Optimal timing and dosing of platelet transfusions

Background Over the past 20 years there have been more than 20 randomized controlled trials (RCTs) that have investigated various aspects of platelet transfusion therapy in haematology/oncology patients. These studies have focused on the best platelet product, the importance of ABO compatibility, pathogen inactivation of platelets, platelet triggers and the optimal platelet dose. Aims This article summarizes current evidence to support the timing and dosing of platelet transfusions and to explore some ideas of where clinical research in this area may be heading. Materials and Methods The articles reviewed in this presentation were identified through a search of PubMed using the term, platelet transfusion and setting limits to identify clinical studies, human studies and manuscripts in English. Results and Discussion Three RCTs have informed practices around platelet transfusion trigger with the largest study by Rebulla et al. , being the primary study that has changed practices worldwide, with a move towards a lower prophylactic platelet transfusion trigger of 10 × 10 9 /l. Two groups (Germany and Oxford, UK) are currently investigating whether we can push the boundaries of prophylactic platelet transfusions even further by eliminating this form of therapy. Preliminary results from these studies have been published but we will await the final results to determine whether this research will indeed change practice. Over the past year there has also been two major studies (one by the BEST Collaborative, and the second by the US Transfusion Medicine/Hemostasis Network), that provide new information to guide platelet dosing. The Study by the BEST Collaborative (SToP) compared low dose platelets to standard dose platelets with WHO bleeding greater than or equal to Grade 2 as the primary outcome. The US study (PLADO) compared three doses (low, medium and high) and measured the same outcome (WHO bleeding ≥ Grade 2). Conclusions Although all of these studies further our knowledge to prescribe platelet transfusions, they also raise some interesting questions about the clinical relevance of the outcomes that we are currently using for these studies. The trend over the past decade has been to use bleeding as the primary outcome; however, bleeding is a complex composite outcome (Grades 2, 3 and 4) comprised of some surrogate components (Grades 2 and 3). It is also an outcome that may be difficult to measure and grade in a consistent and reliable manner. The clinical relevance of this outcome is also complex and may vary depending on the perspective from which it is viewed.