The immune system begins to produce antibodies in an attempt to fight the HIV virus as soon as the virus enters the body. HIV/AIDS tests screens for and diagnoses an infection by either detecting the antibodies, or by testing virus levels in the body. Understanding the AIDS test can allow for early HIV diagnosis and treatment, which can improve long-term health. HIV status awareness can also lead to behavior modification that may help prevent the spread of HIV and AIDS to others.
HIV Antibody Tests
The several types of HIV antibody tests usually require a two-step process. The enzyme immune assay, also called an EIA, or the enzyme-linked immunosorbent assay, or ELISA, works quickly by testing blood, oral fluids or urine to detect HIV antibodies within as little as 20 minutes. These tests are highly accurate, according to the New York University Medical Center HIV Infosource website. If the EIA/ELISA test is negative, testing is complete. A secondary and more specific "Western Blot" test is necessary to confirm a positive EIA or ELISA test result. According to the Centers for Disease Control and Prevention, blood tests are the most accurate.
Home testing kits allow for blood collection at home using a finger prick. Users simply return the sample by mail and call in for test results.
RNA Tests
RNA tests detect the amount of "virus load" or virus material in the blood. Doctors will order an RNA test on the rare occasion when antibody tests fail to detect HIV antibodies. According to the Seattle and King County Public Health website, RNA tests are more complex for the lab to process, are more expensive, and take longer to get results.
Understanding Test Results
If the EIA/ELISA test is negative, then testing is complete. A secondary and more specific "Western Blot" test is necessary to confirm a positive EIA or ELISA test result.
A negative result means it is likely there is no HIV infection. That said, there is a three- to six-month window during which those recently infected with HIV are developing antibodies. According to the Infosource website, the existence of this window period underscores the importance of regular HIV testing for high-risk individuals.
A retest is necessary when test results are inconclusive or indeterminate, in order to rule out the possibility of test error. If the second test also comes back inconclusive, then an RNA or viral load test is usually ordered.
When to Get Tested
The CDC outlines several behaviors considered "high risk" that will greatly increase the chances of HIV transmission. These include unprotected vaginal, anal or oral sex, particularly with multiple or anonymous partners; intravenous drug use that involves shared equipment like needles or syringes; and the diagnosis of a sexually transmitted disease, tuberculosis or hepatitis.
The American Association for Clinical Chemistry website Lab Tests Online further defines multiple partners as three or more during the last 12 months, and recommends testing for those uncertain about a sexual partner's risk behaviors. Testing is also important for any pregnant woman or woman who is thinking of becoming pregnant, and for health care workers whose jobs involve direct exposure to blood.
When to Retest
The CDC states that three to six months is the average window period during which a person with HIV virus is developing antibodies. For that reason, the CDC recommends retesting three months after exposure, and again six months after exposure. Detection takes between nine and 11 days with RNA or viral load tests.
