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Infection Risk From Blood
By: Daniel DeNoon Reviewed By: Brunilda Nazario, MD WebMD Medical News Archive Archive Aug. 18, 2004

You've now got a near-zero chance of getting HIV or hepatitis C from a blood transfusion or tissue graft, new studies show. But is this extra safety worth the extra cost?

In the early 1980s, there wasn't any way to tell whether a blood transfusion carried the deadly AIDS virus. What saved the day were antibody tests. These tests showed whether a blood donor's body was mounting an immune response against HIV. A similar test for hepatitis C virus also made blood safer.

But a dangerous window remained open. If people donated blood or tissues after getting a virus infection but before their bodies mounted an antibody attack on the virus, the tainted blood could not be detected. Now, a new technology -- nucleic acid testing -- is used to test donated blood and tissue for a virus' genetic material.

How well are these tests working? Very well, according to two reports in the Aug. 19 issue of The New England Journal of Medicine. An editorial by Jesse Goodman, MD, MPH, director of the FDA's Center for Biologics Evaluation and Research (CBER), accompanies the reports.

"I think the biggest message here is the tremendous advance in blood safety from HIV and hepatitis C virus, which are probably the two most serious illnesses that can be potentially transmitted by blood," Goodman tells WebMD. "What has happened here is in the space of just 20 years since HIV and hepatitis C virus were really infecting significant numbers of blood donors -- with pretty tragic consequences -- first we had pretty effective antibody tests, which dramatically improved blood safety, and now on top of that we have a new test. [These tests] now make the risk of getting HIV or the most serious hepatitis virus one in 2 million."

Blood Safety

Susan L. Stramer, PhD, executive scientific officer for the American Red Cross, led a team that analyzed tests of some 37.2 million units of blood.

The result: Nucleic acid tests showed that 12 units of blood -- which passed antibody tests -- actually carried HIV. The tests detected 170 units infected with hepatitis C.

"For HIV we are talking about a rare event: One in 3 million donors is positive [on a nucleic acid test] prior to having detectable antibody," Stramer tells WebMD. "For hepatitis C virus, we tested 39 million units of blood. One in a quarter of a million was hepatitis C nucleic acid test-positive prior to appearance of detectable antibody."

Tissue Safety

D. Michael Strong, PhD, executive vice president at the Puget Sound Blood Center/Northwest Tissue Center in Seattle, led a similar study of tissues donated by 11,391 donors to five U.S. tissue banks.

They used nucleic acid tests to look for four dangerous viruses: HIV, hepatitis C virus, hepatitis B virus, and HTLV, a cancer-causing retrovirus.

The results: The chance that nucleic acid tests would find previously undetected infection was one in 55,000 for HIV, one in 42,000 for hepatitis C, one in 34,000 for hepatitis B, and one in 128,000 for HTLV.

Strong notes that just because a tissue carries a virus, it doesn't mean a person who gets a graft from that tissue will become infected.

"This doesn't say what the risk is from any given tissue, although there are different risks from different tissues," Strong tells WebMD. "But with the advent of nucleic acid testing for blood, it seems obvious to use this technology to increase the safety of donated tissues."

The higher risk of undetected virus in tissues is likely due to the donation process, suggests Margery Moogk, director of the Northwest Tissue Center in Seattle.

"The first step in determining donor suitability is the screening interview where we look at a person's medical and social history to determine the risk of that person being exposed to a disease," Moogk tells WebMD. "With blood donors, you ask the person. With [cadavers], we are talking to the family members or partners to discern what that history is. So there's a difference between tissue donors and blood donors, in terms of the tissue donor slipping through the testing as a false negative. That may make nucleic acid testing more important in tissue donation than in blood donation."

The Cost of Extra Safety

Stramer's data show that nucleic acid tests prevent five HIV infections and 56 hepatitis C infections every year. The cost: $1.5 million to $4.3 million per year of life saved.

That cost is likely to go up as a nervous public demands more tests for more diseases.

"These tests come at a high price. As we add more and more tests, someone has to pay," Stramer says. "We probably have reached the point that the hospitals that purchase our products say our blood is safe enough. We have focused so long on this unit of blood, when we might better serve patients with a focus on the rest of the process -- hospital errors and things like that. There are many other dangers to a patient in the hospital besides the risk of infection from a blood transfusion."

Strong and Moogk note that the added costs for tissue testing aren't as great because each donation usually goes to multiple recipients. And people getting a bone graft in their knees, for example, are less willing to risk a lifelong viral infection than a person whose life depends on a blood transfusion.

The FDA's Goodman agrees that cost is a major issue.

"As we make blood or tissues safer and safer from various infectious agents, it can become at times increasingly expensive to deal with that last bit of risk," he says. "It is a good idea to have a very public discussion about what kinds of investments make sense. ... We don't want it to become where the cost is so great it limits the availability of lifesaving therapies. We need to get that right."

Goodman notes, however, that new technologies may eventually lower the cost of testing blood for multiple infections. And he asks Americans to remember that the best way to ensure blood and tissue safety is already at hand.

"An important thing that makes our blood and tissues safe and available is the public's goodwill and willingness to donate," he says. "A robust volunteer system is a safer system."