Lung diffusing capacity relates better to short-term progression on HRCT abnormalities than spirometry in mild asbestosis

Our plain-English summary of Lung diffusing capacity relates better to short-term progression on HRCT abnormalities than spirometry in mild asbestosis, by C.R. Nogueira, L.M. Nápolis, E. Bagatin, et al (American Journal of Industrial Medicine, 2011).

The study

• Authors: C.R. Nogueira, L.M. Nápolis, E. Bagatin, M. Terra-Filho, N.L. Müller, C.I. Silva, R.T. Rodrigues, J.A. Neder, L.E. Nery
• Journal: American Journal of Industrial Medicine
• Published: 2011;54(3):185-93
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Pulmonary function tests (PFT), particularly spirometry and lung diffusing capacity for carbon monoxide (DL(CO) ), have been considered useful methods for the detection of the progression of interstitial asbestos abnormalities as indicated by high-resolution computed tomography (HRCT). However, it is currently unknown which of these two tests correlates best with anatomical changes over time.

Methods: In this study, we contrasted longitudinal changes (3-9 years follow-up) in PFTs at rest and during exercise with interstitial abnormalities evaluated by HRCT in 63 ex-workers with mild-to-moderate asbestosis.

Results: At baseline, patients presented with low-grade asbestosis (Huuskonen classes I-II), and most PFT results were within the limits of normality. In the follow-up, most subjects had normal spirometry, static lung volumes and arterial blood gases. In contrast, frequency of DL(CO) abnormalities almost doubled (P < 0.05). Twenty-three (36.5%) subjects increased the interstitial marks on HRCT. These had significantly larger declines in DL(CO) compared to patients who remained stable (0.88 vs. 0.31 ml/min/mm Hg/year and 3.5 vs. 1.2%/year, respectively; P < 0.05). In contrast, no between-group differences were found for the other functional tests, including spirometry (P > 0.05).

Conclusions: These data demonstrate that the functional consequences of progression of HRCT abnormalities in mild-to-moderate asbestosis are better reflected by decrements in DL(CO) than by spirometric changes. These results might have important practical implications for medico-legal evaluation of this patient population.

Copyright © 2010 Wiley-Liss, Inc.

In plain English

This study followed 63 former workers with mild-to-moderate asbestosis: 46 asbestos-cement workers and 17 chrysotile asbestos miners. Their high-resolution CT (HRCT) lung scans showed mild scarring, and they were retested 3 to 9 years apart. The authors compared scan changes with breathing tests, including spirometry and DLCO, a measure of how well the lungs pass gas into the blood. On follow-up, 23 workers (36.5%) showed worse scarring on HRCT. Their DLCO fell faster each year than in those whose scans stayed stable: 0.88 vs. 0.31 ml/min/mm Hg per year, or 3.5% vs. 1.2% per year (P less than 0.05). Spirometry did not differ significantly between the two groups. Across the whole group, abnormal DLCO results rose from 13 of 60 to 22 of 60. The authors concluded that DLCO is a key test for following these patients over time. They noted that smoking might explain some of the decline, and that tests were done at only two time points.

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 longitudinal study comparing changes in lung function tests with changes in HRCT abnormalities over 3–9 years of follow-up
• Who was studied: 63 ex-workers with mild-to-moderate asbestosis: 46 asbestos-cement workers and 17 chrysotile asbestos miners, all with HRCT scans showing mild interstitial abnormalities
• Exposure: Occupational asbestos exposure in asbestos-cement work and in chrysotile asbestos mining. The fiber type is stated only for the miners (chrysotile).
• Main results:
  • At baseline, 47 of the 63 subjects (74.6%) had normal spirometry, 13 had obstructive impairment and 3 had restrictive impairment
  • 23 subjects (36.5%) progressed on HRCT: 14 scans changed from Huuskonen grade I to II and 9 from grade II to III
  • Subjects whose HRCT worsened had larger yearly DLCO declines than subjects who remained stable: 0.88 vs. 0.31 ml/min/mm Hg/year, and 3.5%/year vs. 1.2%/year (P < 0.05)
  • No significant differences were found in spirometric variables, resting PaO2 or exercise P(A-a)O2 between subjects who progressed on HRCT and those who did not
  • In the whole group, abnormal DLCO results rose from 13/60 (21.7%) at baseline to 22/60 (36.7%) at follow-up
  • In a post hoc analysis, subjects whose DLCO fell by more than 0.85 ml/min/mm Hg/year more often had worsening HRCT than those with smaller declines (57% vs. 27%)
  • Chest X-ray profusion was not significantly associated with spirometric or DLCO measurements
• The authors' conclusion: The authors concluded that, because DLCO was impaired in a substantial proportion of cases with normal spirometry, DLCO is a key pulmonary function test for following these subjects over time
• Limitations the authors state:
  • The authors could not rule out that some of the decline in lung function was due to smoking
  • Lung function tests were measured at only two time points
  • The Huuskonen HRCT scoring scheme may not be sensitive enough to detect progression
  • There was substantial loss to follow-up for lung function tests other than spirometry and DLCO
  • The follow-up time may have been too short to detect significant changes
  • Survival bias may have influenced the results, though the authors considered this unlikely to be serious
  • Asbestosis was not confirmed by tissue examination

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile.

Medical terms in this study, explained in our Lexicon: Diffusing Capacity (DLCO), High-Resolution CT (HRCT), Spirometry, Pulmonary Function Test (PFT), Interstitial.

Related studies

• Asbestos-related disease: progression of parenchymal abnormalities on high-resolution CT — C.I. Silva, N.L. Müller, et al. (2008)
• Diffusing capacity and forced vital capacity in 5,003 asbestos-exposed workers: relationships to interstitial fibrosis (ILO profusion score) and pleural thickening — A. Miller, R. Warshaw, et al. (2013)
• Reduced diffusing capacity as an isolated finding in asbestos- and silica-exposed workers — J.G. Garcia, D.E. Griffith, et al. (1990)
• Association between neutrophil concentration in bronchoalveolar lavage fluid and recent losses in diffusing capacity in men formerly exposed to asbestos — M.R. Cullen, W.W. Merrill (1992)
• Biphasic lung diffusing capacity: detection of early asbestos induced changes in lung function — Z. Dujić, J. Tocilj, et al. (1992)
• Single breath diffusing capacity in the industrial setting — B. Make, A. Miller, et al. (1982)

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