Quantitative CT lung densitometry as an obstructive marker for the diagnosis of bronchiolitis obliterans in children

The purpose of this study is to evaluate the quantitative diagnostic performance of computed tomography (CT) densitometry in pediatric patients with bronchiolitis obliterans (BO). We measured the mean lung density (MLD) and represented the difference of MLD in inspiratory and expiratory phases (MLDD), the ratio of the MLD (E/I MLD), and the relative volume percentage of lung density at 50-Hounsfield unit (HU) interval threshold (E600 to E950). We calculated the sensitivity, specificity, and diagnostic accuracy of the lung density indices for the diagnosis of BO. A total of 81 patients, including 51 patients with BO and 30 controls, were included in this study. In the BO patients, expiratory (EXP) MLD and MLDD were significantly lower, and E/I MLD and expiratory low attenuation areas below the threshold of -850 HU to -950 HU (E850, E900, and E950) were statistically significantly higher than controls. Multivariate logistic regression analysis showed that MLDD (odds ratio [OR] = 0.98, p < .001), E/I MLD (OR = 1.39, p < .001), and E850 to E950 were significant densitometry parameters for BO diagnosis. In a receiver-operating characteristic analysis, E900 (cutoff, 1.4%; AUC = 0.920), E/I MLD (cutoff, 0.87; AUC = 0.887), and MLDD (cutoff, 109 HU; AUC = 0.867) showed high accuracy for the diagnosis of BO. In conclusion, the lung CT densitometry can serve as a quantitative marker providing additional indications of expiratory airflow limitation in pediatric patients with BO.