Transfusions of blood that has been stored for 6 weeks can release large and potentially harmful amounts of iron into patients’ bloodstreams, a new study suggests.
Based on these findings, researchers are recommending the US Food and Drug Administration (FDA) reduce the maximum storage limit of red blood cells (RBCs) from 6 weeks to 5 weeks, as long as there is a sufficient supply of blood.
“Our recommendation will be controversial, but we think we have real data to support it,” said study author Steven Spitalnik, MD, of Columbia University College of Physicians and Surgeons — New York Presbyterian Hospital in New York, New York.
“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.”
Dr Spitalnik and his colleagues described their study in The Journal of Clinical Investigation.
The researchers randomly assigned a group of 60 healthy volunteers to receive a unit of RBCs that had been stored for 1, 2, 3, 4, 5, or 6 weeks. The volunteers were then monitored for 20 hours after transfusion.
The researchers found that a longer duration of RBC storage was associated with a progressive increase in extravascular hemolysis, decreasing post-transfusion RBC recovery, decreasing elevations in hematocrit, and increasing serum ferritin.
None of the volunteers were harmed by the transfusions, but subjects who received 6-week-old blood had outcomes associated with an increased risk of harm.
In 7 of the 9 subjects who received the 6-week-old blood (78%), the amount of iron entering the circulation exceeded the iron-uptake capacity of transferrin, producing circulating nontransferrin-bound iron. The same effect occurred in 1 of the 10 subjects who received 5-week-old blood (10%, P=0.003).
The area under the curve of the change in nontransferrin-bound iron was significantly higher for subjects who received the 6-week-old blood than for all other subjects (P<0.001). The same was true for serum iron (P<0.01) and transferrin saturation (P<0.001).
“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 study author Eldad Hod, MD, also of Columbia University College of Physicians and Surgeons — New York Presbyterian Hospital.
“Thus, for ill, hospitalized patients, this excess iron could lead to serious complications,” Dr Spitalnik added.
The researchers said the true impact of 6-week-old blood on the rate of complications is likely to be small. However, since millions of Americans receive transfusions each year, even a 1% difference in complications could affect a large number of patients.
“It’s estimated that up to 10% to 20% of blood units used for transfusions have been stored for more than 5 weeks, so the number of patients who are likely to receive a unit of very old blood is substantial,” Dr Hod noted.
“Based on our findings of potential harm, we think the prudent thing to do, at this time, is for the FDA to reduce the maximum storage period,” Dr Spitalnik added.
“The UK, Ireland, the Netherlands, and the National Institutes of Health have limited storage to 35 days, and we think that can be achieved throughout the US without seriously affecting the blood supply.”
This study was supported by grants from the National Institutes of Health (HL115557 and UL1TR000040).
