Drs. Goodnough and DiPersio present an authoritative and informative discussion of the management of thrombocytopenia in the cancer patient, emphasizing the risks of platelet transfusions, the safety of a platelet count threshold of < 10,000/µL for prophylactic transfusions, and issues related to the optimal type of platelet product and dose of platelets. The authors make the important point that although the risk of transmission of viral infections has decreased markedly due to the addition of nucleic acid testing for hepatitis C and human immunodeficiency virus (HIV), sepsis due to bacterial contamination remains a serious risk, particularly for the neutropenic patient. The fever and chills that occur within 6 hours after a platelet transfusion usually are associated with nonhemolytic febrile transfusion reactions, but the more dangerous possibility of bacterial sepsis from contamination should be considered, particularly in the neutropenic patient, and treated empirically until bacterial cultures prove otherwise.
Although efforts are being made to develop timely automated systems to detect contaminating bacteria, it is more likely that pathogen inactivation methods will be the future mode of eliminating these organisms from platelet components. Currently, a randomized trial is studying the clinical efficacy of platelets that have been treated with the synthetic psoralen compound amotosalen hydrochloride and long-wavelength ultraviolet lighta process that inactivates HIV and hepatitis C virus, as well as bacteria and protozoa. Obviously these methods will increase the cost of platelet transfusions even further. However, the 26% mortality associated with recognized bacterial infections and the likelihood that platelets are a source of many unrecognized bacterial infections support encouragement of these efforts.
The authors stress that the threshold of < 10,000 platelets/µL for prophylactic platelet transfusion continues to be shown to be safe and leads to a reduction in the use of platelet transfusion. The data in Figure 1 of the Goodnough/DiPersio article, from a multicenter transplantation study published in 1998, appear to show that almost two-thirds of the patients received platelet transfusions prompted by the higher < 20,000/µL threshold. The problem, of course, is not just that old habits (the 20,000/µL trigger) die hard, but that other factors such as infection, fever, and a rapid rate of decline in platelet count influence clinicians to follow a more liberal platelet transfusion policy in individual patients. Indeed, many controlled studies investigating the lower platelet count threshold have used the higher threshold in patients with these complications.
The effect of these factors on corrected platelet increments supports the clinical impression that more platelets are required in these settings. Other issues include concerns regarding the accuracy of automated measurements of very low platelet counts (due to red cell fragments that are counted), although the reliability of automated platelet counts has improved significantly in recent years.
The American Society of Clinical Oncology (ASCO) recently published guidelines for platelet transfusion therapy in patients with cancer, based on evidence from published trials and reports and the opinions of an expert panel. Many of the points made by Drs. Goodnough and DiPersio are reflected in the ASCO guidelines, which are briefly summarized here: