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What Are HIV Antibody Tests

As the body fights viruses, it creates antibodies to that virus. HIV antibody tests measure the presence of antibodies to HIV. They do not measure or detect the virus itself. There are three commonly used antibody tests.

Three Kinds of HIV Antibody Tests

ELISA

The ELISA is almost always the first screening tool; it is inexpensive and very sensitive. In most cases, a blood sample is tested, but other types of ELISA's that use saliva and urine have also been developed. The actual ELISA takes 3.5 to 4 hours, but most test sites send samples to outside labs, where they are tested in batches, so you may have to wait one to two weeks for results. Beyond the "window period," discussed above, ELISA tests are very rarely "false negative." This means if you have a negative test result, and you were tested at least six months after the last potential exposure, you are really HIV negative. An ELISA test may rarely be "false positive." False positive ELISA results can occur if someone is tested right after events that temporarily stimulate the immune system, such as viral infections or immunizations. They could also occur because of lab error, or because of the test's very high sensitivity, discussed below. For these reasons, positive ELISA results must always be confirmed with a Western Blot or IFA (below), and at reputable test sites this is commonly done automatically -- meaning you don't have to come for another blood draw.

Western Blot (WB) Assay

The WB is a confirmatory test. It is only performed if the ELISA is positive. The WB can be positive, negative, or indeterminate. Indeterminate tests are neither positive nor negative. An indeterminate result usually means that a person has just begun to seroconvert at the time of their test. In the rare cases in which this occurs, the person ,will need to be re-tested, usually about one month later. False positive results are extremely rare with the WB, so it confirms (proves) that HIV antibodies are present.

Detuned ELISA

A relatively new test, called a detuned ELISA, which has been used in research settings, will soon become more widely available to other test sites. The detuned test, which is used only after HIV antibodies are confirmed by a Western Blot, can determine if the HIV infection is recent (within the last six months), which may be useful for deciding upon possible early treatment options.

Why Be Tested: PROS AND CONS

Pros

• If you know you are HIV-positive, you can take advantage of immune system monitoring and early treatment and intervention.
• By taking the test, you can find out whether or not you can infect others.
• Regardless of the result, testing often increases your commitment to overall good health habits.
• If you test negative, you may feel less anxious after testing.
• Women and their partners considering pregnancy can take advantage of treatments that potentially prevent transmission of HIV to the baby.

Cons

• If you test positive, you may show an increase in anxiety and depression.
• When testing is not strictly anonymous, you risk job and insurance discrimination. However, you can prevent this by ensuring that you test at an anonymous testing site.

Whether or not to take the antibody test is an extremely personal decision. We cannot make that decision for anyone. We can only advise you of the implications of testing. The decision to test is yours.

Window Period

When we become infected with any virus (cold virus, flu virus, HIV virus, etc.), our immune system produces antibodies which are used to destroy that particular virus. However, the antibodies we produce to fight HIV are not capable of destroying HIV.
The "window period" is the time it takes for a person who has been infected with HIV to produce antibodies to the virus. This production of antibodies is called seroconversion. Antibodies to the HIV virus will appear within 3 months of infection.
You may be anxious to be tested soon after an encounter which you perceive to be risky. You may want to know: can I be tested without waiting three months? How accurate is the test after six weeks? Think about this: if you got a negative test at six weeks, would it be accurate? It is best to wait until 3 months after the risky encounter before getting tested so that it is entirely accurate. If testing will make you less anxious then go ahead and get tested. But remember, to be certain, you will need to get tested again after 3 months following the risky encounter.

Test Results

A Positive Result Means

• You are HIV-positive (you are carrying the virus that causes AIDS).
• You can infect others and should try to take precautions to prevent doing so.

A Positive Result Does NOT Mean

• You have AIDS.
• You will necessarily get AIDS.
• You are immune to AIDS, even though you have antibodies.

A Negative Result Means

• No HIV antibodies were found in your blood at this time.

A Negative Result Does NOT Mean

• You are not infected with HIV (you may still be in the "window period").
• You are immune to AIDS.
• You have a "resistance" to infection.
• You will never get AIDS. You may wish to consider avoiding unsafe activities to protect yourself.

Anonymous HIV Testing ( Not available in Prince Edward Island)

• Anonymous testing means that absolutely no one has access to your test results since your name is never recorded at the test site.
• Anonymous test sites are highly recommended because:
• The quality of the education and counseling is very good.
• The testing is usually free.
• The testing is reliable and automatically includes confirmatory tests.
• It protects you from risks of discrimination or adverse impact, especially in applications for insurance. Sometimes even taking an HIV test, regardless of the result, might cause an insurance application to be refused. Anonymous testing sites never give written results. Some sites who do anonymous testing also do confidential testing, which may include written results.
At some anonymous test sites, you must make an appointment; in others, appointments are not necessary--you may drop in. You choose, or are given, a letter/number code that will match you to your test results. Most anonymous test sites provide pre-test counseling and risk assessment. A blood sample is drawn. You must return, in person, in approximately two weeks to obtain results.

Confidential HIV Testing (Method done in Prince Edward Island)

HIV antibody testing is available through physicians, some clinics, and hospitals. If you give your name, even if the test site says your name is known only to them and not the lab, the test is confidential, not anonymous. Confidential antibody testing means that you and the health care provider know your results, which may be recorded in your medical file.
Some physicians might agree to omit the test results from the medical file. In some cases, doctors have been known to keep separate files, one for the insurance companies and one for private use with the patient. However, this is probably risky for the doctor.

Some reasons for confidential testing are:

• A written result is required for immigration purposes or for some international travel visas.
• A pregnant woman who is clearly at risk might choose to be tested through her doctor, rather than anonymously, since the result is of key importance to the course of her medical care.
• Potentially faster linkage to medical care.

You may simply choose to not go to the anonymous testing site, and that is certainly your option. Some people may want written results for the wrong reasons, e.g. to be a "card-carrying HIV-negative sexual partner." We discourage this reasoning, as no written test result can accurately indicate a person's negative HIV status. Remember the three to six month window period and the fact that someone could have been exposed to HIV after being tested.

For more information call AIDS PEI at 566-2437.