The government approved sophisticated genetic fingerprinting tests Thursday for blood banks to use to further reduce the risk of dangerous viruses slipping into transfusions.
The vast majority of transfusions already are infection-free. But blood banks have been performing this nucleic acid testing, called NAT, as part of a nationwide experiment since 1999 to see if the more sophisticated method can make the blood supply even safer.
Thursday's approval by the Food and Drug Administration validates NAT testing as adding that extra layer of safety.
can detect tiny amounts of the AIDS virus or liver-destroying hepatitis C before the blood donor's body has even recognized the infection. Some of the tests can detect as few as 10 copies of a viral gene.
Viral genes spread through blood faster than the immune system begins forming antibodies to fight them, a reaction that may not occur until 20 to 80 days after the person is infected. Yet until now, blood testing has depended largely on tests that detect antibodies in an infected donor. So newly infected donors occasionally slip through.
Adding nucleic acid testing to the standard battery of blood tests promises to close much of that gap. In the nationwide studies, nucleic acid testing of an estimated 20 million blood donations caught seven cases of HIV infection and 88 hepatitis C-positive donations blood that otherwise would have slipped through.
Chiron Corp. makes the newly approved test, which it sells under the brand name Procleix.