NEW YORK – Rotating stock of red blood cells so that the oldest supply is used first might help reduce waste but isn’t optimal for patients, according to a new study.

In fact, the report in the Journal of Clinical Investigation, suggests that the oldest blood available for transfusions releases large and potentially harmful amounts of iron into patients’ bloodstreams. As a result, the study team, led by Columbia University Medical Center researchers, recommends reducing the maximum blood storage limit from six to five weeks, assuming sufficient blood supplies are available.

“Our recommendation will be controversial, but we think we have real data to support it,” said the co-lead investigator Steven Spitalnik, MD, professor of pathology and cell biology at Columbia University Medical Center (CUMC) and medical director of the clinical laboratories at New York-Presbyterian/Columbia. “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 five weeks.”

Background information in the article notes that transfusion of red blood cells is the most common procedure performed in hospitalized patients, with approximately 5 million patients receiving red blood cell transfusions annually in the United States.

For the study, the research team 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, monitoring them for 20 hours after transfusion.

Within hours after transfusion, seven of the nine volunteers who received the six-week-old blood could not appropriately metabolize the damaged cells, releasing large amounts of iron into their bloodstreams. Among those receiving blood stored for five weeks, only one volunteer had a similar response.

While none of the volunteers suffered longer term harm from the transfusions, previous studies have shown that excess iron can enhance blood clots and promote infections, according to study authors.

“Thus, for ill, hospitalized patients, this excess iron could lead to serious complications,” Spitalnik explained.

The study concedes that the effects of six-week-old blood on the rate of complications in patients are likely to be small, but could be significant across the large number of patients receiving transfusions.

“It’s estimated that up to 10 to 20 percent of blood units used for transfusions have been stored for more than five weeks, so the number of patients who are likely to receive a unit of very old blood is substantial,” pointed out co-lead investigator Eldad Hod, MD, associate professor of pathology and cell biology at CUMC.

“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,” added Spitalnik. “The U.K., Ireland, the Netherlands, and the National Institutes of Health have limited storage to 35 days, and we think that can be achieved throughout the U.S. without seriously affecting the blood supply.”