Nucleic Acid Amplification Testing (NAT) for Hepatitis C
Frequently Asked Questions
1. What is Nucleic Acid Amplification Testing?
Nucleic Acid Amplification Testing (NAT) is a highly-sensitive method of testing blood that is used to detect Hepatitis C virus (HCV), Human Immunodeficiency Virus (HIV-1) and West Nile Virus (WNV) in blood.
Most traditional screening tests require the presence of antibodies to trigger a positive test reaction. The period of time between initial infection and detection of antibodies is called the "window period". NAT reduces the window period by detecting low levels of viral genetic materials that are present soon after infection but before the body has had a chance to start producing antibodies.
2. Why did Canadian Blood Services implement NAT?
NAT has been implemented for the following reasons:
NAT testing provides Canadians with a safer blood supply by detecting low levels of viral genetic material present when an infection occurs but before the body begins producing antibodies in response to a virus. Because of this, NAT reduces the 'window period' or the time between initial infection and when the virus is first detectable using current antibody tests.
NAT is becoming the standard of practice in the blood and plasma industry in the United States and elsewhere in the world. Other countries are also moving toward its introduction and it is crucial that Canada keeps on par with international safety standards. Blood products cross international borders so it is important to have consistent standards.
3. How does NAT work?
NAT testing begins with a number of blood samples being 'pooled' together in the laboratory. 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 in smaller pools and then individually until the actual positive sample is identified. When a sample is identified as positive, Canadian Blood Services will notify the donor, provide appropriate counselling to that individual, and discard all the products made from that donation.
4. Isn't this an expensive process to undertake for a fairly minimal benefit?
In the past couple of decades, major progress has been made in testing blood for transmissible diseases. Because of this progress, future testing is likely to add incremental benefit. By detecting cases of Hepatitis C, HIV-1 and West Nile Virus, we are helping protect Canadians from often debilitating and sometimes fatal diseases. Canadian Blood Services is committed to fulfilling the principles of the Krever Report, which puts safety first.
We must also move in tandem with the rest of the world. The United States has already introduced NAT and other countries are moving towards its introduction.
5. Can NAT replace the previous antibody tests?
NAT is used in addition to antibody tests. Some individuals infected with Hepatitis C or HIV may be NAT-negative if the amount of virus present has fallen below detectable levels. In such cases antibodies to the virus would still be detected by current tests for hepatitis C or HIV-1.