The validity of radiographic estimation of total lung capacity in patients with respiratory disease

Our plain-English summary of The validity of radiographic estimation of total lung capacity in patients with respiratory disease, by G.P. Pappas, C.A. Brodkin, L. Sheppard, et al (Chest, 1998).

The study

• Authors: G.P. Pappas, C.A. Brodkin, L. Sheppard, J. Balmes, M. Horike, S. Barnhart
• Journal: Chest
• Published: 1998;114(2):513-20
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Study Objective: To evaluate the validity of a state-of-the-art computerized planimetry technique for estimation of total lung capacity (TLC) from chest radiographs, when applied to patients with clinical lung disease receiving routine chest radiographs.

Design: Retrospective clinical survey.

Setting: An occupational medicine diagnostic clinic.

Patients: A convenience sample of 40 subjects with asbestos-related lung disease, 5 patients with nonasbestos-related restrictive defects, 15 subjects with occupational asthma, and 10 subjects with irritant tracheobronchitis.

Results: Estimation of TLC using state-of-the-art computerized algorithms demonstrated limited agreement with conventional measures of TLC when applied to patients with occupational lung disease receiving routine chest radiographs. The most pronounced differences occurred in patients with asbestos-related lung disease and restrictive defects, where the radiographic method of measurement significantly overestimated helium dilution TLC by 986 mL (r=0.73, p<0.001) and 1,135 mL (r=0.82, p<0.05), respectively. Good inspiratory effort was associated with significantly increased radiographic TLC relative to helium dilution TLC; however, radiographic features did not fully account for the observed differences between radiographic and helium dilution techniques.

Conclusions: Our findings suggest that this planimetric technique should not be used as a substitute for conventional measures of TLC in clinic populations receiving routine radiographs. The large diagnostic group specific mean differences observed between radiographic and conventional measures of TLC also suggest that this method is of limited utility in clinical evaluation of occupational lung disease.

In plain English

This retrospective clinical survey tested whether a computerized planimetry method estimating total lung capacity (TLC) from routine chest X-rays agreed with standard laboratory measurements. The authors studied 70 patients at a Seattle occupational medicine clinic, 1988 to 1994. Forty had asbestos-related lung disease, 5 had restrictive lung defects not related to asbestos, 15 had occupational asthma and 10 had irritant tracheobronchitis. In the asbestos group, the X-ray method gave values a mean 986 mL higher than helium dilution testing (r=0.73, p<0.001). In the restrictive group the mean difference was 1,135 mL (r=0.82, p<0.05). Mean differences were small in the asthma and irritant groups, but 44% of all patients had discrepancies of at least 1,000 mL. In an analysis accounting for diagnostic group, height and X-ray clarity, pleural plaques showed no significant additional influence on measured TLC by either method. Good inspiration on the X-ray was associated with higher TLC by both methods, significantly more so for the X-ray estimate. The authors concluded that the technique should not be used as a substitute for conventional TLC measurement in clinic patients receiving routine X-rays.

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: Retrospective clinical survey comparing a radiographic (computerized planimetry) estimate of total lung capacity with pulmonary function laboratory measurements
• Who was studied: Convenience sample of 70 patients (76 identified, 6 excluded) at the Harborview Medical Center Occupational and Environmental Medicine clinic, Seattle, 1988 to 1994: 40 with asbestos-related lung disease, 5 with nonasbestos restrictive defects, 15 with occupational asthma, 10 with irritant tracheobronchitis
• Exposure: Not an exposure study. Asbestos-related lung disease was defined as at least 6 months of occupational asbestos dust exposure, at least 15 years since first exposure, and either pleural thickening over 5 mm or ILO small-opacity profusion of 1/0 or greater. Fiber types were not specified. Patients worked as asbestos insulators, plumbers and pipefitters, shipyard workers, sheetmetal workers and plasterers.
• Main results:
  • Asbestos-related lung disease group (n=40): radiographic TLC overestimated helium dilution TLC by a mean of 986 mL (r=0.73, p<0.001)
  • Nonasbestos restrictive defect group (n=5): mean overestimate of 1,135 mL (r=0.82, p<0.05)
  • Occupational asthma and irritant tracheobronchitis groups: radiographic and helium dilution TLC were similar, with mean differences of -160 to -170 mL
  • All 70 patients combined: correlation of 0.66 and mean overestimate of 585 mL; 44% of all patients had discrepancies of at least 1,000 mL between the two measures
  • In the multivariate model, the asbestos-related lung disease group's radiographic TLC was estimated to be 1,116 mL higher than helium dilution after adjustment
  • Subset of 18 patients with both laboratory methods: helium dilution and plethysmography agreed closely (r=0.94); radiographic TLC correlated less well with helium dilution (r=0.67) and with plethysmography (r=0.63)
  • Good inspiration on the radiograph was associated with higher TLC by both the radiographic method (1,495 mL) and helium dilution (921 mL); the association was significantly larger for the radiographic measure (p=0.04)
  • Pleural plaques on the chest radiograph had no significant influence on TLC by either method, above the effects of diagnostic group, height and radiograph clarity score
  • Only 2 (3%) of the 70 radiographs showed good inspiration, no rotation, perfect clarity and no pleural disease
• The authors' conclusion: The authors concluded that this planimetric technique should not be used as a substitute for conventional TLC measurement in clinic populations receiving routine radiographs
• Limitations the authors state:
  • Radiographs of asbestos-exposed subjects were read by a reader trained in the ILO system, but not by a certified B reader
  • Routine radiographs were taken without special effort to ensure full inspiration; research-protocol radiographs may use more rigorous techniques and may not share these limitations
  • Correlation estimates varied across groups partly because of differences in sample sizes and TLC levels
  • Only limited data were available for patients with restrictive defects
  • Data from clinically evaluated patients may have quality-control limitations not present in epidemiologic studies

Topics

Medical terms in this study, explained in our Lexicon: Total Lung Capacity (TLC), Chest X-Ray, Occupational Lung Disease.

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