Taber, David J.

Background and objectives Subclinical acute rejection is associated with poor outcomes in kidney transplant recipients. As an alternative to surveillance biopsies, noninvasive screening has been established with a blood gene expression profile. Donor-derived cellfree DNA (cfDNA) has been used to detect rejection in patients with allograft dysfunction but not tested extensively in stable patients. We hypothesized that we could complement noninvasive diagnostic performance for subclinical rejection by combining a donor-derived cfDNA and a gene expression profile assay. Design, setting, participants, & measurements We performed a post hoc analysis of simultaneous blood gene expression profile and donor-derived cfDNA assays in 428 samples paired with surveillance biopsies from 208 subjects enrolled in an observational clinical trial (Clinical Trials in Organ Transplantation-08). Assay results were analyzed as binary variables, and then, their continuous scores were combined using logistic regression. The performance of each assay alone and in combination was compared. Results For diagnosing subclinical rejection, the gene expression profile demonstrated a negative predictive value of 82%, a positive predictive value of 47%, a balanced accuracy of 64%, and an area under the receiver operating curve of 0.75. The donor-derived cfDNA assay showed similar negative predictive value (84%), positive predictive value (56%), balanced accuracy (68%), and area under the receiver operating curve (0.72). When both assays were negative, negative predictive value increased to 88%. When both assays were positive, positive predictive value increased to 81%. Combining assays using multivariable logistic regression, area under the receiver operating curve was 0.81, significantly higher than the gene expression profile ( P <0.001) or donor-derived cfDNA alone ( P =0.006). Notably, when cases were separated on the basis of rejection type, the gene expression profile was significantly better at detecting cellular rejection (area under the receiver operating curve, 0.80 versus 0.62; P =0.001), whereas the donor-derived cfDNA was significantly better at detecting antibody-mediated rejection (area under the receiver operating curve, 0.84 versus 0.71; P =0.003). Conclusions A combination of blood-based biomarkers can improve detection and provide less invasive monitoring for subclinical rejection. In this study, the gene expression profile detected more cellular rejection, whereas donor-derived cfDNA detected more antibody-mediated rejection.

AbstractThis was a single‐center, randomized controlled trial assessing the impact of a 3‐month (10‐16 weeks) conversion to everolimus with low‐exposure tacrolimus, as compared to remaining on full exposure tacrolimus with mycophenolate (NCT 02096107). Adult kidney transplant recipients with a functioning graft were eligible for participation. Goal troughs in the intervention arm were 2‐5 ng/mL for tacrolimus and 3‐8 ng/mL for everolimus, with tacrolimus maintained at 5‐12 ng/mL in the control arm; 60 were randomized (30 in each arm) and were well matched at baseline; mean age was 51 years and 57% were African‐American. At 12‐months, fibrosis scores (27.8% tacrolimus/mycophenolate vs 22.9% tacrolimus/everolimus, P = .391), acute rejection rates (7% tacrolimus/mycophenolate vs 3% tacrolimus/everolimus, P = .554), and graft function (mean eGFR tacrolimus/mycophenolate 56 ± 15 vs tacrolimus/everolimus 59 ± 14 mL/min/1.73 m2, P = .465) were similar between arms. The everolimus arm had significantly lower rates of CMV infection, severe BK infection, and improved BK viral clearance kinetics, as compared to the MPA arm. In this population, including a significant number of African‐Americans, an immunosuppression regimen of everolimus with low‐exposure tacrolimus provided similar efficacy to tacrolimus and mycophenolate, with significantly lower rates of BK and CMV.