Nucleic Acid Testing (NAT) is a method of testing blood that is more sensitive than conventional tests that require the presence of antibodies to trigger a positive test result.

On October 25, 1999 Canadian Blood Services implemented NAT screening of all blood donations for Hepatitis C Virus (HCV). On May 28, 2001 it broadened its NAT screening to include NAT screening for HIV-1, the virus that causes AIDS. Canadian Blood Services intends to implement another NAT screen test for West Nile Virus (WNV) on or about July 1, 2003.

NAT works by detecting the low levels of viral genetic material present when an infection occurs but before the body begins producing antibodies in response to a virus.

NAT significantly reduces the 'window period' or the time between donor exposure to the virus and the appearance of antibodies. By decreasing the window period, it allows for earlier detection of the infection and thus further decreases the possibility of transmission via transfusion.

Since implementation of HCV NAT screening, there has been only one "window case" detected, and for HIV-1 NAT there have been no window cases detected as of May 2003.

NAT HCV Scientific Paper Questions and Answers
NAT HIV Scientific Paper pdf: 25K/8 pages
NAT HIV Investigational Project (General Document) and Qs&As pdf: 25K/9 pages
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