Ensuring HLA-matched platelet support requires an ethnic diverse donor population

Factors affecting the efficacy of human leukocyte antigen-selected platelet provision: A large retrospective study in the United Kingdom

BACKGROUND

A large, retrospective study was designed to interrogate current NHS Blood and Transplant (NHSBT) HLA matching strategies for the provision of HLA selected platelets (HLA SP) and to determine whether additional factors such as ABO blood group matching, patient diagnosis, patient and/or donor age, sex, ethnicity, age of platelet unit at transfusion and possibly seasonal variation also play a role in transfusion efficacy.

MATERIALS AND METHODS

Data for 56 640 HLA SP transfusions over a 3-year period were collected. Transfusions with missing data for any factor under consideration were excluded, resulting in a cohort of 13 044 transfusions for analysis. Univariable and multivariable regression models were used to determine if any factors influenced an increase in platelet count of ≥10 × 109/L. A stepwise logistic regression was applied, such that each influential factor was adjusted for effects on other factors included in the study.

RESULTS

HLA match grade was confirmed as a significant factor in transfusion efficacy, with ABO mismatched units 20% less likely to give an adequate platelet increment (≥10 × 109/L). Platelet donor age, gender and ethnicity were not significant. Conversely, patient diagnosis, ethnicity, gender and age showed significant associations with platelet increments. Some seasonal variation in efficacy of platelet transfusion was also demonstrated.

CONCLUSION

This study has demonstrated the efficacy of HLA SP transfusions in refractory patients with a wide range of diagnoses, the importance of HLA match grade, plus the marginal effect of ABO matching. A wide range of donor-related factors was excluded, while a number of patient-related factors were identified, requiring more extensive investigation in ongoing and independent studies, with implications for donor registry, clinical and laboratory practices.

Platelet transfusion refractoriness due to HLA alloimmunization: Evolving paradigms in mechanisms and management

Platelet transfusion refractoriness due to HLA alloimmunization presents a significant medical problem, particularly among multiply transfused patients with hematologic malignancies and those undergoing hematopoietic stem cell transplants. HLA compatible platelet transfusions also impose significant financial burden on these patients. Recently, several novel mechanisms have been described in the development of HLA alloimmunization and platelet transfusion refractoriness. We review the history of platelet transfusions and mechanisms of HLA-sensitization and transfusion refractoriness. We also summarize advances in the diagnosis and treatment of platelet transfusion refractoriness due to HLA alloimmunization.

Sickle cell trait results in a high leukoreduction quality control failure rate for whole blood donations

Background

Prior studies have shown that sickle cell trait (SCT) is the most common reason attributed to leukoreduction (LR) filter failure due to physical blockage. However, current Food and Drug Administration (FDA) guidelines do not require blood collectors to take a specific action to mitigate inadequate LR that may occur among donors with SCT. We sought to determine the scope of inadequate LR among whole blood (WB) donations collected from individuals with SCT and processed under standard manufacturing conditions.

Study Design and Methods

Between 8/2021 and 2/2022, a total of 40 red blood cells units (RBCs) manufactured from WB donations collected from donors historically positive for SCT had residual leukocyte testing performed. All 40 of the units had appeared to successfully complete leukofiltration.

Results

Out of the 40 units tested, 22 failed routine residual leukocyte quality control testing (55% failure rate, 95% confidence interval 40%–70%). Nine out of the 22 failures resulted in more than 100 residual leukocytes per microliter of product.

Conclusion

Even when leukofiltration appears to have been completed successfully, WB units collected from donors with SCT have a high (55% in aggregate) rate of inadequate leukoreduction. Correlating this result with previous studies showing that of up to 50% of WB units collected from donors with SCT fail to pass through the leukoreduction filter, we estimate that only 25% of WB donations collected from individuals with SCT will result in a leukoreduced RBC unit that meets all FDA requirements. Blood centers should encourage individuals with SCT to donate platelets or plasma, rather than WB.

See editorial on page 1683–1687, in this issue

Human Leukocyte Antigen Alloimmunization and Alloimmune Platelet Refractoriness

Despite significant advancements in the production of platelet products, storage, and transfusion, transfusion refractoriness remains a significant clinical problem, affecting up to 14% of hematological patients receiving platelet transfusions. Human leukocyte antigen (HLA) alloimmunization is a major cause of immune platelet refractoriness, and its rate can be significantly reduced by implementation of leukoreduction. Despite promising preclinical results, pathogen reduction does not reduce HLA alloimmunization. Patients with HLA alloimmune refractoriness are usually managed with HLA-selected platelet transfusions. In this review, we describe the pathophysiology of HLA alloimmunization and alloimmune refractoriness, as well as options to prevent and treat these transfusion complications. We discuss the evidence supporting these options and point out the outstanding gaps. Finally, we review the possible future directions for prevention and treatment of alloimmune refractoriness.