The ProActive registry is a longitudinal, multi-center study with a prospective arm observing clinical care for patients receiving physician ordered Prospera, an allograft rejection test, and a historical control arm collecting data on cases at the same sites whose kidney allograft rejection status was managed with Serum Creatinine SCr/estimated Glomerular Filtration Rate eGFR. This registry will compare patient management and outcomes in patients who receive Prospera (Prospera arm) to the outcomes of the historical control group (control arm) to determine Prospera's clinical utility. High-risk subjects defined as having a biopsy-demonstrated rejection event or at least one pre-existing Donor Specific Antibody DSA with total Mean Fluorescent Intensity MFI>3000 or a calculated Panel Reactive Antibodies cPRA>70% will be followed for an additional period up to 24 months in both the Prospera arm and historical control arm.

The primary objective is to differentiate the clinical utility of Prospera testing from the use of creatinine testing as measured by the proportion of positive biopsies in post renal allograft patients.

Secondary objectives include:

• To observe the performance of the Prospera assay in detecting AR (repeated validation)
• To evaluate whether Prospera can detect AR earlier and more often than SCr
• To determine whether use of Prospera will significant decrease the rate of overall number of biopsies when compared to the rate of biopsies in the control arm

Inclusion Criteria Prospera Arm:

1. 18 years of age or older
2. Renal allograft (kidney transplant) up to 2 years prior to signing informed consent. Newly transplanted patients to receive Prospera testing within 60 days of transplant
3. A genetically different donor (not an identical twin)
4. Selected by a healthcare provider to receive Prospera dd-cfDNA test according to the regular interval testing schedule as part of their practical care
5. Able to read, understand and provide written informed consent
6. Willing and able to comply with the study visit schedule and study requirements

Exclusion Criteria Prospera Arm:

1. Pregnant
2. Routine ongoing testing with another dd-cfDNA or RNA biomarker test after enrollment into the ProActive study. Receipt of another dd-cfDNA test within 30 days of a patient being enrolled in the study.
3. History of another organ transplant (i.e. aside from renal allograph)
4. A serious medical condition that may adversely affect ability to participate in the study (e.g, dementia, current diagnosis of cancer)
5. Previously enrolled in the ProActive Registry, with the exception of a graft failure and a new renal allograft

Inclusion Criteria Control Arm:

1. 18 years of age or older at the time of transplant
2. Had a renal allograft
3. Had a genetically different donor
4. Had a minimum of three evaluations per year during the three years since the renal allograft or until allograft failure

Exclusion Criteria Control Arm:

1. Female patients who were pregnant at any time during the 3-year historical control data collection period
2. Had a transplanted organ other than kidney
3. Received results from a dd-cfDNA test designed to assess renal allograft rejection during the historical control data collection period

Approximately 5,000 adult renal allograft participants will be enrolled in this study, and data will be collected from a de-identified cohort of approximately 500 historical control patients who had a renal allograft.