AAMC Reporter: December 2007

As Blood Donor Pool Thins, Research and Outreach Become Key

Advances in scientific research often come step by step, with new findings building incrementally on prior knowledge. Once in a while, though, a paper appears that shakes common wisdom down to its roots.

This summer, a study led by the University of Minnesota Medical School shattered basic assumptions about the national pool of blood donors. Publishing in the July 2007 issue of the journal Transfusion, William Riley, Ph.D., Matthew Schwei, M.P.H., and Jeffrey McCullough, M.D., found that the conventional method of calculating the size of the national pool of potential blood donors has been overestimating the national number of eligible donors by a striking 59 percent.

The effect, they said, was that instead of the 177 million Americans previously thought to be eligible blood donors, only 111 million individuals are in fact eligible. McCullough, a professor in the medical school's department of laboratory medicine and pathology, said there was a straightforward reason for the precipitous drop.

"Tests and steps that have been put in place over the last 25 years to improve blood safety have done an outstanding job," he said. "But at the same time, they have eliminated a very large number of people from the potential donor pool in the United States."

Until the Minnesota study, though, no one had looked at the aggregate effect of the more stringent screening.

"A lot of the statistics that have been used for years, trying to estimate the number of eligible donors and therefore how many people were giving per eligible population, have been based only on age. We knew that was going to be a problem," said Christopher Hillyer, M.D., a pathology and laboratory medicine professor at Emory University School of Medicine and past president of AABB (formerly known as the American Association of Blood Banks).

Using a demographic model, Hillyer said, the study investigators looked at "not just age as an exclusion criteria, but also heart disease, diabetes, and all the other travel and infectious disease risks."

The Minnesota study certainly caught the attention of national experts. The blood banking community had been saying "that 60 percent of the population was eligible to donate blood," said Stephanie Millian, director of biomedical communication at the American Red Cross national headquarters in Washington, D.C. "But the new data suggest that the eligible donor pool is substantially smaller than that, representing less than 38 percent of adults ages 18 to 65."

On top of that, experts have been estimating that as few as 5 percent of potential donors actually give blood.

The Minnesota study also had an impact among those who toil to collect blood pint by pint. Rebecca Hileman is assistant director for education and business development in the Blood Donor Services department at Inova Health Systems, a large health care provider and teaching hospital based in Northern Virginia that is looking to broaden its donor base.

One goal at Inova, Hileman says, "is to have a donor population that more fairly reflects our patient population."

Now, though, while Inova's patients mirror the region's ethnic diversity, most blood donors are Caucasian. Inova is reaching out to diversify its donor pool. The hospital works avidly, for example, to convince local African American and Latino community leaders, ministers, and store owners about the importance of giving blood. The theory is that if they persuade opinion leaders, those leaders will in turn influence members of their communities to donate.

The national Red Cross has been following a similar strategy with community leaders.

"The face of America is changing, and the Red Cross needs to change with it," Millian said. "We need to start collecting blood from other populations than we have in the past."

Inova staff spend long hours, too, in local schools, educating young people about the importance of donating blood and hoping to create lifetime donors. They also try to boost their success with repeat donors. (Red Cross statistics show that its donors give blood an average of 1.6 times per year.)

Targeting youth at the national level, the Red Cross has partnered with the Ad Council, the AABB, and America's Blood Centers, representing community-based blood centers, on a marketing campaign called "Save the World." Similarly, the Red Cross also works with the National Association of Intercollegiate Athletics.

Still, blood supplies overall remain tight. In the second week of September, for example, a color-coded chart on the Inova Web site showed less than one-day supplies for all blood types except one, AB positive. As Stephanie Millian observed about blood supplies nationally, "we have less people available to donate blood right now, and the industry itself is painting itself into sort of a corner by deferring more and more people each year. Because of this, blood is becoming an even more precious resource each and every day."

Recent research has given the blood community a better understanding of what motivates blood donors.

"We have studied for a long time why people do and don't donate," Hillyer said. "It pretty much boils down to the same thing, regardless of where in the world you are. Basically, people want to be asked to donate. They want to have a good donation experience that's convenient and timely. And then they want to be thanked for donating in a way that works for them."

Discussions of blood donations—and news stories about threats such as HIV and the West Nile virus—inevitably raise questions about the safety of the blood supply. Here, there is good news to report.

"What people like to say is that the blood supply has never been safer, or is safer than ever, and that is, of course, true," Hillyer said. "There have been dramatic improvements made in the last 25 years through the implementation of new screening questions and donor tests. Some of the numbers really back that up in important infectious diseases."

For example, he said, the risk that blood units could transmit HIV was once considered as high as 1-in-100 to 1-in-1,000 units, but now is on the order of 1-in-2-million to 1-in-5-million units.

One focus of current blood safety research is a disorder called transfusion-related acute lung injury (TRALI), a complication sometimes seen after blood transfusions. Recent findings suggest a possible correlation between TRALI and blood donations from females. That led the AABB, Hillyer said, to recently suggest that "plasma from female donors would be preferable for use in the preparation of life-saving medications, while plasma for transfusion should come predominantly from male donors."

Moreover, Hillyer said, "other countries, such as the United Kingdom, have moved to male-only plasma products. A question for researchers is whether the United States should follow suit."

Among other ongoing studies, Hillyer said, researchers are investigating the criteria for determining appropriate patient doses of blood.

"Since 1980," he said, "we have tried to give blood more sparingly because we were worried about things like HIV, West Nile, and hepatitis. Now, with the blood supply being screened and as safe as it is, it may be time to ask [whether] we should liberalize the amount of transfusion in certain patient populations." Hillyer said he is aware of yet unpublished data from battlefield clinics in Iraq that suggest that "in trauma and massive injuries, to give plasma components earlier helps saves live."

Emory, for instance, plans to review its protocols for what are called massive transfusions—to make sure, as Hillyer said, that "the pendulum is in the right place."

And what about artificial blood—does that offer any promise? Volunteering that he has been fielding such questions for more than 20 years, Hillyer suggested that the science for what researchers call blood substitutes has yet to produce results that could alleviate blood shortages.

—By Stephen Pelletier, special to the Reporter

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