Cold-stored platelet concentrates showed strong clot-forming activity in laboratory tests, according to data presented at EHA2026. The analysis may help explain why refrigerating these blood components may make them better equipped to support bleeding control.
For now, transfusion of cold-stored platelets remains a situational option rather than routine first-line care for active bleeding. In the U.S., FDA guidance allows these products to be used only when standard room-temperature platelets are not available or their use is not practical.
The findings could help researchers determine whether these blood components deserve a larger role in urgent bleeding scenarios, including severe cases of fetal and neonatal alloimmune thrombocytopenia (FNAIT), in which active hemorrhageFetal hemorrhage Any bleeding that occurs before birth. In FNAIT, this usually results from extremely low platelet counts. may require prompt platelet transfusionPlatelet transfusion A treatment for newborns with very low platelet counts that ideally uses HPA-compatible or washed maternal platelets..
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To study the effect of temperature, researchers followed platelet concentrates for 21 days after pathogen-reduction treatment. Some samples were stored with agitation at room temperature (22°C), while others were stored without agitation at 4°C.
By the one-week mark, the refrigerated samples had developed two new platelet subpopulations. The groups, labeled Intermediate 1 and Intermediate 2, accounted for roughly 7% and 15% of the platelet population, respectively. Neither group appeared in room-temperature samples.
Laboratory tests showed that both groups had aggregation and procoagulant traits, suggesting they may help drive the functional changes seen with cold storage. Imaging experiments added another clue: these platelets spread across surfaces, formed small extensions and became embedded in developing clots under simulated blood flow.
The study does not prove that cold-stored platelets improve outcomes in patients. The experiments were designed to show how storage temperature changes platelet behavior in the laboratory. Researchers also noted that whether similar cell groups arise naturally in the body during bleeding has not yet been shown.
Still, the finding may have implications beyond transfusion medicine, touching on broader questions about how the body stops bleeding and how clots form inside blood vessels. The study authors concluded that identifying these novel platelet groups carries “pathophysiological implications for both transfusion medicine in hemorrhagic patients as well as hemostasis and thrombosis.”
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