Abstract
ObjectivesTo determine the correlation between CT measurements of emphysema or peripheral airways and airflow obstruction in chronic obstructive pulmonary disease (COPD).MethodsPubMed, Embase and Web of Knowledge were searched from 1976 to 2011. Two reviewers independently screened 1,763 citations to identify articles that correlated CT measurements to airflow obstruction parameters of the pulmonary function test in COPD patients, rated study quality and extracted information. Three CT measurements were accessed: lung attenuation area percentage < -950 Hounsfield units, mean lung density and airway wall area percentage. Two airflow obstruction parameters were accessed: forced expiratory volume in the first second as percentage from predicted (FEV1 %pred) and FEV1 divided by the forced volume vital capacity.ResultsSeventy-nine articles (9,559 participants) were included in the systematic review, demonstrating different methodologies, measurements and CT airflow obstruction correlations. There were 15 high-quality articles (2,095 participants) in the meta-analysis. The absolute pooled correlation coefficients ranged from 0.48 (95 % CI, 0.40 to 0.54) to 0.65 (0.58 to 0.71) for inspiratory CT and 0.64 (0.53 to 0.72) to 0.73 (0.63 to 0.80) for expiratory CT.ConclusionsCT measurements of emphysema or peripheral airways are significantly related to airflow obstruction in COPD patients. CT provides a morphological method to investigate airway obstruction in COPD.Key Points • Computed tomography is widely performed in patients with chronic obstructive pulmonary disease (COPD) • CT provides quantitative morphological methods to investigate airflow obstruction in COPD • CT measurements correlate significantly with the degree of airflow obstruction in COPD • Expiratory CT measurements correlate more strongly with airflow obstruction than inspiratory CT • Low-dose CT decreases the radiation dose for diagnosis and quantitative emphysema evaluation Electronic supplementary materialThe online version of this article (doi:10.1007/s00330-012-2480-8) contains supplementary material, which is available to authorized users.
Highlights
Chronic obstructive pulmonary disease (COPD) is characterised by airflow limitation that is not fully reversible [1]
Airflow obstruction parameters in the pulmonary function test (PFT) by spirometry is essential in chronic obstructive pulmonary disease (COPD) diagnosis, these parameters fail to quantify the proportionate impact of emphysema and small airways disease individually
Articles were included in the systematic review if they: (1) analysed the association between computed tomography (CT) quantitative emphysema or airway measurements and PFT; (2) investigated human beings; (3) included participants diagnosed with stable adult COPD, according to the Global initiative for chronic Obstructive Lung Disease (GOLD) [1] or the American Thoracic Society (ATS) or the European Respiratory Society (ERS), or clearly defined similar criteria; (4) included participants who had clearly described PFT, according to the guidelines of the ATS, ERS or similar methods
Summary
Chronic obstructive pulmonary disease (COPD) is characterised by airflow limitation that is not fully reversible [1]. The pathogenesis of airflow limitation in COPD is mainly related to emphysema and small airway remodelling [2]. Airflow obstruction parameters in the pulmonary function test (PFT) by spirometry is essential in COPD diagnosis, these parameters fail to quantify the proportionate impact of emphysema and small airways disease individually. Quantification of airway remodelling by CT is challenging because of its spatial resolution. Airway wall quantification started over a decade ago, mainly for large airways [3], but investigators have measured the peripheral airways down to 0.5-mm-lumen diameter [10] and 2.8 mm outer diameter [11]. Measurement of narrowing of CT-detectable airways may estimate the degree of small airways disease [10]
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