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To screen for and diagnose human immunodeficiency virus (HIV) infections
A blood sample collected from a vein or by pricking the tip of a finger (fingerstick) or saliva (oral fluid), which may be collected by swabbing your gums.
Human immunodeficiency virus (HIV) is the virus that can cause acquired immunodeficiency syndrome (AIDS). HIV screening tests detect the HIV antigen (p24, a viral protein) and/or HIV antibodies produced by the body in response to an HIV infection in the blood. Some tests detect HIV antibodies in saliva.
An HIV infection may initially cause no symptoms or cause flu-like symptoms that resolve after a week or two. The only way to determine whether you have been infected is through HIV testing.
If left untreated, an HIV infection can progressively destroy the body's ability to fight infections and certain cancers. HIV weakens the immune system by infecting lymphocytes (T-cells), a type of white blood cell, that normally help the body fight infections.
During the first few weeks following infection with HIV, the virus infects T-cells, making numerous copies of itself and continuing to infect more T-cells. The amount of virus (viral load) and the p24 antigen level in blood can be quite high. HIV tests that detect the p24 antigen can generally identify infections in the first weeks after infection, even before antibodies develop.
About 2-8 weeks after exposure to the virus, the immune system responds by producing antibodies directed against the virus that can be detected in the blood. As the initial infection resolves and the level of HIV antibody increases, both virus and p24 antigen levels decrease in the blood. HIV tests that detect HIV antibodies can identify HIV infections about 2 to 8 weeks after infection.
If you become infected with HIV and it is not detected early and treated, it may become a simmering infection that may cause few symptoms for a decade or more. If your infection is still not treated, eventually symptoms of AIDS emerge and begin to progressively worsen. Over time and without treatment, HIV destroys the immune system and leaves your body vulnerable to other debilitating infections.
For additional details on HIV signs and symptoms, risks, treatment, etc., see the article on HIV Infection and AIDS.
Detecting and diagnosing HIV early in the course of infection is important because:
There are two types of HIV, called HIV-1 and HIV-2. HIV-1 is the most common type found in the United States, while HIV-2 has a higher prevalence in parts of Africa.
HIV tests are used to screen for and diagnose HIV infections.
Different types of tests may be used for HIV screening:
If any one of the above screening tests is positive, then it must be followed by a second test to confirm the diagnosis. This second test is an antibody test that is different than the first test. If the second test does not agree with the first test, then a third test is performed that detects the genetic material (RNA) of the virus. An HIV RNA test will detect HIV in most people by 1-4 weeks of infection.
Several organizations recommend routine screening for HIV:
For additional details on screening recommendations, see the articles for Teens, Young Adults, Adults, and Adults 50 and Up.
Annual screening is advised for those who are at high risk for HIV and is recommended when you:
You should get at least a one-time test, regardless of age, if you:
Also, a negative screening test means only that there is no evidence of disease at the time of the test. If you are at increased risk of HIV infection, it is important to have screening tests performed on a yearly basis to check for possible exposure to the virus.
The CDC recommends the following testing protocol to screen for and diagnose HIV infection:
There are a few different ways you can get access to HIV screening:
The home test has two limitations:1. The saliva test is less sensitive than a blood test, so the home test may miss some cases of HIV that a blood test would detect.
It depends on the test. Combination tests that use a blood sample drawn from a vein and detect HIV antigen (p24) and HIV antibodies can detect HIV infections in most people 2 to 6 weeks after infection. Combination tests that use fingerstick blood samples detect HIV infections about 2 to 12 weeks after infection. Blood tests that detect HIV antibody alone can detect infections in most people about 3 to 12 weeks after infection.
Yes. If you test positive for HIV infection, it is important that you tell your healthcare practitioners as well as all current and future sex partners and/or anyone with whom you share needles. Counseling services are often available from the clinic that performed the test or from your healthcare provider that will help you to inform the people who need to know.
Your HIV status, like other medical conditions and test results, is protected by the HIPAA Privacy Rule and cannot be shared with friends, family, or employers without your written permission. Your HIV status may be shared with your healthcare providers who have a "need to know" in order to treat you. Also, in order to determine the incidence of HIV and to provide appropriate prevention and care services, all new cases of HIV are reported to state and local health departments.
Certain testing centers provide either anonymous (your name is never given) or confidential (your name is given but kept private) HIV testing and counseling. You can also contact your state or local health department to find out where testing may be available.
If you are HIV-positive, follow-up tests may include the following:
There is currently no vaccine to protect you against HIV, but avoiding high-risk activities such as having unprotected sex and sharing needles for injecting drugs can help to prevent its spread.
While there is no vaccine, the CDC and the World Health Organization recommend that individuals without HIV infection but at high risk for it consider taking pre-exposure prophylaxis (PrEP), a daily pill to help prevent infection. For people taking PrEP consistently, the risk of HIV infection was significantly lower (up to 92%) compared to those who didn't take it.
If you have HIV, early diagnosis of your infection is important to prevent its transmission to others and to allow evaluation, monitoring, and treatment. Healthcare workers can protect themselves from HIV infection by following universal precautions, such as wearing gloves and avoiding needle sticks.
Post-exposure prophylaxis (PEP) is another strategy for preventing HIV. PEP is taking antiretroviral medication after recent possible exposure to the virus. PEP should only be used in emergency situations and must be taken within 72 hours of possible HIV exposure. Talk to your healthcare practitioner or emergency department doctor about PEP right away if you:
If you are pregnant, it is important to determine if you have HIV so you can be treated. Treatment of HIV-infected mothers during pregnancy, precautions at birth, and avoiding breast-feeding can minimize the risk of passing the infection from mother to child. If you are already taking HIV medications when you become pregnant, you should continue to do so during pregnancy and labor and delivery. If you are not taking HIV medications or have a high viral load during pregnancy, giving the antiretroviral drug zidovudine intravenously during labor and delivery and also to the newborn twice a day by mouth for 6 weeks reduces the rate of transmission from 25-33% to about 1-2%.
No. Because maternal antibodies are transferred from mother to baby and stay in the newborn's system for 6 to 18 months, a different test must be used. A test that detects the genetic material, either an HIV RNA or HIV DNA test, is required.
Symptoms of the initial HIV infection can mimic those of influenza and other viral infections. The only reliable way to tell if you are infected is to get tested. Many people with HIV do not experience symptoms for years after the initial infection or have symptoms that are very similar to symptoms of other illnesses. For more, see this CDC web page: About HIV.
Currently, there is no cure for HIV infection or AIDS. However, early diagnosis allows for treatment with antiretroviral therapy (ART) that can help to suppress levels of virus in your body (viral load) and greatly improve your long-term health. The U.S. Department of Health and Human Services (DHHS) as well as the World Health Organization recommend that all individuals diagnosed with HIV infection receive treatment as soon as possible, including pregnant women. With advances in treatment, individuals with HIV infection are living longer, healthier lives.
People typically take at least three drugs from two different classes in order to prevent or minimize virus replication and the emergence of drug-resistant strains. Combinations of three or more antiretroviral drugs are referred to as highly active antiretroviral therapy or HAART. Read the Treatment section of the article on HIV Infection and AIDS for additional details.
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