Comparison of digital with film radiographs for the classification of pneumoconiotic pleural abnormalities

Our plain-English summary of Comparison of digital with film radiographs for the classification of pneumoconiotic pleural abnormalities, by T.C. Larson, D.B. Holiday, V.C. Antao, et al (Academic Radiology, 2012).

The study

• Authors: T.C. Larson, D.B. Holiday, V.C. Antao, J. Thomas, G. Pinheiro, V. Kapil, A. Franzblau
• Journal: Academic Radiology
• Published: 2012;19(2):131-40
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Rationale And Objectives: Analog film radiographs are typically used to classify pneumoconiosis to allow comparison with standard film radiographs. The aim of this study was to determine if digital radiography is comparable to film for the purpose of classifying pneumoconiotic pleural abnormalities.

Materials And Methods: Subjects were 200 asbestos-exposed patients, from whom digital and film chest radiographs were obtained along with chest high-resolution computed tomographic scans. Using a crossover design, radiographs were independently read on two occasions by seven readers, using conventional International Labour Organization standards for film and digitized standards for digital. High-resolution computed tomographic scans were read independently by three readers. Areas under the receiver-operating characteristic curves were calculated using high-resolution computed tomographic ratings as the gold standard for disease status. Mixed linear models were fit to estimate the effects of order of presentation, occasion, and modality, treating the seven readers as a random effect. Comparing digital and film radiography for each reader and occasion, crude agreement and agreement beyond chance (κ) were also calculated.

Results: The linear models showed no statistically significant sequence effect for order of presentation (P = .73) or occasion (P = .28). Most important, the difference between modalities was not statistically significant (digital vs film, P = .54). The mean area under the curve for film was 0.736 and increased slightly to 0.741 for digital. Mean crude agreement for the presence of pleural abnormalities consistent with pneumoconiosis across all readers and occasions was 78.3%, while the mean κ value was 0.49.

Conclusions: These results indicate that digital radiography is not statistically different from analog film for the purpose of classifying pneumoconiotic pleural abnormalities, when appropriate standards are used.

Published by Elsevier Inc.

In plain English

This study compared digital with film chest X-rays for classifying pleural abnormalities consistent with pneumoconiosis. The 200 subjects were Libby, Montana, clinic patients exposed to asbestos-contaminated vermiculite formerly mined near the town. Enrollment and imaging took place in 2007 and 2008. Each had film and digital X-rays taken within 3 days of each other, plus an earlier high-resolution CT scan. Six certified B readers read every X-ray on two occasions, and a seventh read each once. Three thoracic radiologists read the CT scans; a pleural abnormality seen by at least two served as the reference standard. By that standard, 110 subjects (55.0%) had a pleural abnormality. Accuracy measured against CT did not differ significantly between digital and film (P = .54). The mean area under the curve was 0.736 for film and 0.741 for digital. For the same reader and occasion, digital and film readings agreed on whether a pleural abnormality was present 78.3% of the time on average. The authors concluded that digital radiography was not statistically different from film for this purpose when appropriate standards are used.

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: Diagnostic comparison study with a crossover reading design. Film and digital radiographs were read by seven B readers: six read them on two occasions and one on a single occasion. High-resolution CT (HRCT) served as the gold standard.
• Who was studied: 200 asbestos-exposed patients of the Center for Asbestos Related Disease clinic in Libby, Montana, recruited in 2007 and 2008. 143 (71.5%) were men and the median age was 63 years. Radiographs were read by 7 B readers and HRCT scans by 3 thoracic radiologists.
• Exposure: Exposure to asbestos-contaminated vermiculite mined near Libby. Predominant sources were occupational for 46 subjects (23.0%), household contact for 51 (25.5%), and presumed environmental only for 103 (51.5%). The comparison itself was between imaging methods: film versus digital radiographs.
• Main results:
  • By HRCT, 110 of the 200 subjects (55.0%) had a pleural abnormality seen by at least two of the three radiologists. This served as the gold standard.
  • Accuracy against the HRCT gold standard (area under the curve) did not differ significantly between digital and film radiographs (P = .54).
  • The mean area under the curve was 0.736 for film and 0.741 for digital.
  • Neither the order in which film and digital images were read (P = .73) nor the reading occasion (P = .28) had a statistically significant effect.
  • Comparing digital with film readings by the same reader on the same occasion, mean crude agreement on whether any pleural abnormality was present was 78.3% (range 65.5% to 87.0%). The mean kappa was 0.49, which the authors described as moderate.
  • Across all readings, any pleural abnormality was recorded slightly more often on film (56.2%) than on digital (54.3%). This difference was not statistically significant (P = .17).
  • Image quality was rated 'good' more often for digital readings (66.0%) than for film readings (61.6%), a significant difference (P less than .01).
• The authors' conclusion: The authors concluded that digital radiography is not statistically different from analog film for classifying pneumoconiotic pleural abnormalities, when appropriate standards are used. They also recommended further research, including an equivalence study.
• Limitations the authors state:
  • Real-world reading conditions may not have been reproduced, because the reading environment and image processing were tightly controlled.
  • Some HRCT scans used as the gold standard were taken 1 to 2 years before the radiographs, which may have caused some misclassification of disease status.
  • Kappa analysis is considered controversial by some, partly because it can give counterintuitive results.
  • Many subjects were obese. Extrapleural fat can mimic pleural plaque, so plaque may have been misclassified.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana

All asbestos mines

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: Pneumoconiosis, Chest X-Ray.

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