Red Cross Uses Nucleic Acid Testing to Screen Donor Blood for Transfusion-Transmitted Viruses

The American Red Cross is investigating a new genetic test, nucleic acid testing (NAT), for the early detection of transfusion-transmitted viruses, such as HIV and hepatitis C virus (HCV), at its National Genome Testing Laboratory (San Diego). The new technology 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 has already used NAT to detect HCV-infected donor blood that was negative by standard screening tests, thus preventing a probable transmission of the disease.

The Red Cross 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.

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% and for HCV, about 41 days, which NAT should shorten by 50 to 98%.

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.

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.

The American Red Cross is a supplier of blood, plasma, and tissue products.

For more information: American Red Cross, Public Inquiry Office, 11th Floor, 1621 N. Kent Street, Arlington, VA 22209. Tel: 703-248-4222. Email: info@usa.redcross.org.