Early diagnosis of bronchiolitis obliterans syndrome diagnosis after lung transplantation using functional respiratory imaging (FRI)

Background: Chronic lung allograft dysfunction after lung transplantation (LTx) manifests as a sustained decline in FEV1, which heralds the onset of bronchiolitis obliterans syndrome (BOS). Identifying regional disease in the lungs could lead to earlier diagnosis of BOS and potentially improved outcomes. We have shown that Functional Respiratory Imaging (FRI) can assess post LTx changes in lung structure and function that correlate with onset of BOS. Methods: Paired inspiratory-expiratory CT scans of 29 LTx patients (22 BOS and 7 non BOS) were analyzed. All patients experienced a reduction in FEV1>10% compared to baseline (BOS 0-p). Differences between the two groups were analyzed for lung function and FRI parameters. Results: A significant increase in transplanted lung volume derived from the expiratory HRCT scans was observed in the subjects diagnosed with BOS compared to the non-BOS patients. On the other hand, the FEV1 change between the two groups was not statistically different. Conclusion: FRI could differentiate early BOS from non-BOS in LTx patients, whereas FEV1 could not. An increase in FRC volume of the transplanted lung in the BOS group is likely a consequence of progressive airflow obstruction which characterizes this disease. These results suggest that FRI can be a potential biomarker to assist in early BOS diagnosis, and may be more sensitive than FEV1.