*Purpose: Data is limited on the association of Mycophenolic Acid (MPA) concentration on protocol kidney transplant biopsies. Our aim is to compare clinical outcomes and subclinical histological scores in kidney transplant recipients on protocol biopsies at 12 months post-transplant based on their MPA concentrations. Our hypothesis is that MPA levels < 2 mcg/mL are associated with higher rates of inflammation on protocol kidney biopsies.

*Methods: All kidney transplant recipients from January 2013 to December 2014 who had MPA levels at 12 months after transplant were included in the study. We collected pathology data from biopsies, MPA levels, tacrolimus levels, serum creatinine, and BK serum PCR. The primary outcome was histologic findings of inflammation on protocol biopsies at 12 months. The cohort was stratified by the 12 month MPA level (< 2 vs > 2). Induction therapy was Basiliximab, Alemtuzamab, or Thymoglobulin based on immunologic risk. Any continuous variable in the table is shown as the mean (standard deviation).

*Results: A total of 462 patients were included in the analysis. Baseline demographics are in Table 1. Patients with MPA level < 2 mcg/mL at 12 months were more likely to have BK infection when compared to those with higher levels (28% vs. 18%, p=0.03) however there was no difference in rejection, eGFR, or steroid maintenance therapy. Tacrolimus levels were similar at most time points during the first year except at 12 months where it was lower in the MPA < 2 group (5.8 vs 6.6, p=0.004).

MPA levels < 2 mcg/mL at 12 months were associated with higher rates of t-scores > 0 (19.2% vs. 8%, p = 0.01) and i scores > 0 (20.6% vs 8%, p = 0.02) in patients without BK infection. Long term graft and patient survival was lower in patients with MPA levels < 2 mcg/mL at 12 months, a finding that persisted when excluding those with BK infection (Figure).

*Conclusions: Low MPA levels (< 2 mcg/mL) at 1 year correlate with subclinical inflammation and increased risk of allograft loss or patient death, independent of BK infection. Immunosuppression modification should be considered in individuals with low MPA levels.

« Back to 2020 American Transplant Congress