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Donor platelet variation does not affect transfusion outcomes
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Variations in donor platelet function did not affect the outcome of prophylactic transfusions among patients with hematologic disorders, according to a semi-randomized, double-blind study published in Blood.
These results support policies of not selecting donors based on platelet function for prophylactic platelet transfusion.
“In the first controlled trial to assess whether differences in the level of platelet responsiveness in the donor population affect clinical outcome, we have shown that the outcome from prophylactic platelet transfusion in hematology patients does not differ whether the donor of the platelets has very low or highly responsive platelets to agonists in vitro,” Rebecca A. Cardigan, PhD, FRCPath, head of components development at NHS Blood and Transplant at University of Cambridge in the United Kingdom, and colleagues wrote.
To reduce the risk for bleeding among patients who have developed thrombocytopenia as a result of treatment for hematologic malignancies, most platelets are transfused prophylactically on the basis of platelet count. However, little attention has been paid to the affect of donor-related variation on patient outcomes.
Researchers assessed whether platelets collected from donors with highly responsive platelets to agonists in vitro — assessed by flow cytometry — are cleared more quickly from circulation than those from low-responder donors, resulting in lower platelet count increments following transfusion.
The analysis included patients aged 16 years or older with thrombocytopenia secondary to bone marrow failure who required prophylactic platelet transfusion. Researchers randomly assigned 47 patients to receive a platelet donation from a high- or low-responder donor when both were available. Researchers assigned 53 patients to one type of platelet when only one was available.
In total, 51 patients received platelets from low-responder donors and 49 patients received platelets from high-responder donors.
Platelet count increment at 10 to 90 minutes following transfusion served as the primary outcome.
Mean 1-hour platelet count increments were 23.3 x 109/L (95% CI, 7.8-38.9) among patients with low-responder donors and 21 x 109/L (95% CI, 4.0-37.2) among patients with high-responder donors, which did not represent a significant difference (difference, 2.3; 95% CI, –1.1 to 5.7).
Researchers also did not observe a significant difference at 24 hours (high-responder donor, 12.9 x 109/L vs. low-responder donor, 14.31 x 109/L; difference, 1.41; 95% CI, –1.96 to 4.78).
There also was no difference between patients receiving platelets from high- or low-responding donors for clinician-assessed bleeding scores (OR = 0.78; 95% CI, 0.29-2.16) and number of days with a grade 2 to grade 4 bleed (RR = 0.7; 95% CI, 0.16-2.97).
“The results from our study add to those conducted in healthy subjects and suggest that the ability of platelets to survive in the circulation following transfusion to patients is not related to how responsive the platelets of the donor are,” Cardigan and colleagues wrote. “Although the study was not powered with bleeding as the primary endpoint, these data indicate that in addition to there being no difference in the survival of platelets following transfusion between groups, the ability of platelets to prevent bleeding was also not different.”
Researchers noted results may not be generalizable because they assessed stable nonbleeding patients requiring platelets for prophylaxis.
“We cannot extrapolate these data to patients actively bleeding at the time of transfusion, where the immediate hemostatic effectiveness of platelets might be more important than the ability to remain in the circulation,” Cardigan and colleagues wrote. “It is conceivable that platelets from high-responder donors could be the product of choice for bleeding patients, but this can only be elucidated by further research.” – by Chuck Gormley
Disclosures: The National Institute for Health Research (NIHR), NHS Blood and Transplant, and NIHR Cambridge BioResearch funded this study. The authors report no relevant financial disclosures.
Perspective
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Jed B. Gorlin
Quality mavens would have you believe that lack of variation (ie, consistency of a measure) is a sign of higher quality and efforts should be made to eliminate variation. Indeed, W. Edwards Deming — who developed the Total Quality Management approach and is considered the father of modern quality — described variation as “a disease that results in waste and poor quality.”
Although this might be eminently valid for ball-bearing manufacturing, those of us caring for patients and donors recognize that they come in all shapes and sizes and, not surprisingly, vary across many measures. With respect to apheresis platelet donors, collection facilities routinely select for donors with higher baseline counts to minimize time that the donor needs to stay in the donor chair and to maximize yield in order to get double and even triple collections.
Although some platelets are transfused to acutely bleeding patients typically for trauma or surgeries, many are given prophylactically to patients with hypoproliferative conditions (eg, patients with cancer after chemotherapy or following a transplant). In these settings, it is desirable to have platelets with greatest potential for survival and, hence, screening platelets for activation has been proposed, as less activated platelets may circulate longer.
Although level of platelet activation may be a function of both apheresis platelet collection platform, as well as postcollection modifications — including leukoreduction filtration — it has also been shown to be a reproducible trait of donors. Specifically, some donors appear to have platelets for whom platelet activation markers are consistently low, and other donors are consistently high. Therefore, at least one company is offering a testing tool to screen for platelet microparticles and other activation measures.
Before considering adopting such screening tools — and potentially even further diminishing our aging platelet donor base — a group from Cambridge, United Kingdom, in collaboration with the NHS blood collection agency, studied practical effects on both 1-hour and 24-hour platelet count increments, as well as other secondary measures of bleeding.
Simply put, when researchers compared almost 50 patients who received platelets from donors with higher levels of activation with a similar number who received less activated platelets, results showed no statistically significant differences in platelet count increments or any of the secondary measures. They did not even observe trends to suggest further study might be warranted. This should put the nail in the coffin for proposals to further complicate provision of platelets on the basis of donor platelet function.
HemOnc Today Editorial Board Member
Innovative Blood Resources, St. Paul, Minnesota
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