That sticky, colorless stuff in blood that makes it clot could become scarcer for chemotherapy, radiation and transplant patients who need regular transfusions.
The federal government wants to overhaul the guidelines for platelet donations to ensure donors are protected. Donation center officials say the changes could have an unintended consequence: as much as a 50 percent reduction in the supply.
They have flooded the Food and Drug Administration with letters of opposition, some running dozens of pages.
The government wants to limit annual platelet donations to 24 pints per donor. Now, the limit is on how often someone can donate - 24 times a year. That could equal 72 pints a year since donors can give up to three pints at a time.
Platelets, with just a five-day shelf life, are transfused almost immediately. They are chronically scarce.
The blood officials fear the changes to the 18-year-old guidelines would mean a 10 percent to 50 percent drop in the volume of donated platelets, which are vital for patients who can't make them on their own. During chemotherapy, cancer patients can require six pints to eight pints of transfused platelets a day for weeks.
The FDA's rationale and timing are coming under question.
"At a time when the supply is tight and for what reason? The FDA did not provide us with the information that tells us why," said Dr. Louis Katz, executive vice president for medical affairs at the Mississippi Valley Regional Blood Center in Davenport, Iowa.
Dr. Jay Epstein, director of the FDA's Office of Blood Research and Review, said the proposal is intended as a recommendation. But donation officials said they would view it as a requirement.