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.