The oldest blood available for transfusions releases large and potentially harmful amounts of iron into patients' bloodstreams, a new study by researchers at Columbia University Medical Center (CUMC) has found.
Based on the new findings, the researchers recommend that the FDA reduce the maximum storage limit of red blood cells from 6 weeks to 5 weeks, as long as there are sufficient blood supplies available. "Our recommendation will be controversial, but we think we have real data to support it," said the study's co-leader Dr. Steven Spitalnik, professor of pathology & cell biology at CUMC. "Recent studies have concluded that transfusing old blood has no impact on patient outcomes, but those studies didn't exclusively examine the oldest blood available for transfusions. Our new study found a real problem when transfusing blood that's older than 5 weeks."
In the study, the researchers randomly assigned a group of 60 healthy volunteers to receive a unit of red blood cells that had been stored for 1, 2, 3, 4, 5, or 6 weeks. The volunteers were then monitored for 20 hours after transfusion. Within hours after transfusion, 7 of the 9 volunteers who received the 6-week-old blood could not appropriately metabolize the damaged cells, thereby releasing large amounts of iron into their bloodstream. Only one volunteer who received younger blood had a similar response, with blood that had been stored for five weeks. "Based on the amount of iron circulating in the blood of the volunteers who received 6-week-old blood, we'd predict that certain existing infections could be exacerbated," said Dr. Eldad Hod, associate professor of pathology & cell biology at CUMC.
The true impact of 6-week-old blood on the rate of complications in patients is likely to be small, the researchers say, but since millions of Americans receive transfusions each year, even a 1% difference in complications could affect a large number of patients.