Chest

Chest

Volume 134, Issue 6, December 2008, Pages 1183-1191
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Original Research
Asthma
Airway Remodeling Measured by Multidetector CT Is Increased in Severe Asthma and Correlates With Pathology

https://doi.org/10.1378/chest.07-2779Get rights and content

Background

To prospectively apply an automated, quantitative three-dimensional approach to imaging and airway analysis to assess airway remodeling in asthma patients.

Methods

Using quantitative software (Pulmonary Workstation, version 0.139; VIDA Diagnostics; Iowa City, IA) that enables quantitative airway segment measurements of low-dose, thin-section (0.625 to 1.25 mm), multidetector-row CT (MDCT) scans, we compared airway wall thickness (WT) and wall area (WA) in 123 subjects participating in a prospective multicenter cohort study, the National Institutes of Health Severe Asthma Research Program (patients with severe asthma, n = 63; patients with mild-to-moderate asthma, n = 35); and healthy subjects, n = 25). A subset of these subjects underwent fiberoptic bronchoscopy and endobronchial biopsies (n = 32). WT and WA measurements were corrected for total airway diameter and area: WT and WA, respectively.

Results

Subjects with severe asthma had a significantly greater WT% than patients with mild-to-moderate asthma and healthy subjects (17.2 ± 1.5 vs 16.5 ± 1.6 [p = 0.014] and 16.3 ± 1.2 [p = 0.031], respectively) and a greater WA percentage (WA%) compared to patients with mild-to-moderate asthma and healthy subjects (56.6 ± 2.9 vs 54.7 ± 3.3 [p = 0.005] and 54.6 ± 2.4 [p = 0.003], respectively). Both WT% and WA% were inversely correlated with baseline FEV1 percent predicted (r = −0.39, p < 0.0001 and r = −0.40, p < 0.0001, respectively) and positively correlated with response to a bronchodilator (r = 0.28, p = 0.002 and r = 0.35, p < 0.0001, respectively). The airway epithelial thickness measure on the biopsy sample correlated with WT% (r = 0.47; p = 0.007) and WA% (r = 0.52; p = 0.003). In the same individual, there is considerable regional heterogeneity in airway WT.

Conclusion

Patients with severe asthma have thicker airway walls as measured on MDCT scan than do patients with mild asthma or healthy subjects, which correlates with pathologic measures of remodeling and the degree of airflow obstruction. MDCT scanning may be a useful technique for assessing airway remodeling in asthma patients, but overlap among the groups limits the diagnostic value in individual subjects.

Section snippets

Study Design

As part of the Severe Asthma Research Program (SARP) at the National Institutes of Health, a prospective cohort of subjects, following informed consent, underwent detailed testing and MDCT scanning using a standardized protocol that was developed by the SARP.17 MDCT scan data were analyzed and compared in a total of 123 subjects, as follows: patients with severe asthma, n = 63; patients with mild-to-moderate asthma, n = 35; healthy subjects, n = 25. In a subset of patients who underwent airway

Demographics

The characteristics of the subjects in our study (Table 1) demonstrated that those with severe persistent asthma, on average, were older, reported more frequent symptoms of allergies, and had elevated levels of IgE, increased airway hyperresponsiveness, and decreased baseline FEV1 percent predicted compared to patients with mild-to-moderate asthma and healthy subjects. Subjects in the biopsy subset were representative of the overall cohort (Table 1) with the exception that patients with

Discussion

Airway remodeling describes structural changes that in the asthmatic airway collectively result in thickening of the airway wall.2, 3, 8, 9 CT imaging of the airways is being developed as a technique to study airway remodeling in vivo. Multiple studies5, 6, 7, 8, 13, 14, 15 have documented increased airway WT in asthma using CT. Most of these studies5, 13, 14, 15 employed manual tracing methods, using either manual or digital measurement of airway dimensions. These previous studies using manual

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    This research was supported by National Institutes of Health grants HL69149, HL64368, HL69349, HL69170, HL-69155, HL69174, HL69130, HL69167, HL69116, and HL69174–05.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).

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    Copyright © 2008 The American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.