Chronic Lung Allograft Dysfunction (CLAD) remains a significant cause of morbidity and mortality following lung transplantation. Bronchiolitis obliterans Syndrome (BOS) is a predominant phenotype of CLAD primarily affecting the small and subsequently the large airways leading eventually to graft failure. In addition, the allograft airways are also involved in other types of CLAD such as Restrictive Allograft Syndrome (RAS). Freedom from BOS at five years post-transplant is only approximately 50 % among lung transplant recipients.
The diagnosis of CLAD is primarily based on pulmonary function testing and radiographic findings on CT scan. Transbronchial biopsies have a low diagnostic yield due to the multifocal nature of CLAD and the frequent lack of bronchioles in the biopsy specimen. Thus, CLAD is often diagnosed after significant disease progression.
We performed endoscopic OCT as a minimally invasive method to identify early CLAD biomarkers. During 65 routine surveillance and event-initiated bronchoscopies of lung transplant recipients at Vancouver General Hospital, OCT imaging was performed prior to acquiring biopsy samples, with multiple 3D volumetric scans taken at locations as close as possible to those biopsied. OCT has the potential to be advantageous over biopsy because multiple airways in the lung can be quickly surveyed. As a first step towards clinical utility we present our methods for quantifying observable biomarkers including luminal size and alveolar density. Ranges of values are established and correlated with airway generation, time since transplant, and infection status.
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