If you're worried that you might have been exposed to human immunodeficiency virus (HIV) -- the virus that causes AIDS -- it's important to get tested as soon as possible. Although the prospect of being diagnosed with the disease can be scary, today you can live a long and full life with HIV, especially if you start treatment early. Knowing you are infected can also help you take precautions so that you don't pass the virus to other people.
Several different tests are used to diagnose HIV infection. Other tests are used to select and monitor treatments in people who are living with HIV. This article covers both types of HIV tests.
CD4 cells are a type of white blood cell that fights infection. Another name for them is T-helper cells. CD4 cells are made in the spleen, lymph nodes, and thymus gland, which are part of the lymph or infection-fighting system. CD4 cells move throughout your body, helping to identify and destroy germs such as bacteria and viruses.
The CD4 count measures the number of CD4 cells in a sample of your blood drawn by a needle from a vein in your arm. Along with other tests, the CD4 count helps tell how...
You are at risk for HIV infection and should be tested for it if:
You’ve had several sexual partners.
You had unprotected sex with someone who is or could be HIV-positive.
You have used injected drugs or steroids or shared needles or other equipment during drug use.
You have had any sexually transmitted disease, including herpes, hepatitis, or TB.
You have had sex for drugs or money.
You’ve had sex with someone who has a history of any of the above -- or with someone whose sexual history you don’t know.
There are several types of tests that screen blood (and sometimes saliva) to see if you are infected with HIV.
Newer tests can detect the presence of HIV antigen, a protein, up to 20 days earlier than standard tests. This helps prevent spread of the virus to others and means an earlier start for treatment. It is done with a pinprick to the finger.
Here's a look at available HIV tests:
Standard tests. These blood tests check for HIV antibodies. Your body makes antibodies in response to the HIV infection. These tests can't detect HIV in the blood soon after infection because it takes time for your body to make these antibodies. It generally takes two to 8 weeks for your body to produce antibodies, but in some cases it can take up to six months.
In standard tests, a small sample of your blood is drawn and sent to a lab for testing. Some of the standard tests use urine or fluids that are collected from the mouth to screen for antibodies.
Rapid antibody tests. Most of these are blood tests for HIV antibodies. Some can detect antibodies in saliva. Results are available in under 30 minutes and are as accurate as standard tests.
Antibody/antigen tests. These tests are recommended by the CDC and can detect HIV up to 20 days earlier than standard tests. They check for HIV antigen, a part of the virus that shows up 2-4 weeks after infection. These tests can also detect HIV antibodies. A positive result for the antigen allows treatment to begin earlier and the patient to avoid infecting others. These are blood tests only.