Post-lung transplantation bronchiolitis obliterans syndrome: Usefulness ofexpiratory thin-section CT for diagnosis

PURPOSE: To assess the usefulness of thin-section expiratory computed tomog raphy (CT), as compared with that of thin-section inspiratory CT, in detect ing airway obstruction and air trapping in pediatric lung transplant recipi ents with bronchiolitis obliterans syndrome (BOS). MATERIALS AND METHODS: Thin-section CT scans were obtained at full inspirat ion and end expiration in 21 pediatric lung transplant recipients with prov ed BOS and in 41 transplant recipients with normal airways. True diagnosis was based on pulmonary function test results. Inspiration CT scans were sco red for extent of decreased attenuation of the lung parenchyma; expiration CT scans were scored for extent of air trapping. RESULTS: The sensitivity of inspiratory CT for enabling diagnosis of BOS wa s 71 %; the specificity, 78%; the positive predictive value, 62%; and the n egative predictive value, 84%. The sensitivity of expiratory CT for enablin g diagnosis of BOS was 100%; the specificity, 71%; the positive predictive value, 64%; and the negative predictive value, 100%. Expiratory CT scores c orrelated more strongly (p = 0.75, P < .01) with pulmonary function test-ba sed scores than did inspiratory CT scores (rho = 0.48, P < .01). Nominal lo gistic regression analysis revealed that expiratory CT was a more powerful predictor of true diagnosis (P < .01) than was inspiratory CT (P = .10). CONCLUSION: Expiratory CT is sensitive for depicting BOS-related airway abn ormalities and may be more useful than inspiratory CT for diagnosis of smal l airway obstruction.