Infection with HIV has no specific symptoms. The only way you can find out for sure if you are infected with HIV is by taking the HIV antibody test.
The HIV antibody test looks for antibodies to the virus in a person's blood. For most people these antibodies take 3 months to develop. In rare cases, it can take up to 6 months. It would be extremely uncommon to take longer then 6 months to develop detectable antibodies.
Getting tested before the 3 month period is up may result in an unclear test result, as an infected person may not have developed antibodies to HIV yet. So it is best to wait for at least three months after the last time you were at risk before taking the test. Some test centres may recommend testing again at 6 months, just to be extra sure.
It is also important that you are not at risk of further exposures to HIV during this time period. Most importantly you should continue to practice safe sex and not share needles.
The vast majority of HIV tests are antibody tests. Other tests are available that can be used in specific circumstances, such as the p24 antigen test and the PCR test.
Who should take the test?
Testing ofr HIV is highly recommended, if:
You think you may have been exposed to the HIV.
You are sexually active (3 or more sexual partners in the last 12 months)
You have a sexually transmitted disease (STD), including pelvic inflammatory disease (PID).
You are a health care worker with direct exposure to blood on the job.
You are pregnant. There are now treatments that can greatly reduce the risk that a pregnant woman who has HIV will give the virus to her baby.
You are a woman who wants to make sure you are not infected with HIV before getting pregnant.
You received a blood transfusion between 1977 and 1985, or a sexual partner received a transfusion and later tested positive for HIV.
You are uncertain about your sexual partner's risk behaviors.
You are a male who has had sex with another male at any time since 1977.
Any of your male sexual partners has had sex with another male since 1977.
You have used street drugs by injection since 1977, especially when sharing needles and/or other equipment.
When should the test be taken?
After a possible HIV exposure:
An HIV test will not detect the presence of the HIV virus immediately after exposure. Statistics show that 96% (perhaps higher) of all infected individuals will test positive within 2 to 12 weeks. In some cases, this may take up to six months.
Think about this: if you got a negative test at six weeks, would you believe it? Would it make you less anxious? If so, go for it. But to be certain, you will need to be tested again at six months.
Periodic Testing:
* Many people continue to engage in some degree of risky behavior, and choose to be tested for HIV periodically (every six months, every year, or every other year.)
Since the window period for developing a positive test result can be as long as six months, it would rarely make sense to be tested more often than this.
There are clear benefits to early medical attention for infection with the HIV virus. There is little agreement on how early this must be. But if you wait longer than two years, treatment of the disease may be less effective.
* If you are beyond the six month window period from a possible HIV transmission event and were reported HIV negative by an accurate HIV test (and you are not subsequently put at risk for HIV), you can consider yourself HIV negative. There is no need to retest. However if it eases your anxiety, you may wish to take the test again periodically.
Elisa or EIA Test
Elisa or EIA (enzyme immunoassay) is the standard screening test used to detect the presence of antibodies to HIV.
This test looks for HIV antibodies in a person's blood. When HIV enters a person's body, special chemicals are produced. These are called antibodies. Antibodies are the body's response to an infection. So if a person has antibodies to HIV in their blood, it means they have been infected with HIV (an exception is the case of an HIV negative baby born to a positive mother, who will retain her antibodies for some months). Depending on the clinic, the test results can take from a few days up to three weeks.
If this test is positive, it must be confirmed with a second test called the Western Blot which is a more specific test and will confirm if someone is truly HIV positive, as there are other conditions which may give a false positive ELISA screening test (eg. lupus, lyme disease, syphilis).
Other types of HIV test
In addition to the EIA, other tests now available include:
Radioimmunoprecipitation assay (RIPA): A confirmatory blood test that may be used when antibody levels are very low or difficult to detect or when Western blot test results are uncertain. An expensive test, the RIPA requires time and expertise to perform.
Rapid latex agglutination assay: A simplified, inexpensive blood test that may prove useful in medically disadvantaged areas where there is a high prevalence of HIV infection.
Dot-blot immunobinding assay: A rapid-screening blood test that is cost-effective and that may become an alternative to conventional EIA and Western Blot testing.
p24 antigen capture assay: Also known as the HIV-1 antigen capture assay. This blood test was added as an interim measure by the Food and Drug Administration (FDA) in 1996 to HIV-antibody testing to protect the blood supply further until other tests become available to detect early HIV infection before antibodies are fully developed. Because some activity of p24 antigen is unpredictable, this test is not useful for helping people find out if they have HIV.
Polymerase chain reaction (PCR): A specialized blood test that looks for HIV genetic information. Although expensive and labor-intensive, the test can detect the virus even in someone only recently infected. To further protect the blood supply, the FDA has indicated that the development and implementation of tests for HIV genetic material such as PCR is warranted.
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