Platelet transfusion practices often are based on historical patterns rather than current data. In a session (9228-TC) held Oct. 10 at the 2010 AABB Annual Meeting and CTTXPO, a panel of experts showed why some of these practices should be reconsidered. Audience members had the opportunity to immediately apply the information they learned, as they were asked whether they would approve a platelet request in different clinical situations.
Neil Blumberg, MD, director of the clinical laboratories at University of Rochester Medical Center, started off the session by emphasizing that ABO identical platelet transfusions yield better results for both patients receiving their initial therapy and refractory patients, and with positive and negative crossmatches. He also diminished the notion of ABO-“compatible” platelet transfusions, pointing to a study that showed corrected count increments for patients receiving identical ABO platelets were significantly higher than those given unmatched products, but the difference in CCI for compatible versus incompatible platelets was insignificant.
ABO-identical transfusions are the gold standard, he added, as mismatched platelet transfusions have been associated with increased morbidity and mortality in open heart surgery, stem cell transplantation and acute leukemia treatment.
Steven Kang, MD, assistant pathology professor at the State University of New York Downstate Medical Center, presented three cases of thrombocytopenia and asked the audience to decide whether the patients should be given platelets. These cases included a woman with iron-deficient anemia, a man with malignant hypertension and a teenage girl with lupus nephritis — and Kang demonstrated that contrary to conventional wisdom, these patients may not need platelet transfusions.
Joseph Sweeney, MD, director of transfusion medicine and coagulation at Brown University, continued exploring the nuances of platelets. For one, he said that platelet size and count are inversely related, so that people with smaller platelets often have a greater number of them, and vice versa. In general, women have more platelets than men, and Caucasians have more than African-Americans.
A common misconception about platelets, Sweeney said, is that there is a linear relationship between a low count and the risk of bleeding. However, new data show that the relationship is exponential, meaning that people with a very low platelet count have a very high risk of bleeding, but those with a moderate count have very little risk. Because of this, patients with an average or even low (but not dangerously low) count undergo unnecessary platelet transfusions.
Sweeney insisted that “the devil is in the details about when to transfuse.” In the case of biopsy patients, the size of the needle, the skill of the clinician and the patient’s underlying condition all influence bleeding and whether platelets are necessary.
Jay Herman, MD, director of transfusion medicine at Thomas Jefferson University in Philadelphia, finished the session with a discussion about platelet product and dose. The component itself, he said, has changed over the years.
“It’s amazing how many people don’t know what’s in the bag,” he said. “It’s not your mother’s platelets anymore.” Now, there can be pooled, prepooled and pheresis platelets, all with different volume levels, amount of red cells and other distinguishing features. Platelets, he said, did not used to be leukoreduced; now, “universal leukoreduction makes sense.”
With respect to platelet dosage, the recent PLADO trial found that among participants with low platelet counts due to poor bone marrow function, bleeding incidence and severity were dose-independent. These results “[flew] in the face of the traditional literature,” which has generally found that transfusing different dosages does affect outcomes, Herman said.
By educating attendees on these preconceptions about platelets, the speakers said they hoped to foster a better understanding of when, how much and what types of platelets to transfuse.
— Elissa Fuchs