Chilled platelets could extend bleeding care to 21 days, trial finds

At a Vitalant donation center in Pittsburgh, a platelet donation begins with blood flowing through a tube to a machine that keeps the platelets and returns the rest to the donor. The product normally lasts only 5–7 days at room temperature. A clinical trial led by University of Pittsburgh physician-scientists now reports that chilled platelets remained as effective against bleeding when stored for up to 21 days.

The Chilled Platelet Study enrolled 1,000 adults, children and babies undergoing cardiac surgery at 27 sites in the U.S. and Australia from December 2021 to March 2025. Patients received either standard platelets stored at room temperature for less than seven days or refrigerated units. After every 200 participants, independent analysts checked whether the chilled product was performing as well; if it was, the trial extended the maximum age of the units tested by five days, up to 21 days.

That result challenges an assumption formed from early studies in healthy volunteers half a century ago: regulators had believed refrigeration made platelets less effective. Recent preclinical work pointed in the opposite direction. In this trial, chilled platelets stored for as long as three weeks treated bleeding as effectively as standard platelets stored for up to one week. Because blood banks can take two days to process donations, the finding could extend the usable lifespan of the therapy by almost fourfold.

The practical pressure is visible in the current supply. Of the 2.5 million room-temperature platelet units collected each year in the U.S., roughly 10% to 20% are wasted because they expire, at a cost of $300 million to hospitals. More than 97% of platelets come from apheresis, the collection method used at Vitalant, and younger donors are not replacing older donors quickly enough to keep pace with demand.

So what changes, concretely? A longer shelf life could make it easier for rural and community hospitals to keep platelets on hand instead of accepting waste they cannot afford. It could also help hospitals absorb sudden surges in need. The FDA and regulators in multiple countries are considering changes for refrigerated platelets, but the existing rules have not yet been revised; the trial’s results are those reported by the research team and published in JAMA.