Additional Relevant Details The Circulating Donor-Derived Cell-Free DNA in blood for diagnosing Acute Rejection in Kidney Transplant Recipients (DART) study is a prospective, multicenter, observational study of kidney transplant recipients. Blood specimens and information on allograft status are serially collected at planned post-transplant surveillance visits and also when allograft rejection is suspected or treated. The study is part of the clinical validation plan for AlloSure, a proprietary diagnostic test that measures the fraction of donor-derived cell-free DNA (dd-cfDNA) in the blood of transplant patients as a new tool for the non-invasive detection of clinical or sub-clinical rejection.