Background: The purpose of this study was to evaluate the quantitative diagnostic performance of computed tomography (CT) densitometry in pediatric bronchiolitis obliterans (BO) patients. Methods: A retrospective chart review was performed on 109 children under age 18 who underwent 3D chest CT from March 2019 to March 2021. We measured the mean lung density (MLD) and calculated the difference of MLD (MLDD) in expiratory and inspiratory phase, the expiratory to inspiratory ratio of mean lung density (E/I MLD), and the relative volume percentage of lung density at 50 HU intervals (E600 to E950). We calculated the sensitivity, specificity, and diagnostic accuracy of lung density indices for the diagnosis of BO. Results: A total of 81 patients, 51 BO patients and 30 controls, were included in this study (mean age: 12.7 vs 11.4 years). Expiratory (EXP) MLD, MLDD, E/I MLD, and E900 were all statistically significantly worse in the BO group. Multivariate logistic regression analysis showed that MLDD (odds ratio [OR] = 0.98, p < .001), E/I MLD (OR = 1.39, p < .001), and E850 (OR = 1.54, p = 0.003) were significant densitometry parameters for BO diagnosis. In ROC analysis, E900 (cut-off 1.4%; AUC = 0.920), E/I MLD (cut-off 0.87; AUC = 0.887), and MLDD (cut-off 109 HU; AUC = 0.867) showed high accuracy in diagnosis of BO. Conclusion: The quantification of lung density with chest CT complements the diagnosis by providing additional indications of expiratory airflow limitation in pediatric BO patients.

Background: Functional assessment of small airways in young children with bronchiolitis obliterans (BO) is challenging due to their relative inaccessibility and the generally poor lung function test performance of these patients. We analyze the correlation between impulse oscillometry (IOS), spirometry, and plethysmographic parameters in pediatric BO patients. Methods: A total of 89 IOS assessments of pediatric BO patients or children without lung disease were included, and the relationship between pulmonary function tests (PFTs) and diagnostic performance were analyzed. Results: R5, R5-20, X5, and AX were statistically significantly worse in the BO group. In Spearman’s correlation analysis, AX and R5 showed the strongest correlation with conventional PFT parameters, and AX was the variable with the highest relative correlation with FEV1, FEF25-75%, and both measures of plethysmographic resistance. Receiver operating curve analysis highlighted AX and Raw% pred as the most optimal parameters for BO diagnostic performance with areas under curve of 0.811 and 0.827, respectively. Conclusion: The AX and R5 parameters can be useful in identifying the severity of airway obstruction in children with BO, and IOS more generally can accurately detect pathological obliteration of small airways in pediatric BO patients.