NAT is a gene-based method that can detect very small amounts of genetic material. It can detect HIV-1 earlier than antibody or antigen test methods. Because of the high-sensitivity of this method, NAT testing is used to screen donated blood, plasma, and tissue products.
A qualitatitive NAT method may also be the preferred method in the following situations:
- When the anti-HIV screening test is negative and the patient is at increased risk for HIV infection
- When the western blot test result is indeterminate
- If the patient has participated in an HIV vaccine study and, as a result, may have developed antibodies to HIV
- To diagnose infection in newborns born to HIV-positive mothers, as maternal antibodies would interfere with regular screening methods.
Quantitative NAT methods (also known as viral load assays) are used for patient monitoring after a diagnosis of HIV infection has been made.
The primary target of HIV NAT testing is viral RNA in plasma. An amplification step is employed, either target amplification or signal amplification, to increase levels of nucleic acids to detectable levels.