Loss of FEV1 in cystic fibrosis: correlation with HRCT features.

The purpose of this study was to determine which high-resolution computed tomography (HRCT) features in patients with cystic fibrosis are most strongly associated with functional impairment as expressed by forced expiratory volume in one second (FEV1). Forty-seven patients with cystic fibrosis underwent chest HRCT and had pulmonary function tests. The HRCT examinations were evaluated for 11 features scored using a modification of Bhalla system and FEV1 was recorded as percentage of the predicted value. Univariate and multivariate correlations between HRCT scores and FEV1 were performed. The most common HRCT feature was bronchiectasis (98%) followed by atelectasis-consolidation (81%), bronchial wall thickening (77%), tree-in-bud sign (74%), mucous plugging (72%) and mosaic perfusion pattern (47%). On univariate analysis the following features correlated strongly with FEV1: bronchial wall thickening ( p<0.0000001), tree-in-bud sign ( p<0.0000001), mucous plugging ( p<0.0000001), atelectasis-consolidation (p<0.0000001), thickening of interlobular septa ( p<0.0002), severity ( p<0.0002) and extent of bronchiectasis ( p<0.0002). On multivariate analysis bronchial wall thickening and atelectasis-consolidation were the strongest independent determinants of the FEV1. We found a regression equation between FEV1 and the two HRCT features: FEV1=constant variable+a multiplied by bronchial wall thickening+b multiplied by atelectasis-consolidation (a and b=regression coefficients, R(2)=0.48). The major morphological determinants of functional abnormality in cystic fibrosis, as expressed by the loss of FEV1, are bronchial wall thickening and atelectasis-consolidation.