results:
  • Detection rates, with four of six readings positive as the criterion, among 547 cases with known time since first exposure. Pleural thickening: 16.3% with PA only vs 19.9% with PA plus oblique. Pleural plaques: 12.8% vs 26.0%. Profusion of small opacities: 6.9% vs 13.3%. These correspond to detection rates 22, 103 and 93 percent higher with oblique films.
  • For pleural thickening, the higher detection rate with oblique films applied only to the group with 30 or more years since first exposure (19.5% PA only vs 26.2% PA plus oblique). In the group with less than 15 years it was 9.3% vs 4.7%.
  • With a less strict criterion (three of six readings positive), the increases with oblique films were 28 percent (pleural thickening), 79 percent (pleural plaques) and 44 percent (small opacities).
  • Detection rose with time since first exposure to asbestos for all three abnormalities, under both reading procedures.
  • Agreement of readers with their own earlier readings (average kappa) was inconsistent between methods. Pleural thickening fell from .67 (PA only) to .64 (PA plus oblique), a change of -4.5%. Pleural plaques rose from .63 to .73 (+15.9%). Small opacities rose from .47 to .70 (+48.9%).
  • Agreement between readers beyond chance ranged from kappa .10 to .43. It dropped by 30 to 50 percent with oblique films: by -42.0% for pleural thickening, -30.0% for pleural plaques and -50.0% for small opacities.
  • Agreement between PA-only and PA-plus-oblique readings (average kappa) was lowest for pleural plaques (.39), .43 for pleural thickening and highest for small opacities (.47). It varied markedly by reader.
  • Most changes between methods were shifts from no involvement to involvement or suspicion of involvement. The weighted average share of changes that were increases was 56.2% for pleural thickening, 68.0% for pleural plaques and 79.4% for small opacities.
• The authors' conclusion: The authors concluded that adding oblique films gave much higher detection rates but less consistent measurement, so reliability suffered and validity was in question. They suggested possible remedies such as training, several readers or standards for reading oblique films. If the unreliability cannot be reduced, they concluded that routine use of oblique films in screening for asbestos-related disease may be questionable.
• Limitations the authors state:
  • The true presence or absence of pleural thickening, plaques or small opacities was not known, so sensitivity, specificity and false-positive and false-negative rates could only be speculated about.
  • Many screening films were overexposed because of mobile unit equipment problems, so the sample was limited to films of acceptable quality. The authors found no evidence that overexposure was related to the workers' health status.
  • The source of the unreliability with oblique films was not resolved (for example, reader inexperience, lack of standards, or the films themselves).

Topics

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Asbestos Exposure.

Related studies

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