Window Period: The time between donor exposure to the virus and the appearance of antibodies.
NAT significantly reduces the window period, the time between initial infection of HCV or HIV-1 and when the virus is first detectable, in comparison to antibody tests.
Studies have shown that NAT can detect Hepatitis C in blood donated by someone who contracted the disease 14 to 28 days prior to donating, whereas previous tests detected the virus after about 70 days.
Previous studies indicate that this technology can detect low levels of HIV-1 in blood donated by someone who contracted the disease three to five days earlier than current tests. Current tests have a window period of about 16 days.
NAT is used in addition to other tests because it is possible for infected individuals to be NAT-negative if their virus falls below detectable levels, and yet, still test positive using antibody procedures.