PCR and Blood Screening

Since the 1970s serological tests have been used to screen donated blood samples for the presence of infectious agents. Nevertheless, a small risk of viral transmission remains primarily due to the failure of such screening tests to identify recently infected donors during the "window period" - the time delay post-infection in which the body develops an immune response to the infectious agent. Tests using PCR nucleic acid amplification testing (NAT) technology detect the actual virus. Experts believe that including such tests in blood screening programs could provide an added measure of protection by detecting viral infection at an earlier stage.

Highly sensitive PCR-based tests are available for detecting early markers of HIV-1, hepatitis B and hepatitis C infection, namely viral DNA or RNA, in blood. These tests are helping to narrow the "window period" resulting in improved blood safety. Benefits of using PCR technology to monitor the world's blood supply include:

• A decrease in the waiting period or "window period" during which the infectious agent is undetectable by traditional screening technologies that rely on the formation of antibodies
• The ability to perform comprehensive and combined blood screening for several pathogens, including hepatitis C, hepatitis B and HIV-1. Combination PCR-based tests incorporated into blood donor screening programs could dramatically reduce the risk of virus transmission¹

¹Blood Safety in the New Millennium, published by the American Association of Blood Banks, 2001