How long does an HIV test take?

Dear Wondering,

Waiting for test results can certainly be stressful — and while the past few decades of research on human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) have made great advances in testing technology, it's tough to give an exact estimate of how long it takes to get test results. There are many factors to consider, including: the type of HIV test completed, how long it takes for a particular community health center or lab to analyze and report the test result to the patient, and how long someone has waited to get tested after an exposure (more on that later). Also, sometimes the results must go through a health care provider first, who will then relay them to the patient, which can take more time. The good news is that many testing options are fairly quick. While the most rigorous lab-based tests can take several days to produce a result, some rapid tests can take as little as 20 minutes.

In general, the turn around time for HIV testing depends on the type of testing performed. These tests include:

• Antibody self-tests look for antibodies by collecting fluid from a person’s mouth using an oral-swab. This self-test, which is currently the only approved at-home HIV test, only accepts an oral-fluid sample and typically returns results within 20 minutes.
• Rapid antibody/antigen testing usually requires blood from a finger prick or saliva (i.e., from an oral swab). Not only does this test check for antibodies, but it looks an antigen known as p24 as well. For individuals with HIV, this antigen can be produced prior to the development of antibodies. Typically, for this kind of testing, results are ready within 30 minutes of testing.
• Laboratory-based tests use methods that are more accurate, but may also take several days to return results. There are two kinds of laboratory-based tests that can be done: an antigen/antibody test and a nucleic acid test (NAT). A laboratory-based antigen/antibody test usually requires blood to be drawn from your vein and then sent off to a lab where it is determined whether the blood contains HIV or not. A NAT tests uses a blood sample to see whether HIV is present in the person's blood or not. However, this test is particularly expensive and isn’t recommended unless there was an incident of possible or high-risk exposure or the individual is experiencing early symptoms of HIV.

Keep in mind that no matter what method is used, it’s recommended that people wait a certain period of time after exposure before testing can even be started. Why, you ask? After exposure to the HIV virus, the body needs to produce a sufficient level of antibodies in order to be detected by any test. Antibodies are the proteins that develop in the body in response to a particular infection to attempt to fight it off. According to the Centers for Disease Control and Prevention (CDC), the timeframe from when a test can accurately tell if you have HIV or not is different for everyone and differs between each test. In general, the window period for each test is the following:

• NAT: 10 to 33 days after exposure
• Laboratory antigen/antibody test: 18 to 45 days after exposure
• Rapid antigen/antibody test and antibody self-test: 18 to 90 days after exposure

What if the results are inconclusive? Unfortunately, this happens and means that it's unclear if the results were positive or negative. In that case, getting tested again as soon as possible is recommended. A re-test may be done on the same sample as before or a new sample may need to be collected, depending on the situation. Because of this, additional testing may mean that it could take even more time before a clear result is produced. However, it can give peace of mind regarding the accuracy of the results. Finally, it might help to be aware that re-testing is usually not recommended for people who are on anti-retroviral therapy (ART), as the chances of receiving a false-negative result is relatively high.

In the meantime, if you think you've been exposed to HIV, have not been able to get tested yet, and are sexually active, it’s recommended that you practice safer sex (oral, vaginal, or anal) during the time you or your partner(s) are waiting for testing to begin, as well as while you're waiting for the results. Safer sex, such as using a condom (internal or external) and dental dams, reduces the risk of potential exposure to your partner(s) while you wait and minimizes the risk of additional exposure for yourself. Additionally, injection drug use can also be a risk behavior that transmits HIV, so if your participate in this, it would be wise to ensure that needles aren't being shared. 

Still have questions regarding HIV testing? To learn more, you could check out the HIV/AIDS category in the Go Ask Alice! Sexual & Reproductive Health archives. To address any concerns that relate specifically to you, it may be helpful talk with your health care provider or a professional at your local sexual health clinic. They can help you make decisions that are most appropriate for your overall health and lifestyle. You might also want to check out the CDC National HIV, STD and Hepatitis Testing for more information!

Here’s hoping you didn’t have to wait long to get results (answers) from this response!