Background/Case Studies: Human leukocyte antigen (HLA) alloimmunization is one of the most common etiologies of platelet (plt) refractoriness. Alloimmunization develops after exposure to non self HLAs through pregnancy, transfusion, or solid organ/mismatched hematopoietic stem cell transplant (HSCT). Requesting an HLA match/compatible plt usually causes delays in patient care and increase the cost of transfusion from blood bank perspective. In this study we evaluate the need for HLA matched/compatible plt in our post HSCT patients.
Study
Design/Methods: In this retrospective study from January 2021- April 2025, we evaluated all our HLA plt orders in the blood bank. Data extracted from electronic medical records included patient demographics, underlying disease, history of pregnancy, HLA lab result (luminex single antigen bead assay), calculated panel reactive antibody (CPRA), and Red Blood Cell (RBC) alloantibody. Any inpatient plt order for a non-bleeding, non-febrile patient with a plt >10,000 µL, or any second platelet order within 24 hours, is audited and triaged within our institution.
Results/Findings: A Total number of 22,827 plt units have been transfused since January 2021 in our institute. Out of those, 189 were HLA-matched/compatible units for 33 patients (26 female, 20 Caucasian, with an average age of 58.9 years). Among the 33 patients, 20 (15 female, 12 Caucasian, with an average age of 59 years) of them were post HSCT with a plt transfusion threshold of less than 10,000 µL (Table.1). A total of 393 HSCT were done in our institute.
Out of 20 post HSCT patients, 12 (6 with Acute Myeloid Leukemia (AML) and 3 with Myelodysplastic Syndromes (MDS)) had a CPRA >80%, presenting challenges/delay to our blood supplier in providing HLA- matched/compatible plts. The majority of these HLA-alloimmunized post HSCTs with CPRA >80% were female (n=10) with a history of pregnancy (n=9) and were Caucasian (n=9).
Conclusions: Plt HLA alloimmunization is common in AML patients, which can cause immune-mediated plt refractoriness. Therefore, decreasing the number of blood product transfusions in by adjusting the transfusion threshold should be considered, especially for non-bleeding, non-febrile Caucasian female AML patients.
