*Purpose: Post-transplant care is multifaceted with protocols to provide oversight and maintain the standard of care. While institutional protocols for post-transplant HLA antibody surveillance after a positive virtual crossmatch (VXM) are often implemented, the impact on outcomes and survival is unclear. Our program implemented a protocol for antibody mediated rejection (AMR) surveillance for HLA donor specific antibodies (DSA) on post-transplant day 3 and 7 for patients with positive retrospective flow crossmatch (FXM), positive virtual crossmatch (VXM), DSAs present on VXM within 3 months, or DSAs newly detected on the serum sample tested for FXM.

*Methods: Patients who received cardiac transplant between January 2018 and September 2020 in our center were retrospectively reviewed. Data was compiled to evaluate our protocol for DSA surveillance and survival at one-year post transplant. Multi-organ and re-transplant patients were excluded from the study.

*Results: Of 143 eligible patients, 38 (27%) were positive for DSA at VXM. Of the 105 patients with negative VXM, 9 tested positive for DSA on sample used for FXM. Of those negative for DSAs on either crossmatch, only 8% developed DSAs by days 3 and 15% by day 7. Of those with DSAs on either crossmatch, 38% remained positive on days 3 and 7. Out of these patients, one was positive at day 3 with MFI increasing on day 7. Treatment for AMR was initiated on day 8. Only 18% of initially positive patients remained positive at 1 year. 21% were treated for rejection despite only 3% showing biopsy evidence of rejection. At 1 year, 91% of positive patients were alive.

*Conclusions: Our findings suggest that patients positive for DSAs do not have inferior short-term outcomes compared to those negative for DSAs when early and serial HLA antibody testing was performed. This protocol allows early detection of DSAs and prompt management of potential rejection which could improve overall survival.

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