CT-371: Impact of Donor-Specific Anti-HLA Antibody on Platelet Transfusion Refractoriness in Haplo-Identical Hematopoietic Stem Cell Transplant Patients: A Single-Center Experience

Abstract

Context Outcomes of haplo-identical hematopoietic stem cell transplantation (haploSCT) have recently improved due to better control of allo-reactive reactions related to the major HLA mismatch between the recipient and the donor. Presence of pretransplant donor-specific anti-HLA antibodies (DSA) is associated with higher risk of graft failure. However, little is known regarding the association between the presence of these antibodies and platelet transfusion refractoriness (PTR) post-haploSCT that could predict poor transplant outcomes. Objective The aim of this study is to evaluate the association between DSA status of the recipient and the corrected platelet count increment (CCI) from day 0-100 post-haploSCT as an objective measure of PTR. Design This is a retrospective study that comprises chart review of patients who underwent haplo-SCT between June 2015 and January 2020 at the American University of Beirut medical center in Lebanon. Main outcome measures Pretransplant panel reactive antibodies (PRA) and DSA status at the time of transplant were collected, and the 24-hour CCI was calculated for every platelet donor transfusion. Results We identified 69 patients with a median age of 36 years (range: 16-77). 44 patients (64%) were males and 52 patients (75%) had myelodysplastic syndrome or acute leukemia. Median time from diagnosis to transplant was 13.8 months (range: 2.5-91.7), and 43 patients (62%) were in complete remission at transplant. Of all patients, only 6 patients (8.7%) were DSA+ at time of transplant, 14 (20.3%) were PRA+/DSA-, and the remaining 49 (71%) were PRA-. All 6 patients with DSAs underwent desensitization with a median MFI decrease of 375 (range: -541-1603). One of these 6 did not reach platelet nor leukocyte engraftment. Patients with persistent DSAs had lower mean CCI (9.27, range: 4.58-12.37) compared to those without DSAs (mean CCI: 11.93, range: 1.34-29.71; p=0.017). Statistical significance was maintained upon comparing PRA+DSA+ patients to PRA+DSA- and to PRA- patients with mean CCI of 14.04 (range: 1.39-29.71; p=0.005) and 11.38 (range: 1.34-28.00, p=0.024), respectively. Conclusions Presence of anti-HLA DSAs in haploSCT recipients, even at MFI lower than 1500, was associated with increased PTR. Larger number of patients is needed to evaluate its impact on survival outcomes.