ORIGINAL RESEARCH Factors related to the outcome of prophylactic platelet transfusions in patients with hematologic malignancies: an observational study Audrey Seigeot, 1 Maxime Desmarets, 2 Anne Rumpler, 3 Franck Leroux, 2 Eric Deconinck, 3,4 Elisabeth Monnet, 2,5 and Laurent Bardiaux 4,6 BACKGROUND: A better knowledge of the connections between platelet concentrate (PC) characteristics and transfusion outcomes in day-to-day practice would help improve the selection process of the most appropriate PC. STUDY DESIGN AND METHODS: In this study of prophylactic platelet transfusions in patients with hematologic malignancies between 2002 and 2012, outcome criteria were corrected count increments (CCIs) and platelet transfusion intervals (TIs, in days). Studied characteristics were ABO matching status, platelet source, dose, storage duration, irradiation, washing, and transfusion sequence number (TSN). The analysis consisted of multivariable linear mixed-effects models with adjustments for patient diagnosis, sex, and type of treatment. RESULTS: Overall, 869 patients and 6662 platelet transfusions were analyzed. For each day after the second day of storage, the CCI and TI decreased by 0.88 and 0.06 day, respectively. Compared to ABO-identical, transfusion with major ABO-incompatible PCs decreased the CCI and TI by 0.79 and 0.21 day, respectively. Platelet washing reduced the CCI and TI by 2.28 and 0.24 day, respectively. There was no significant association between platelet source or irradiation and CCI or TI. TI increased as the platelet dose per kg increased. Both CCI and TI decreased as the TSN increased. CONCLUSION: Transfusion outcomes were significantly related to several PC-related factors. Associations for ABO matching status and storage duration were stronger than previously reported. Taking into account such factors when selecting a PC for transfusion could be beneficial to the recipient. P latelet transfusions are used to prevent and treat bleeding in thrombocytopenic patients with bone marrow failure secondary to disease or che- motherapy. It is common practice throughout the world to use platelet transfusions in thrombocytope- nic patients without patient bleeding. The French National Authority for Health (Haute Autorit e de Sant e, HAS) recommends prophylactic transfu- sions for any severe thrombocytopenia after chemotherapy with or without hematopoietic stem cell reinjection. 1 The current recommended dose is 0.5 to 0.7 3 10 11 platelets per 10 kg of weight, with a prescription threshold of 10 3 10 9 /L in the absence of symptoms; 20 310 9 /L in case of fever, infection, arterial hypertension, Grade 2 mucositis, and ABBREVIATIONS: AP(s) 5 apheresis platelet(s); HAS 5 Haute Autorit e de Sant e; PC(s) 5 platelet concentrate(s); TI(s) 5 transfusion interval(s); TSN 5 transfusion sequence number; WBP(s) 5 whole blood platelet(s). From the 1 Etablissement Franc ¸ais du Sang Bourgogne- Franche-Comt e, Dijon, France; 2 CHRU Besanc ¸on, Centre d’Investigation Clinique Inserm CIC1431; 3 CHRU Besanc ¸on, Service d’H ematologie Clinique; 4 Inserm UMR1098, Etablissement Franc ¸ais du Sang, Universit e Bourgogne- Franche-Comt e; and 5 Universit e Bourgogne Franche-Comt e, EA4266 Agents Pathoge `nes et Inflammation, Besanc ¸on, France; and 6 Etablissement Franc ¸ais du Sang Pyr en ees M editerran ee, Toulouse, France. Address reprint requests to: Audrey Seigeot, EFS Dijon, 2 rue Ang elique Ducoudray 21000 Dijon, France; e-mail: Audrey. JINSEIGEOT@efs.sante.fr. This research received funding from the Association Recherche et Transfusion in French. Received for publication May 2, 2017; revision received January 12, 2018; and accepted January 25, 2018. doi:10.1111/trf.14592 V C 2018 AABB TRANSFUSION 2018;00;00–00 Volume 00, Month 2018 TRANSFUSION 1