Practice Patterns and Clinical Outcomes of Platelet Alloimmunization in a Comprehensive Cancer Center
Authors: Goswamy Rohit V , Tannenbaum Daniel J , Aung Fleur M. , Rojas Hernandez Cristhiam Mauricio 
Published: November 2019

Introduction
Platelet transfusion refractoriness (PTR) secondary to human leukocyte antigen (HLA) alloimmunization is a challenge in the treatment of hematology oncology patients and increases the risk of morbidity and mortality from bleeding events. Guidelines for treating PTR have not been clearly described in literature and the use of TPO mimetics or antifibrinolytics in routine clinical practice in the setting of PTR has not been well studied.
Aim
In this study, we aimed to describe the practice patterns for the management of PTR secondary to HLA alloimmunization, its supportive care interventions and to assess the mortality, thrombosis and bleeding related clinical outcomes at 30 days from the diagnosis of PTR and HLA alloimmunization.
Methods
A retrospective review was conducted of all PTR in adult hematology oncology patients at MD Anderson Cancer Center between May 2017 and April 2019. PTR was defined as post-transfusion platelet count increment < 10,000 per microliter in at least two consecutive occasions and within 24 hours after platelet transfusion. HLA typing, HLA antibody and platelet transfusion data were obtained from the Blood Bank Electronic records. Patient demographics and clinical data were obtained from the patients electronic medical records. The study was approved by the Institutional Review Board.
Results
A total of 51 cases of PTR secondary to HLA alloimmunization were analyzed. The majority of patients (98%) had a diagnosis of hematological malignancy of which 88.2% were undergoing active chemotherapy. Clinically relevant bleeding was observed in 33.3% while hemorrhagic shock was diagnosed in 7%. The rate of bleeding related-mortality was estimated at 7.8% (Table 1a). There was great heterogeneity in the management of bleeding risk and events. The use of antifibrinolytics and plasma products (including intravenous immunoglobulin) was more common in cases with major versus non-major bleeding (Table 1b). Grade A or B1U HLA matched products were available in less than half of cases.
Conclusions
Our study depicts several important observations related to clinical practice and supportive care during HLA platelet alloimmunization and PTR.
1. There is heterogeneity in the management of the bleeding risk and bleeding events during platelet refractoriness.
2. Antifibrinolytics are more commonly used in the patients who suffered severe bleeding.
3. Grade A and BU HLA-matched platelets are not always readily available.
4. The HLA typing and HLA antibody screen/identification testing are not always performed prior to PTR.
5. There is a significant morbidity impact on clinical outcomes due to PTR and its bleeding related complications.
Limitations of our retrospective study include the underestimation of actual bleeding outcomes and clinical reasons for the selection of supportive measures (i.e. concern for thrombosis, renal failure). Prospective randomized control trials may be able to determine the safety and efficacy of antifibrinolytics and other supportive measures in the management of PTR.

Disclosures
No relevant conflicts of interest to declare.