The AQUA registry is a multi-center observational study to assess the clinical management of kidney transplant recipients (KTRs) with use of the QSant test. QSant is a test based on 6 urinary biomarkers including cell-free DNA, that is used for the evaluation and management of acute rejection in renal allograft recipients with clinical suspicion of rejection, as well as subclinical rejection.

The AQUA registry is a multi-center observational study to assess the clinical management of kidney transplant recipients (KTRs) with use of the QSant test. Each participant will be tracked for 24 months. QSant testing will be performed according to the intended use guidelines specified in "LCD - MolDX: Molecular Testing for Solid Organ Allograft Rejection (L38671)", along with all standard of care testing, such as serum creatinine/ estimated glomerular filtration rate (SCr/eGFR) as described in the study schedule. Participants will be compared to a site-specific retrospective cohort of KTRs without QSant testing having received a kidney transplant no more than 5 years prior to study initiation as well as the national cohort derived from UNOS (United Network for Organ Sharing) data.

Inclusion Criteria:

1. Kidney transplant recipient, ≤ 90 days post kidney transplant of any age, solitary or combined multi-organ solid transplants which includes a kidney transplant.
2. Able to understand risks and requirements of participation and provide informed consent
3. Willing and able to comply with the study requirements

Exclusion Criteria:

1. Inability to provide a voided urine sample per collection protocol
2. Urological abnormalities such as augmented bladder, ileo-conduits, mitrofanoff, and vesicostomy.

Kidney transplant recipients of all ages