Cf-DNA Assay During Treatment of Acute Rejection-Pilot Study

Significance of Research Question/Purpose:

A kidney transplant biopsy is the gold standard for making a diagnosis at the time of graft dysfunction. However, there are risks associated with a transplant biopsy (e.g., hematuria, clots within the collecting system, bleeding, hematoma within the kidney, urine leak, and rarely AKI and/or graft loss). Recently, a blood test has been developed which distinguishes donor and recipient circulating cf-DNA. Using this methodology, circulating cf-DNA is amplified, then using a panel of markers, 2 DNA peaks can be observed - a high peak for the recipient DNA and a very low peak for the donor (importantly, this is not genetic testing; only high and low peaks are identified). When cf-DNA is measured at the time of a kidney biopsy for graft dysfunction, an elevated donor cf-DNA level - compared to that seen in a cohort without inflammation - can be seen in recipients with an acute rejection (AR) episode. Data, to date, suggests that if >1% of cf-DNA is donor derived, there is likely graft inflammation.

Currently, there are ongoing studies to determine if sequential measurement of cf-DNA in the same recipient will show elevated donor cf-DNA levels earlier than a serum creatinine rise, thus potentially allowing earlier detection and treatment of AR episodes.

Serum creatinine level is used as a marker for successful treatment of an acute rejection episode. However, creatinine level is an insensitive marker of response to treatment of both cellular and antibody mediated rejection. Studies in which biopsies are done at the end of "presumed" successful rejection treatment show that some patients whose creatinine level returned to baseline have ongoing inflammation. Unless additional anti-rejection treatment is given, this incomplete treatment leads to increased risk for donor-specific antibody formation and graft failure.

As a consequence, the investigators (the U of MN Kidney Transplant Program) are now doing routine "exit" biopsies for patients treated for acute rejection episodes and whose serum creatinine level returns to baseline. The investigators have always done biopsies in patients whose creatinine level did not return to baseline. The "exit" biopsy is done at ~6 weeks after completion of rejection treatment. If the exit biopsy shows ongoing inflammation, additional rejection treatment is considered.