The purpose of the study is to continue to follow subjects who were enrolled in the CTOT-20 CLAD Phenotypes study. Subjects will provide clinical data and complete quality of life questionnaires that will be used to determine the clinical factors associated with the development of Chronic Lung Allograft Dysfunction (CLAD) after lung transplant.

There are no mandated study visits, rather the study will be conducted using real world data collected as part of usual clinical care according to the standard of care transplant protocols at each site. Specimens and study data will be collected during standard of care visits and study coordinators will review medical records and extract available clinical data every 6 months. Study coordinators will collect Pulmonary Function Test data that will be transferred to the Data Coordinating Center as in CTOT-20. Subjects will be asked to complete quality of life questionnaires on an annual basis.

The majority of times, blood samples will be collected during clinical care routine venipuncture based on clinic visit scheduling. In the rare circumstances in which research blood is missed during a standard of care venipuncture or one is not scheduled, a participant may be asked to undergo venipuncture for study purposes.

Standard of care (SOC) bronchoscopies with collection of Bronchoalveolar Lavage (BAL) lung fluid will be performed at each center according to clinical management protocols. During SOC bronchoscopies, research participants will undergo additional fluid instillation for research BAL sampling as in CTOT-20.

Inclusion Criteria:

• Current CTOT-20 participants

Exclusion Criteria:

• Non-CTOT-20 participants
• Withdrawn CTOT-20 participants

This study will include participants previously enrolled in the CTOT-20 study who are alive and remain active in the study (i.e. not previously withdrawn). The CTOT-20 cohort consists of adults who received their first lung transplant at one of the five participating centers (Duke University Medical Center, University of California Los Angeles Medical Center, Cleveland Clinic Foundation, Johns Hopkins University, Toronto General Hospital). Multi-organ recipients as well as prior recipients of any solid organ or bone marrow transplant were excluded. Recipients with HIV infection were excluded as were those participating in an investigational drug trial at the time of enrollment. At the time of this protocol writing, there are 625 out of 803 CTOT-20 participants alive and active in follow-up, who are eligible to participate.