Fleming, James N

Background The primary objective of this analysis was to assess the association between non-invasive biomarker results within the first 2-years post-kidney transplant and 10-year All Cause Graft Loss (ACGL). Methods CTOT-08 was linked with the Scientific Registry of Transplant Recipients (SRTR) to assess 10-year ACGL. Cox Regression was used to determine the association between gene expression profile (GEP) and donor-derived cell-free DNA (dd-cfDNA) results and ACGL. A Cox Regression with time-varying covariates was used to test associations with ACGL with simultaneous and repeated biomarker results. Results The final landmarked Cox model included clinical acute rejection (aHR 2.58 (1,30,5.13) for 1 rejection, aHR 3.41 (1.07,10.85) for 2 rejections), diabetes (aHR 1.71 (0.99,2.96)), recipient age (aHR 1.02 (1.00,1.04)), the highest quartile of positive GEP (aHR 2.44 (1.45,4.10)) and the highest quartile of positive dd-cfDNA (aHR 2.91 (1.77,4.78)). In the time-varying model, having both biomarkers positive at the same time carried the greatest association with ACGL (aHR 4.29 (2.10,8.76)). Conclusions In this multicenter, prospective analysis of GEP and dd-cfDNA on patient and graft outcomes, an independent association with long-term ACGL was demonstrated. Further, a time-varying analysis demonstrated that two biomarkers with independent methodologies tested at the same time can provide more information than either one alone.

Key Points Peripheral blood biomarkers may have value in monitoring kidney transplant recipients after treatment of acute rejection. The donor-derived cellfree DNA may be more sensitive to identifying antibody-mediated rejection and gene expression profile may be more sensitive to identifying acute cellular rejection. Background Persistent rejection is an increasingly recognized barrier to long-term kidney allograft survival. A noninvasive method to help identify patients with persistent rejection in need of biopsy would be valuable. Methods This was a post hoc analysis of a multicenter observational study. Patients who had a biopsy-proven acute rejection, had another biopsy within 9 months (270 days), and had a biopsy-paired biomarker sample were included. Results A total of 64 index rejections in 58 patients with repeat biopsies were identified with a median time to repeat biopsy of 100 days. Persistent rejection was present in 61%; 69% of follow-up biopsies were performed in clinically stable patients. Peripheral blood gene expression profile (GEP) demonstrated a sensitivity of 59%, specificity of 76%, positive predictive value (PPV) of 79%, and negative predictive value of 54%. Donor-derived cellfree DNA (dd-cfDNA) demonstrated a sensitivity of 62%, specificity of 86%, PPV of 88%, and negative predictive value of 56%. For repeat biopsies within 90 days of rejection in clinically stable patients (63% of repeat biopsies), both GEP and dd-cfDNA had specificities and PPVs of 100%. GEP was more likely to be positive in T-cell–mediated rejection while dd-cfDNA was more likely to be positive in antibody-mediated rejection. Conclusions Both GEP and dd-cfDNA may have utility in identifying clinically stable patients with persistent rejection in need of biopsy; however, they identify different types of rejections. Clinical Trial registration number: NCT01531257.

AbstractBackgroundThe aim of this study was to correlate peripheral blood gene expression profile (GEP) results during the first post‐transplant year with outcomes after kidney transplantation.MethodsWe conducted a prospective, multicenter observational study of obtaining peripheral blood at five timepoints during the first post‐transplant year to perform a GEP assay. The cohort was stratified based on the pattern of the peripheral blood GEP results: Tx‐all GEP results normal, 1 Not‐TX had one GEP result abnormal and >1 Not‐TX two or more abnormal GEP results. We correlated the GEP results with outcomes after transplantation.ResultsWe enrolled 240 kidney transplant recipients. The cohort was stratified into the three groups: TX n = 117 (47%), 1 Not‐TX n = 59 (25%) and >1 Not‐TX n = 64 (27%). Compared to the TX group, the >1 Not‐TX group had lower eGFR (p < .001) and more chronic changes on 1‐year surveillance biopsy (p = .007). Death censored graft survival showed inferior graft survival in the >1 Not‐TX group (p < .001) but not in the 1 Not‐TX group. All graft losses in the >1 Not‐TX group occurred after 1‐year post‐transplant.ConclusionsWe conclude that a pattern of persistently Not‐TX GEP assay correlates with inferior graft survival.