Although clinicians rely on spirometry to diagnose and manage patients with COPD, this diagnostic tool does not provide estimates of regional airway or parenchymal abnormalities. This limitation includes a lack of information on the small airways where COPD onset and progression are thought to commence.
Studies have shown that total airway count (TAC) and airway wall thickness measured using CT can provide important information regarding the severity and progression of COPD. What is lacking is longitudinal information on how TAC and airway wall thickness change in patients with COPD over time and how these changes can provide insight into disease progression.
To this end, Grace Parraga, PhD, MsC, BSc, and colleagues assembled a prospective convenience sample study focused on former smokers to observe whether CT airway measurements in former smokers would decline despite a lack of worsening FEV1 or other evidence of worsening COPD. Dr. Parraga discussed the findings of this study with Physician’s Weekly.
Why did you feel this topic needed exploration?
We understand that some COPD patients worsen, in terms of symptoms and QOL, even when FEV1 does not change much, over a relatively short period of time (eg, 3 years). We wondered if we could find the pathologies responsible for such worsening using chest CT. We also know from a large cohort study (CanCOLD [The Canadian Cohort Obstructive Lung Disease]) that the number of airways visible on chest CT (total airway count or TAC) diminishes significantly across [Global Initiative for Obstructive Lung Disease]-grade severity COPD (Table). But we didn’t know if this meant that this total airway count actually changes substantially over short periods of time. This is important because if the number of airways is diminished over time, airway therapy is unlikely to remain efficacious.
What are the most important findings from your study?
We studied a small group of ex-smokers with and without COPD to measure airway dimensions at baseline and 3 years later. After 3 years, FEV1 was not different in ex-smokers with (P=0.4) and without (P=0.5) COPD. In the absence of FEV1 worsening, TAC diminished in ex-smokers with COPD, and airway walls were thinner in all ex-smokers— those with COPD and those without spirometry evidence of COPD.
How can these findings be incorporated into practice?
We think it is important to follow patients with COPD with chest CT every few years to help provide a framework for how their disease is progressing because FEV1 is relatively insensitive to changes in the small airways where COPD is believed to initiate and from where it worsens.
What would you like future research to be focused on?
We think chest CT measurements of the airways, pulmonary vessels, and parenchyma ought to be included in COPD clinical trials of novel treatments, including biologics. This would help us understand the mechanisms by which some patients respond to therapy, while others don’t.
Is there anything else you would like to mention?
I think it’s important not to overlook smaller studies like this one, which captures the reallife changes patients with COPD and exsmokers undergo over relatively short periods of time.
