Window periods are based on averages and/or statistics from studies. There are a few different types of HIV tests and these tests have different window periods.
For more information about HIV window periods, click here.
For most people in BC, testing for HIV will involve either an antibody or a combined antigen and antibody test. Here is a brief explanation of these tests:
- Antibody tests: These tests measure antibodies to HIV. It takes time after someone has been exposed to HIV for the body to make these antibodies. This type of test is used when tested using a point-of-care (POC, rapid) test.
The window period for this test is 3 weeks to 3 months. Up to 95% of people will have antibodies by 6 weeks, and 99% after 3 months.
- Antigen tests: antigens viral proteins; the antigen used to detect HIV is called p24 antigen. P24 antigen shows up in the blood soon after a person gets HIV.
The 4th Enzyme Immunoassay Test (EIA) is a combined antigen/antibody test and is the standard HIV laboratory blood test used in BC.
The window period is 6 weeks (when 99% of people would test positive, if they got HIV).
- Nucleic acid amplification test (NAAT): looks for genetic material of HIV in the blood. It is sometimes referred to as an “early HIV test” or “RNA test”. This test is only used by doctors or nurses under specific circumstances, such as a recent high-risk exposure to HIV and/or they are having HIV-related symptoms.
The window period is 10-12 days (when 90% of people would tests positive, if they got HIV) to 6 weeks (when 99% of people would test positive, if they got HIV).
There is a tool you can use to calculate HIV window periods, click here to learn more.