Backgrounder: Donor Testing - Human Immunodeficiency Virus (HIV)
Nucleic Acid Testing (NAT) is a highly sensitive method of testing blood that is used to detect Human Immunodeficiency Virus (HIV-1) as well as Hepatitis C virus (HCV), Hepatitis B virus (HBV) and West Nile Virus (WNV) in blood.
Introduced in 2001 for HIV, NAT greatly reduces the length of time HIV can go undetected in a person infected with the virus. However, there is still a window period (approximately 9 day) period shortly after infection when an individual may transmit HIV but the virus is not detected by our tests.
In addition to testing every donation, we rely on our donors to be honest about their exposure risks when completing the donor eligibility screening criteria, which is part of a multi-tiered safety system designed to protect patients.
The window period is the time shortly after a donor has become infected with HIV but antibody cannot yet be detected by a blood test.
There are approximately one to eight HIV positive donations a year, with close to 1 million donations tested. However, these are detected and removed from the supply. There have been no cases of transfusion-transmitted HIV in Canada since implementation of testing in 1985.
The residual risk for HIV is estimated at less than 1 in 8 million units at Canadian Blood Services.
During the donation process, about 450 mL is collected for transfusion and a small amount of blood is kept for testing at one of Canadian Blood Services’ two testing sites.
In 2014, Canadian Blood Services collected and distributed about approximately 850,000 units of blood and blood products to all territories and provinces except the province of Québec, which is managed by Héma-Québec.
Donor Testing: human immunodeficiency virus (HIV)
Canadian Blood Services takes responsibility for the safety of the blood supply. Canadian patients depend on us to manage a safe, secure and cost-effective blood system. Emerging risks and best practices are monitored continuously to make sure that our blood and blood products are safe and of highest quality. Ensuring the safety of both donors and recipients is paramount at Canadian Blood Services and that is why we test every donation for a range of infectious diseases that may be transmitted by blood transfusion, including Human Immunodeficiency Virus (HIV).
Why it is important
Before the introduction of testing for HIV in the mid-1980s, thousands of Canadians were infected through tainted blood products. The Canadian Red Cross Society (responsible for Canada’s blood supply at that time) introduced a donor eligibility screening criterion that excluded all men who have had sex with a man even once since 1977, as was also done in the USA. This criterion was embedded into Health Canada regulations in 1992. In 2013, the criterion was reduced to a five-year deferral period for men who have sex with men. Consultations are currently underway to consider a further reduction to a one-year deferral.
Today, through a multi-tiered approach to safety that includes donor education, strict adherence to the donor screening criteria and the testing of all donated blood, Canadian Blood Services ensures that Canadian patients are not put at increased risk for infectious diseases that may be transmitted by blood transfusion, including HIV.
How it works
We use antibody testing and nucleic acid testing (NAT) to test every donation for HIV. While our state-of-the-art technology is sophisticated, there is a brief period shortly after infection when HIV is not detectable in a donor. If an individual were to donate blood during this ‘window period’ in the early stages of infection, our testing process would not detect the virus and that donation would be infectious to a patient.
During the blood donation process, about 450 ml is collected for transfusion and a small amount of blood is kept for testing at one of our two testing sites.
In the testing laboratory, NAT testing begins with six blood samples being 'pooled' together. If the result of a pool of samples is negative, all samples in the pool are negative. If the pool is positive, then the samples are tested individually until the actual positive sample is identified.
If a sample is identified as positive, additional confirmatory testing is performed and Canadian Blood Services will notify the donor, provide further information to the donor and their physician if required, and discard all the products made from that donation.