HIV/AIDS |
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Tests for HIV and AIDS
Blood tests are the most common way to diagnose the human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS). These tests look for antibodies to the virus that are present in the blood of infected individuals. People exposed to the virus should get tested immediately.
Early testing is crucial with HIV. If you test positive for the virus, you and your doctor can develop a treatment plan to help fight HIV and ward off complications. Early testing also can alert you to avoid high-risk behavior that could spread the virus to others.
Because it can take from six weeks to a year to develop antibodies to the virus, follow-up tests may be needed. Your doctor will ask about your symptoms, medical history and risk factors and perform a physical examination.
The primary tests for diagnosing HIV and AIDs include:
ELISA Test — ELISA, which stands for enzyme-linked immunosorbent assay, is used to detect HIV infection. If an ELISA test is positive, the Western blot test is usually administered to confirm the diagnosis. If an ELISA test is negative, but you think you may have HIV, you should be tested again in one to three months. ELISA is quite sensitive in chronic HIV infection, but because antibodies aren't produced immediately upon infection, you may test negative during a "window" of a few weeks to a few months after being infected. Even though your test result may be negative during this window, you may have a high level of the virus and be at risk of transmitting infection.
Home Tests — The only home test approved by the U.S. Food and Drug Administration is called the Home Access Express Test, which is sold in pharmacies.
Saliva Tests — A cotton pad is used to obtain saliva from the inside of your cheek. The pad is placed in a vial and submitted to a laboratory for testing. Results are available in three days. Positive results should be confirmed with a blood test.
Viral Load Test — This test measures the amount of HIV in your blood. Generally, it's used to monitor treatment progress or detect early HIV infection. Three technologies measure HIV viral load in the blood — reverse transcription polymerase chain reaction (RT-PCR), branched DNA (bDNA) and nucleic acid sequence-based amplification assay (NASBA). The basic principles of these tests are similar. HIV is detected using DNA sequences that bind specifically to those in the virus. It is important to note that results may vary between tests.
Western Blot — This is a very sensitive blood test used to confirm a positive ELISA test result.
Other Tests
If you're infected with HIV, additional blood tests may be ordered to check for other infections. Tests may be administered to check the effects of medications on your liver and kidneys and other organs. Other common tests include:
CD4+T Cell Count — As soon as HIV enters the body, it begins to destroy or disable your bodys CD4+T cells, the immune system's key infection fighters. The CD4+T cell count is a blood test that measures the number of CD4+T cells and helps assess the immune system's health. The CD4+T cell count correlates with a person's risk of developing opportunistic infections and is a useful marker for HIV disease staging and treatment planning. The Center for Disease Control and Prevention (CDC) recommends CD4+T testing every three to six months in all HIV-infected patients, though the need may vary by individual. HIV Resistance Testing — Resistance to anti-retroviral drugs is fairly common in some HIV-positive patients. Resistance testing can be useful to determine the drugs not to use in a patient with increasing levels of the virus despite therapy or in a previously untreated individual who may have been infected with a virus that is resistant to one or more of the HIV drugs.
More Information:
Reviewed by health care specialists at UCSF Medical Center.
Last updated May 8, 2007
This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.
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