CHAPEL HILL - The risk of contracting a virus - including the virus that causes AIDS -- from donated blood in the United States has grown too small to measure and can only be estimated through mathematical techniques, disease specialists say.
On the other hand, too few people donate blood regularly, they say, and the percentage of donors has dropped. With the growing U.S. population also aging, the nation will face an increasing need for transfusions over the next few decades. One likely result will be a serious blood shortage, and more units will need to be imported from abroad.
The first half of a two-part report on progress in transfusion medicine appears in the Feb. 11 issue of the New England Journal of Medicine. The second half will appear next week.
Authors - all transfusion medicine experts -- are Drs. Lawrence T. Goodnough of Washington University, Mark E. Brecher of the University of North Carolina at Chapel Hill, Michael H. Kanter of Southern California Permanente Group and James P. AuBuchon of Dartmouth-Hitchcock Medical Center.
"A lot of people, including most practicing physicians, don't realize that the U.S. blood supply is now extremely safe - so safe it's difficult even to estimate the risk of disease transmission," said Brecher, professor of pathology and laboratory medicine at the UNC-CH School of Medicine. "Because of that high safety level, the effectiveness of donating one's own blood for use during or after an upcoming operation, which does present a small risk to patients, is being called into question."
In 1983, the chance of contracting human immunodeficiency virus, or HIV, from a unit of blood was about one in 100, Brecher said. Because of improved donor screening and tests on drawn blood, now the chance is one in 676,000.
The risk of contracting hepatitis A is one in a million, hepatitis B one in 250,000 and hepatitis C one in up to 150,000.
Bacterial contamination of platelets may pose the highest risk because platelets cannot be refrigerated or frozen like red cells or plasma and must be stored at room temperature for up to five days, Brecher said. But even with platelets -- required by some cancer patients and trauma victims -- the risk is still only one in 12,000 per bag. Many patients receive a pool of six to 10 platelet donations in a single transfusion, and so the actual risk may be six to 10-fold higher per transfusion.
"Since experts have predicted the proportion of the U.S. population over age 65 will double by the year 2030, there will be more operations, more transfusions and substantial demands on the blood supply," the physician said. "Use of transfusions has dropped over the past 20 years largely because of concerns about the safety of donated blood, but that trend will likely change now because of these factors."
Donor trends also have changed significantly since the 1970s. Rates of blood collection - the number of units collected per 1,000 people - peaked in 1987 and declined by 9.3 percent between 1989 and 1994. Contributing factors included the misconception that the AIDS virus could be spread by donating and increased donor rejection through more rigorous screening. Roughly a half million donors are disqualified each year.
According to a 1993 health survey, 46 percent of the U.S. population had donated blood at some time in their lives, but only 5.4 percent donated during 1993, Brecher said. People who donate blood regularly are desirable because they are more easily persuaded to give and have been screened repeatedly for risk factors.
Although an increasing percentage of donors are women, women are less likely than men to give regularly, likely due to decreased iron stores, he said. People over age 65, once discouraged from giving blood, now represent an important and growing source of donations.
Note: Brecher can be reached at 919-966-8465 (w) or 919-933-1548 (h), Goodnough at 314-362-2186.
Journal
New England Journal of Medicine