Lung transplant is a viable treatment strategy for many with end-stage lung diseases. Despite advances in both the surgical and medical management, lung transplant recipients experience episodes of allograft insult and injury that lead to dysfunction and ultimately contribute to graft failure. The primary noninvasive tool for monitoring the lung allograft, pulmonary function testing, is neither sensitive nor specific for lung allograft injury which makes the management of lung transplant recipients particularly challenging. A decline in pulmonary function tests prompts invasive procedures such as bronchoscopy with transbronchial lung biopsy to diagnose the cause of allograft injury, although this, too, is not 100% sensitive, and oftentimes patients are treated empirically for rejection when no other etiology for lung function decline is identified. Empiric treatment prompted by extrapulmonary drivers of decline in lung function may result in inappropriate exposure to risks of augmented immunosuppression. The purpose of this study is to determine to what extent monitoring of donor-derived cell free DNA in lung transplant recipients can be used as a marker of lung injury and stability.

Inclusion Criteria:

• ≥ 18 years old
• Actively listed or have recently had a double lung transplant
• Participant is willing and able to provide informed consent

Exclusion Criteria:

• Prior organ transplantation
• Transplantation performed in the setting of hospitalization for acute illness or decompensation
• Unable or unwilling to consent for enrolment
• Single lung transplant recipient
• Consideration for multi-organ transplantation
• Pregnant women

Adult patients with end stage lung disease who are placed on the lung transplant waitlist for consideration of a bilateral transplant at the University of Colorado lung transplant program will be recruited for participation in the study.