Anti-HIV 1-2 (HIV Test)
Definition
There are three main types of test, and each has a different detection window:
| Test type | What it detects | When it detects infection after exposure |
|---|---|---|
| Antibody test | HIV antibodies in blood, saliva or urine | 23 to 90 days |
| Antibody/antigen combo | Both antibodies and antigen, the most widely used | Laboratory: 18 to 45 days · Rapid test: 18 to 90 days |
| NAT (nucleic acid test) | Detects the virus directly | 10 to 33 days, the earliest. Because of its cost it is used for treatment monitoring rather than routine screening |
Purpose
Everyone between the ages of 13 and 64 is advised to have an HIV test at least once. People with risk factors (unprotected sex with an HIV-positive partner, sharing needles, a recent STI diagnosis) need additional testing. Pregnant women may be tested to prevent transmission.
Results
- Negative, HIV was not detected; however, if you are within the window period you may still be infected, and repeat testing is needed
- Positive, a confirmatory test is required (except for NAT). Once a positive diagnosis is confirmed, antiretroviral treatment is started immediately
Risks and Limitations
The window period is the most critical concept:
No test can find HIV immediately after exposure; it can take weeks for the signs of HIV in your body to rise enough to show up on a test.
In other words, a negative test taken immediately after a risky exposure provides no reassurance. The timing of repeat testing should be set according to which test was performed.