*Purpose: Surveillance allograft biopsies (SVAB) are used by many centers to identify subclinical immunologic injury. SVAB entails bleeding risks. Non-invasive modalities such as donor-derived cell-free DNA (dd-cf DNA) and donor specific antibodies (DSA) are used as indicators of kidney injury/immunologic activity. This study compares the results of SVAB, dd-cf DNA assay, and DSA.

*Methods: Retrospective, single center chart review of 73 consecutive patients undergoing SVAB between 2/2019-11/2019 that had associated dd-cf DNA (Allosure®) and DSA results. SVAB was positive if it showed cellular (greater than borderline changes) and/or antibody mediated rejection. dd-cf DNA was positive at >1% and DSA was positive at 1500 MFI. A single SVAB is performed 6-12 months after transplantation at our center. All patients received tacrolimus, mycophenolate, and steroids.

*Results:

Using dd-cf DNA alone sensitivity was 40%, specificity was 94%, positive predictive value (PPV) 33%, and a negative predictive value (NPV) 96%. When either the dd-cf DNA or DSA were positive, sensitivity of 100%, specificity of 94%, PPV of 33%, and NPV of 100%.

*Conclusions: The use of dd-cf DNA is a feasable screen for allograft rejection with a high NPV of 96% and if DSA was negative, the NPV increased to 100%. In this group, 55 SVAB and associated risks could have been avoided. Furthermore, SVAB can be an inconvenience to patients such as those traveling long distances to their center as blood for these tests can be done locally. Patients on anticoagulation can be safely screened as well. This, using dd-cf DNA along with DSA may be an alternative to SVAB as a screen for allograft rejection after transplantation. More data will be required to confirm our findings.

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