Human immunodeficiency virus, or HIV, is a virus that attacks the immune system. The final stages of HIV are known as acquired immunodeficiency syndrome (AIDS), when the body can no longer fight infections and there is a low t-cell count. There is no cure for HIV or AIDS though patients who discover the virus in early stages can be given therapies that can extend their lives, sometimes by many years. Since early detection is critical and the disease is highly infectious, being tested for HIV is a smart choice.
Blood Tests
The most accurate tests for HIV are made by blood. Blood tests for HIV come in several forms, one of the most common being the enzyme immunoassay or ELISA test. This type of test uses a person's serum, which is diluted and then applied to a plate containing HIV antigens. If HIV is present in the serum, it will bind with the antigens. The plate is then washed, and a secondary antibody which is chemically linked to an enzyme is applied, then washed again. A substrate for the enzyme is then applied, causing a change in color, and allowing the technician to read the results of the test. Given the nature of this type of test, results take several days to compute, but are very accurate.
Oral Tests
Oral tests use oral fluid to detect the presence of HIV antibodies. This is done in much the same manner as the ELISA test. If a is obtained during the testing procedure, the oral test is then followed up with a Western blot test using the same oral fluid sample. A positive result on both test is needed for a confirmed diagnosis. This type of oral test, like a blood test, can take several days to obtain results from, particularly if a Western blot test is required.
Rapid Tests
Rapid testing is a recent development in testing procedures for HIV. Unlike ELISA tests, rapid test results can be read in about 20 minutes. There are several varieties of rapid test approved for use in the U.S. The rapid test can use either blood or oral fluid. According to the CDC, the rapid tests have roughly the same accuracy as an ELISA test, but as with other tests they must be followed up with secondary testing to confirm a positive diagnosis.
RNA Tests
RNA tests are used for early diagnosis of HIV, where antibodies to the disease may not yet be present. This type of test looks for the nucleic acid of HIV itself in the blood sample. Nucleic acid is present long before the antibodies can be produced, and it is for this reason that this test is used for early detection. A positive test result on an RNA test must also be followed up by secondary testing in order to confirm a positive diagnosis.
Home Tests
Home testing is also a relatively recent development in testing procedures for HIV. This allows patients to collect a blood sample themselves and send it to a lab for analysis. Currently, only one home collection kit is approved for use by the FDA: the Home Access HIV-1 Test System. This kit provides a sterile tool for pricking the finger to collect a blood sample, which is then placed on a specially treated card and sent to the lab. When results are ready, the patient may phone the lab. Patients are assigned a code number so results are anonymous. A positive result on a home collection test also needs to be followed up by additional testing performed by a medical professional.
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