*Purpose: New oral anticoagulants (NOACs) have replaced warfarin due to their similar efficacy and better safety profile in the general population (GP). The risk of major bleeding with NOAC ranges 3.8-6% in the GP. Although kidney transplant recipients (KTR) frequently require anticoagulation, yet little evidence exists on the use of NOAC in this population. The aim of this study is to assess the safety of NOAC therapy in KTR with non-valvular atrial fibrillation (NV-AF) and venous-thromboembolism (VTE), in comparison to warfarin.

*Methods: This is a retrospective, single-center, two-groups comparative study. All adult KTR receiving NOAC or warfarin for >3 months will be included. Patients were excluded if they were not candidates for NOAC, or had multi-organ transplant. Primary endpoint is the incidence of overall bleeding, both major and clinically-relevant-non-major-bleeding. Secondary endpoints include rate of overall VTE, time-in-therapeutic-rage for warfarin using Rosendaal-method. In addition, the percentage of change in calcineurin inhibitors (CNI) levels upon initiation of anticoagulation will be assessed. Biopsy proven rejections, overall morality, as well as mortality due to bleeding and thrombosis will also be assessed. Statistical analysis: Propensity score matching will be used, furthermore Student-T-test, Mann-Witney-test, and Chi-square will assess the difference of co-variates between patients who are on NOAC compared to warfarin. All reported P were 2-sided and P<0.05 will be considered statistically significant. All statistical analysis will be done using JMP 15.0 from SAS. The calculated sample size is 95 patients in each arm.

*Results: Only preliminary results for the NOAC arm are available. Out of 104 patients screened 63 were included in the NOAC arm. Majority of the patients in the NOAC arm were males (68%), with a mean age of 61 years (±15 SD). Most patients underwent living-transplantation (80%) due to unknown etiology (50%) followed by diabetic nephropathy (25%). Forty-four patients were started on rivaroxaban (70%) while 19 patients were on apixaban (30%). The main indications for starting anticoagulation (AC) were NV-AF (54%) and VTE(46%). Five patients developed overall bleeding (7.9%) with 2 patients developing major bleeding and 3 patients had clinically relevant non-major bleeding. Overall VTE occurred in 2 patients (3%) while mortality due to bleeding and thrombosis was not recorded. There was no statistical significant difference in levels of either CNIs upon initiation of anticoagulation (p >0.05).

*Conclusions: The risk of bleeding while on NOAC in KTR is similar to the GP. Upon data collection completion of the warfarin group we’ll have a better understanding of the risk of bleeding of warfarin compared to NOCA in this population.

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