CDC manual confirms 3 month conclusive


Hello Bob, Thank you for your good work.

I found the below CDC manual:

On page 11, they state : "A negative result usually means that the person is not infected with HIV. In rare instances, a person with a negative or inconclusive result may be in the window period. This is the period of time between the onset of infection with HIV and the appearance of detectable antibodies to the virus. The window period lasts for 4 to 6 weeks but occasionally up to 3 months after HIV exposure. Persons at high risk who initially test negative should be retested 3 months after exposure to confirm results."

Do you agree that no matter what the risk is (Having unprotected sex with known HIV+ person) 3 month result is conclusive?

Please clarify & help all.

Thanks, Dev


Hello Dev,

This is always a confusing topic, as folks are always looking for 100% certainty. Unfortunately when it comes to HIV testing, there are many potentially confounding variables, such as:

  1. Different generations of HIV tests as well as different testing assays

  2. Differences in immune response from person to person, which can affect how long it takes to produce detectable levels of specific antibodies

  3. Extenuating circumstances, such as the use of immunosuppressive therapies

Because missing an HIV diagnosis can have catastrophic consequences, organizations that formulate guidelines tend to err on the conservative side. Below is the CDC's most recent comment about testing. As you can see, they continue to mention that in very rare cases it can take up to six months to develop antibodies to HIV. When deciding if three months is definitive or "definitive enough," HIV specialists take into account the likelihood of infection. In your case -- "unprotected sex with a known HIV+ person" -- the CDC would still recommend a six-month test for a conclusive result.

Hope that helps.

Dr. Bob

HIV Testing Basics for Consumers

Should I get tested?

The following are behaviors that increase your chances of getting HIV. If you answer yes to any of them, you should definitely get an HIV test. If you continue with any of these behaviors, you should be tested every year. Talk to a health care provider about an HIV testing schedule that is right for you.

Have you injected drugs or steroids or shared equipment (such as needles, syringes, works) with others? Have you had unprotected vaginal, anal, or oral sex with men who have sex with men, multiple partners, or anonymous partners? Have you exchanged sex for drugs or money? Have you been diagnosed with or treated for hepatitis, tuberculosis (TB), or a sexually transmitted disease (STD), like syphilis? Have you had unprotected sex with someone who could answer yes to any of the above questions? If you have had sex with someone whose history of sex partners and/or drug use is unknown to you or if you or your partner has had many sex partners, then you have more of a chance of being infected with HIV. Both you and your new partner should get tested for HIV, and learn the results, before having sex for the first time.

For women who plan to become pregnant, testing is even more important. If a woman is infected with HIV, medical care and certain drugs given during pregnancy can lower the chance of passing HIV to her baby. All women who are pregnant should be tested during each pregnancy.

How long after a possible exposure should I wait to get tested for HIV?

Most HIV tests are antibody tests that measure the antibodies your body makes against HIV. It can take some time for the immune system to produce enough antibodies for the antibody test to detect, and this time period can vary from person to person. This time period is commonly referred to as the "window period." Most people will develop detectable antibodies within 2 to 8 weeks (the average is 25 days). Even so, there is a chance that some individuals will take longer to develop detectable antibodies. Therefore, if the initial negative HIV test was conducted within the first 3 months after possible exposure, repeat testing should be considered >3 months after the exposure occurred to account for the possibility of a false-negative result. Ninety-seven percent of persons will develop antibodies in the first 3 months following the time of their infection. In very rare cases, it can take up to 6 months to develop antibodies to HIV.

Another type of test is an RNA test, which detects the HIV virus directly. The time between HIV infection and RNA detection is 911 days. These tests, which are more costly and used less often than antibody tests, are used in some parts of the United States.

For information on HIV testing, you can talk to your health care provider or you can find the location of the HIV testing site nearest to you by visiting the National HIV Testing Resources Web site or call CDC-INFO 24 Hours/Day at 1-800-CDC-INFO (232-4636), 1-888-232-6348 (TTY), in English, en Español. Both of these resources are confidential