After a person becomes infected with HIV, the body's immune system recognizes the virus as a foreign intruder and begins to make antibodies to the virus. Antibodies against HIV usually take 1-3 months to develop, rarely longer. Tests to determine if a person is infected with HIV check for the presence of these antibodies. The current HIV antibody blood tests detect antibodies 99% of the time within 3 months of infection.
Testing in most situations involves:
| 1. |
Giving informed consent, which may require signing a form. |
| 2. |
Talking before testing with a test counselor about one's sexual and drug using behaviors, ways to reduce risks for HIV transmission, the meaning of a positive or negative test result, the need for people at risk to learn their HIV serostatus, and any other questions that may come up about HIV. |
| 3. |
Drawing a small amount of blood, or providing an saliva oral or urine sample. |
| 4. |
For regular antibody tests, results are given in about a week either by phone or in person. Rapid testing (in which preliminary results are provided within 30-40 minutes) is becoming increasingly available. |
Positive HIV antibody tests results are over 99% accurate when confirmed. Negative HIV antibody tests are over 99% accurate if it has been at least three months after a contact with exposure to a potentially HIV-infected partner. False negatives or false positives occur very rarely. (For more information on testing see the HIV/AIDS Program Testing Update)
The Window Period
The time period between a person's exposure and actual infection with HIV and until HIV antibodies become detectable in blood or other fluids is called the "window period". Most people will develop antibodies detectable with the latest blood tests within 4-6 1-3 months after infection with HIV. Some people may take longer; but nearly all (>99%) will have antibodies by 3 months following infection. Therefore, we recommend that people wait 3 months from the time of the possible infection with HIV (the date of latest exposure) before being tested for HIV antibodies, and in the meantime assume that they might possible be infected. The test may not give an accurate negative result if a person gets tested too soon after a potential exposure.
People waiting three months from the time of the exposure before testing will have a 99% accurate test result. Very rarely, cases have been reported of people taking longer than three months to develop antibodies to HIV.
