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Testing and Diagnosis

Of the estimated 1.1 million Americans currently living with HIV, 21 percent do not know they are infected. People who have been infected recently with HIV often have few to no symptoms yet are extremely infectious and may unknowingly transmit the virus to others. Therefore, the Centers for Disease Control and Prevention (CDC) recommends HIV testing for adults, adolescents, and pregnant women during routine medical care.1 Regular HIV screenings allow healthcare providers to identify people who are not aware that they are infected with HIV, so that they can be counseled on the need to avoid high-risk behaviors, instructed on safe-sex practices, and given information about starting antiretroviral therapy. HIV testing can also be performed anonymously if a person is concerned about confidentiality.

When should I get tested for HIV?

You should be tested at least once to find out your HIV status. Ask your doctor or nurse if and when you need the test again. All pregnant women should be tested for HIV. All other women should be tested at least once to find out your HIV status. You should be tested more often if you are at higher risk of HIV infection. You are at higher risk if you:

  • Having unprotected sex with more than one partner
  • Injecting drugs, either now or in the past
  • Having sex with someone to get money or drugs in return, or having sex with someone who has traded sex for money or drugs
  • Having sex, now or in the past, with someone who has HIV, is bisexual, or injects drugs
  • Having another sexually transmitted infection (STI)
  • If you had a blood transfusion between 1978 and 1985

Remember, these are not the only ways to get HIV, and are not the only reasons to get tested. All people should know their HIV status. But many do not. About one in five people infected with HIV or AIDS in the United States do not know they have it. Many new HIV infections are caused by people unaware that they are infected. It can take between two weeks and three months after infection for HIV antibodies to be found in your blood. So, it may take up to three months for an HIV test to be positive if you were very recently infected.

It is important to know your HIV status for these reasons:

  • Many new HIV infections are caused by people unaware that they are infected.
  • HIV medicines are more effective if you start them early.
  • Starting treatment early can mean the best health for you and a longer time before you develop AIDS or other infections. Unfortunately, most people do not find out they have HIV until the disease is at advanced stages. This limits the treatment options.

There is good news. Though many Americans still don't know they have HIV, more people are getting tested than ever before. If you don't know your status, it's time to find out. Testing is quick and easy, and there are many places to get tested: HIV testing centers, health departments, hospitals, private doctors' offices, and clinics. To get tested:

If you test negative, you can take steps to stay that way. If you find out that you are infected with HIV, treatment can slow down the progress of the virus. If you are pregnant, you also will be able to help prevent passing HIV to your baby. You can tell your sex partners if you have HIV and protect them from getting the virus.

Types of HIV tests

Antibody tests are often used to screen for HIV. Antibodies are things that the body makes to try to fight infections, such as HIV. Antibody tests look for antibodies to HIV, rather than the HIV itself. Antibodies to HIV often can be found between two weeks and three months after infection. Depending on the test and the place where you are tested, results come back within a few minutes to a few weeks. Ask your doctor or testing center how long you must wait.

These are some kinds of antibody tests:

  • Enzyme immunoassay (EIA) tests. These tests are the most common and give results in a day to one to two weeks.
  • Rapid tests. These are antibody tests that give you results quickly, usually in about 20 minutes. Rapid tests use blood from a vein or a finger stick or fluid from your mouth to look for antibodies to HIV. If you are HIV-negative, these are just as accurate as the EIA test. If you test HIV-positive with this test, you will need a follow-up blood test to confirm the results.
  • Home Access Test. With this antibody test, you take your blood sample at home and mail it to a lab for testing. Results are provided over the phone by a counselor. You do not have to give your name. You will receive an ID number to use when you call for the results. There is only one home test approved by the U.S. Food and Drug Administration (FDA): Home Access HIV-1 Test System . It takes about seven days to get test results. Home Access also makes an express test with results available the day the lab receives your shipment. It takes three to seven days to get test results. You can buy this FDA-approved test online or at the drugstore. Beware: Online you can buy several HIV home test kits that are not approved by the FDA. Many of these tests give wrong results.

If you test positive with an antibody screening test, you will need a second type of test to confirm that you are infected. You must wait a few days to a few weeks for the results.

DNA and RNA tests look for parts of the HIV itself. These tests are not used as often as the antibody tests. But they are useful in some specific cases, such as testing for HIV in a newborn baby whose mother is HIV-positive and testing someone who has just become infected (who has acute HIV infection).

HIV Testing in Infants

CDC recommends that all pregnant women get tested for HIV before and/or during delivery. Knowing the HIV status of the mother allows physicians to prevent mother-to-child HIV transmission by providing antiretroviral treatment to both mothers infected with HIV and their newborn infants. However, it is difficult to determine if a baby born to a mother infected with HIV is actually infected because babies carry their mothers’ HIV antibodies for several months. Today, healthcare providers can conduct an HIV test for infants between ages 3 months and 15 months. Researchers are now evaluating several blood tests to determine which ones are suitable for testing babies younger than 3 months.

Diagnosing AIDS

With the right treatments, HIV-positive people can live for decades before developing AIDS. How can you tell when HIV has progressed to AIDS? You can't. AIDS is not a diagnosis you can make yourself. Only your doctor can do that. You have developed AIDS if you are infected with HIV and:

  • Your CD4+ count drops below 200 cells per cubic millimeter. (Healthy adults have CD4 counts of 1,000 or more.)
  • You have an AIDS-defining condition, which is an illness that is very unusual in someone not infected with HIV. You can read about some of these conditions in the section on opportunistic infections (OIs).

There are some things that may make it more likely that you will progress to AIDS sooner. For instance, people who have symptoms when they are first infected with HIV tend to get AIDS sooner than people who have no symptoms. There are different kinds (strains) of HIV, and each one of those may progress at a different rate. Infection with more than one strain of HIV can also lead to AIDS or other infections more quickly.

AIDS isn't the only reason that you need to keep up-to-date with visits to your HIV doctor. Today, about half of the people who die from HIV-related infections are getting infections other than AIDS. You need to keep track of your CD4 count and ward off OIs to stay healthy. The Centers for Disease Control and Prevention recommends that HIV-positive women who don't have any symptoms have screenings every year. Some women may need screenings more often, so ask your doctor what is right for you.

  • See where to Get an HIV test.

  • References

    1Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings,CDC September 2006.

    Information published courtesy of NIAID & Womens Health.

    This article was last modified in: 06/18/2012