Causecast

by KAREN MURPHY, Contributing Writer

National HIV Testing Day is June 27 and was developed by the National Association of People With AIDS (NAPWA) in partnership with the Centers for Disease Control and Prevention (CDC) to encourage awareness of HIV testing, allowing people to take control of their lives by making informed decisions.

Here’s everything you need to know about HIV testing and how to get tested:

Why get tested.

HIV testing is recommended if you think you may have been exposed to the virus. HIV is spread in the following ways:
•Anal, vaginal or oral sex without a condom. If you have another sexually transmitted disease, your chances of contracting HIV during sex are much higher.
•Direct blood or mucous membrane contact with an infected person’s blood.
•From an infected mother to her child, during pregnancy, birth or breast feeding.
•Sharing needles or equipment for drug use.

AIDS.org suggests testing if any of the following apply to you:
•You think you may have been exposed to the HIV virus. If you’re not sure, take this anonymous survey.
•You are sexually active (3 or more sexual partners in the last 12 months)
•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.
•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.

In addition, the CDC now encourages voluntary HIV testing as a routine part of medical care if you are an adolescent or adult between the ages of 13 to 64. (Maybe the CDC doesn’t think people over 64 have sex?)

When to get tested.

Most people (96% or higher) who are infected with HIV will test positive within 2 to 12 weeks after exposure. The average is 25 days, but a positive result may not occur for up to six months. 97% will develop antibodies in the first three months following the time of their infection.

Even if your initial test after suspected exposure is negative, it’s recommended that a follow-up test be performed after six months. This may cause a lot of worry, but it’s the only way to be sure.

Some people, especially those who engage in unprotected sex or other HIV-at-risk behavior, prefer to be tested routinely: every six months, once a year, etc. Since the outside window for a positive result is six months, it doesn’t make sense to be tested any more frequently than at biannual intervals.

Where to go to get tested.

Testing centers are everywhere, but not all testing sites are created equal. Some offer free testing, some offer one type of test vs. another (blood tests, oral tests, rapid response tests…) but testing sites are accessible to everyone.

Find a test site near you by entering your zip code at hivtest.org (My zip code revealed seven sites within three miles, several of which offered free testing.)

Insider tip: You’ll be tested free whenever you give blood. Bonus: if you’re HIV-negative, you’ve done a good deed. HUGE CAVEAT: If you really suspect you were exposed to HIV, it’s completely irresponsible to attempt to give blood even though your blood will be tested for HIV before distribution; no test is 100% accurate given the wide time window of receiving a positive test result (up to six months from exposure) as well as the possibility of a false negative result. Don’t risk our blood supply.

You can even take an anonymous home test called the Home Access Express, available online for $44.00 or $59.95 depending on rapidity of results (more information below under Types of Tests) if getting to a testing site is impractical.

Anonymous testing.

The UNAIDS/WHO policy statement on HIV Testing states that testing must be done under the following conditions:

•Confidential
•Accompanied by counseling (for those who test positive)
•Conducted with the informed consent of the person being tested

Types of tests.

There are two tests most commonly used, the ELISA and the Western blot test. Both tests involve looking for HIV antibodies that would be present once HIV enters the body and the immune system activates. In other words, most HIV tests look for the HIV antibodies rather than looking for HIV itself.

ELISA: An acronym for “enzyme-linked immunosorbent assay” (aka EIA or “enzyme immunoassay”), the ELISA most commonly uses blood drawn from a vein. A positive ELISA must be followed up with a Western Blot in order to make a positive diagnosis. The ELISA test can also be performed using an oral fluid (not saliva) sample; if this is positive an additional ELISA test will be performed using a blood sample. Since the test is typically performed in a laboratory rather than at the blood drawing site, results from the ELISA test are usually available in one to two weeks. The ELISA test isn’t 100 percent accurate and sometimes gives false positive results.

Western Blot: This test uses a different procedure than the ELISA and is considered the “gold standard” in HIV testing. It’s more expensive to perform, thus it typically isn’t used except to confirm a positive result from an ELISA test. An indeterminate result should be retested; almost all HIV-positive persons with indeterminate Western-Blot results will develop a positive result when tested a month later, and certainly within the six-month window.

Rapid tests: A variety of rapid-response tests are available which use both the ELISA and the Western Blot methods. Results are available after 15-20 minutes, depending on the test. The tests can use blood, plasma or oral fluid, mucosal transudate from the tissues of cheeks and gums, or even urine (again, which type of sample is tested depends on the type of test used). Like the ELISA and the Western Blot tests, these rapid tests use the presence of antibodies to extrapolate that HIV is also present.

Home tests. Presently only one test is approved by the FDA, the Home Access Express HIV-1 Test System, manufactured by Home Access Health Corporation. The patient collects a drop of blood and mails the sample to a laboratory; results and counseling are obtained over the phone. Anonymity is protected through the use of an anonymous personal identification number.

CD4+ T-cell test. A new test has been developed by Australian researchers. It works with a finger-prick blood sample to measure the numbers of CD4+ T-cells in a person’s blood (instead of looking for antibodies like the other tests) and can be performed in the field or anywhere without a lab with results in 30 minutes.

Problems with testing.

There are a number of problems inherent in the testing done commonly today, which was standardized in 1985.

1. Antibody test. The ELISA and the Western Blot both test for the presence of antibodies, not for the virus itself. Antibodies could be present under a variety of conditions and don’t necessarily signify presence of disease. In many diseases the presence of antibodies are considered a sign of immunity (particularly in the absence of symptoms), rather than as indication of a fatal disease, which is the case with HIV.

2. Reading the tests. Both the ELISA and the Western Blot tests are somewhat inconclusive. The ELISA result is a number along a spectrum, along which an arbitrary cutoff point was determined. There are no universal criteria for interpreting the Western blot test, and it is not used as a screening test simply because of the high percentage of indeterminate results.

3. False positive results. False-positive ELISA test results can be caused by a variety of conditions: transfusions, transplantation, or pregnancy, autoimmune disorders, malignancies, alcoholic liver disease, or for reasons that are unclear. Diagnosis of HIV infection is based almost entirely on detection of antibodies to HIV, but there can be misleading cross-reactions between HIV-1 antigens and antibodies formed against other antigens, and these may lead to false-positive reactions. Thus, it may be impossible to relate an antibody response specifically to HIV-1 infection.

4. Indeterminate results. The Western Blot test allows not only for positive and negative results, but also for indeterminate results. There is no standardization in reading these results, so based on the interpretation used (which varies from country to country and organization to organization, it is possible to be positive under one interpretation and indeterminate in another.

5. Rapid tests are less accurate. A 2005 surge in false positive results produced by a much-heralded oral HIV test caused at least six testing sites in Los Angeles, San Francisco and New York to shelve the test entirely. In New York, unexplained increases in the number of false positive results from rapid tests are still being investigated.

6. Contested inconclusive link between HIV and AIDS. It could be that we’re barking down the wrong tree, testing for the wrong thing entirely, with many cases of people with AIDS defining conditions, or at least AIDS-defining low CD4 cell counts, who are continuously testing negative for HIV antibodies.

Bottom line.

Right now we have no perfect HIV testing system, but the commonly accepted wisdom is that certain behaviors (unprotected sex, sharing needles, and everything mentioned above) are linked to the HIV virus. So get tested if you’re in that category. You owe it to yourself and you owe it to those around you.

Photo by Mr. TRONA, flickr