Technology Offers Potential to Further Protect U.S. Blood Supply
Washington, DC, April 8, 1999 -- The American Red Cross is pioneering the use of an innovative technology that could add an additional layer of safety to the 14 million units of blood components distributed by the Red Cross to hospitals nationwide each year. The Red Cross is investigating a new genetic test, nucleic acid testing or NAT, for the early detection of transfusion-transmitted viruses, such as HIV and Hepatitis C Virus (HCV), at its National Genome Testing Laboratory in San Diego, Calif. Already the Red Cross' use of NAT has detected the first unit of HCV-infected donor blood that was negative by standard screening tests, thus preventing a probable transmission of the disease.
The Red Cross has been the leader in bringing NAT technology to blood screening and began evaluating NAT under an Investigational New Drug (IND) application approved by the Food and Drug Administration (FDA) in January 1999. Initially the Red Cross performed unlinked testing, severing the link between the donor and sample, to validate the processes and systems newly created for NAT. Red Cross tested more than 180,000 samples during unlinked testing.
Based on favorable test outcomes, the Red Cross began screening blood donations with NAT at the National Genome Testing Laboratory under the FDA-approved IND in early March 1999. The Red Cross expects to fully implement NAT under the IND in all of its blood centers by June 1999.
"While the U.S. blood supply is already safer than it ever has been and current screening tests are very sophisticated, this innovative technology has the potential to enable the detection of dangerous viruses in donors whose own immune systems have not yet recognized the presence of an infectious agent," says Brian McDonough, chief operating officer, American Red Cross Blood Services. "This new screening method is expected to provide more accurate and earlier identification of virally infected blood."
Because NAT looks directly for the genetic material of viruses, either DNA or RNA, the test can detect an infectious agent's presence much earlier than current screening tests. Most available tests detect the antibodies formed as part of the immune response to a virus, often 20 days to 11.5 weeks after infection. NAT may decrease the time after initial donor exposure to when detection is possible. For HIV, this time is usually six to 10 days after exposure, which NAT should reduce by 30 to 50 percent and for HCV, about 41 days, which NAT should shorten by 50 to 98 percent.
While the Red Cross' testing of NAT focuses on HIV and HCV, the test can be tailored for future use to screen for other blood-borne pathogens and for newly emerging viruses, bacteria or fungi for which genetic material has been identified.
The Red Cross estimates that rates of NAT-reactive donations among those volunteer donors that test negative by currently performed screening tests for HIV and HCV are one per million donations for HIV and one per 100,000 for HCV.
"By adapting technologies like NAT, the American Red Cross is continuing in its mission to develop ways to improve the safety of the U.S. blood supply and reduce the risk of disease transmission through blood products," says Richard Davey, M.D., chief medical officer of the Red Cross.
Approximately 4 million people annually receive blood or blood products as part of their medical or surgical care in the United States. Blood centers have implemented several overlapping strategies to safeguard the nation's blood supply-- including screening of the donor and viral testing of donations-- to reduce the transmission of virally infected blood. However, a small risk of transmission of viral infection through blood transfusion remains because of donations during the so-called "window period" in which antibodies have not yet formed despite the donor's exposure to the virus.
Gen-Probe Incorporated of San Diego, Calif., developed and manufactures the semi-automated NAT kits used by the Red Cross. Under an agreement with the Red Cross, Gen-Probe and Chiron Corporation of Emeryville, Calif., will provide instruments and NAT kits for the Red Cross testing.
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The American Red Cross is the nation's largest supplier of blood, plasma and tissue products in the United States. The Red Cross supplies almost half of the U.S blood supply by working with more than 4.5 million donors and 3,000 hospitals through its national network of 37 blood regions. In addition, the Red Cross supplies one-quarter of the nation's tissue for transplantation through its network of 18 tissue centers nationwide.