Human Immunodeficiency Virus (HIV) Test

Why It Is Done

A test for the human immunodeficiency virus (HIV) is done to:

• Detect an HIV infection.
• Screen blood, blood products, and organ donors to prevent the spread of HIV.
• Screen pregnant women for HIV infection. Pregnant women who are infected with HIV and receive treatment are less likely to pass the infection on to their babies than are women who do not receive treatment.
• Find out if a baby born to an HIV-positive woman also is infected with HIV. A PCR test is often done in this case because the baby may get antibodies against HIV from the mother and yet not be infected.

The Centers for Disease Control and Prevention (CDC) recommend HIV screening as part of routine blood testing.

The U.S. Preventive Services Task Force (USPSTF) recommends HIV testing:^{footnote 1}

• As part of regular medical care for people 15 to 65 years old.
• For all pregnant women.
• For people younger than 15 and older than 65 if they have a high risk for HIV, such as for people who engage in high-risk behavior.

You and your doctor can decide if testing is right for you.

This test is not done to determine if a person has AIDS. A diagnosis of AIDS means a person is HIV-positive and other problems are present.

How To Prepare

You do not need to do anything before you have this test.

A test for HIV infection can't be done without your consent. Most doctors offer counseling before and after the test to discuss:

• How the test is done, what the results mean, and any other tests that may be done.
• How the diagnosis of an HIV infection may affect your social, emotional, professional, and financial outlooks.
• The benefits of early diagnosis and treatment.

Before the test, it is important to tell your doctor how and where to contact you when your test results are ready. If your doctor has not contacted you within 1 to 2 weeks of your test, call and ask for your results.

How It Is Done

The health professional drawing blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

How It Feels

You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain (or have only minor discomfort) once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your veins, and your sensitivity to pain.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Using corticosteroids.
• Having an antibody test done before a detectable amount of antibodies is present (during the seroconversion period).
• Having an autoimmune disease, leukemia, or syphilis.
• Drinking too much alcohol.

What To Think About

• After initial testing, it is important for your doctor to contact you with the results of your test. Be sure to tell your doctor how and where to contact you. If your doctor has not contacted you within 1 to 2 weeks of your test, call and ask for your results.
• The ELISA is a good screening test, because it is usually positive when an HIV infection is present. But the ELISA test results can indicate HIV is present when it is not (false-positive). So the ELISA alone cannot be used to make a definite diagnosis of HIV infection. No one is considered HIV-positive until he or she has a positive test for HIV DNA or RNA.
• Detecting HIV in a newborn infant is difficult. Until about 18 months of age, even a baby who is not infected may still have HIV antibodies received from his or her HIV-positive mother. A PCR test may be done to see if HIV genetic material (RNA or DNA) is present in the baby.
• To be certain that an HIV infection is not present, a person must test negative for the virus at least 3 months after the last possible exposure to HIV. Testing is often repeated in a few weeks to find out whether a person is infected.
• A screening test for HIV infection may also be done on urine or saliva. An oral HIV test finds antibodies to HIV. Urine testing is rarely done.
• Oral test kits that find HIV-1 and HIV-2 in saliva have been approved by the United States Food and Drug Administration (FDA). The test results are provided the same day. Test results that show an HIV infection need to be confirmed by a PCR test.
• Most states require health professionals, clinics, and hospitals to report confirmed cases of HIV infection to the state health department. Some states allow anonymous reporting (the person's name or other identifying information is not provided). Other states require confidential reporting (identifying information is provided but only to authorized public health officials). All states must report the numbers of cases of AIDS, without names or other identifying information, to the Centers for Disease Control and Prevention (CDC).
• After an HIV infection is present, other tests are done to determine when to treat the infection and how treatment is working. These tests include a CD4+ count and the viral load.
  • CD4+ Count
  • Viral Load Measurement
• Two types of HIV have been identified.
  • HIV-1 causes almost all of the cases of AIDS worldwide.
  • HIV-2 is found mostly in West Africa.