P105 Single-center experience in routine post-transplant antibody testing of risk-stratified kidney transplant recipients

Abstract

Aim Preformed (pf) and de novo(dn) donor-specific antibodies (DSA) are associated with antibody mediated rejection (AMR). We previously showed that ∼6% of low-risk renal transplant (tx) patients developed dn DSA at 1 year (y) post-tx (ASHI, 2016). This study extends our findings over 2y post-tx for low-risk, as well as for intermediate- and high-risk groups. Methods Our Tx Center instituted routine post-tx antibody (Ab) testing by bead array in 2014. Frequency of post-tx monitoring was based on perceived risk for AMR due to DSA in a pre-tx sample: low (no DSA ever) at 1y; intermediate (historic pfDSA, flow crossmatch [FCXM] negative) at 1, 3, 6, and 12 months (m); high (current pfDSA, FCXM negative) at 2 weeks, 1, 3, 6, and 12 m. All groups with functioning grafts were monitored annually thereafter. Additional testing was performed due to planned or unplanned change in immunosuppression (IS) regimen. Results From May 2014-June 2015, 73 patients received a kidney only tx with HLA immunologic risk as follows: 61 low (84%), 2 intermediate (3%), and 10 high (14%). Of low-risk patients, 54 were tested at 1y post-tx while 30/54 low-risk patients were tested at 2y post-tx (at time of analysis). In addition to 4 previously described patients with dnDSA at 1y post-tx, 3 patients developed dnDSA just beyond the 1y post-tx: 2 were tested due to IS change (decreased due to BK virus infection, another, to non-adherence) while 1 was due to graft dysfunction. On biopsy (bx), both low-risk patients tested for IS change had chronic changes while the patient with acute dysfunction had chronic Ab mediated rejection. Of 2 intermediate-risk patients, 1 developed dnDSA by 1 m post-tx with chronic changes on bx. Finally, 1/10 high-risk patients had increased strength of pfDSA and suffered acute AMR while another developed dnDSA (no increase in pfDSA) following IS change. The patients with dnDSA are being monitored more closely. Conclusions In patients with routine post-tx Ab testing (n = 66), dnDSA was detected in 15% (7 low- 1 intermediate- and 2 high-risk); 1 high-risk patient developed increasing pfDSA. Strikingly, changes in IS (decrease due to infection or non-adherence) led to development of dnDSA. This suggests that routine post-tx DSA testing may be help identify evolving alloresponses and guide management but further analysis is needed.