Probe-based confocal laser endomicroscopy (pCLE) in chronic rejection after lung transplantation: A pilot study

Background . Bronchiolitis obliterans syndrome (BOS) remains a significant burden after lung transplantation (LTx). Histopathological diagnosis of BOS on transbronchial biopsies obtained during surveillance bronchoscopy is challenging, making it a clinical diagnosis based upon the absence of other causes of lung functional decline. pCLE is a novel imaging technique enabling real-time & in vivo visualization of the pulmonary acinus. Methods . In this prospective, observational study, 24 lung transplant recipients were subjected to pCLE on the occasion of surveillance bronchoscopies during the first two years following LTx. Morphometrical data were analyzed for patients with and without BOS development over time. Results . All patients developing BOS (n= 7) showed a mean decrease in FEV1 of 25% with a significant correlation between FEV1 decline and the change in the area of the alveolar openings at the level of the alveolar duct (AAD) (Pearson r=0.61; p=0.02). Morphometrical analysis showed a mean decrease of 26% in AAD and a mean increase of 9% in the thickness of the elastin framework surrounding the alveolar duct openings (TEF). In all patients without BOS (n=17), we noted a mean increase in FEV1 of 8% over time (p<0.0001). Morphometrical analysis showed a mean increase of 1% in AAD (p=0.003) and a mean decrease of 6% in TEF (p=0.08). Conclusion . Morphometrical analysis after pCLE in patients developing BOS, showed a decrease in AAD and a trend for an increase in TEF when compared to other patients. Whether these findings could be specific for BOS and if they represent an ultra-structural substrate for FEV1 decline, should be prospectively confirmed in a larger cohort.