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HIV Testing

January 8, 2009

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Why Should You Get Tested for HIV?

The federal Centers for Disease Control and Prevention (CDC) estimates that 38% to 44% of all adults in the United States have been tested for HIV and that between 16 and 22 million people aged 18-64 years are tested for HIV annually. However, of more than one million people living with HIV in the U.S., it is estimated that about one-quarter (252,000 to 312,000 persons) are unaware of their HIV status. Because they do not know they are infected, these individuals are unable to benefit from clinical care related to their HIV disease. In addition, some of these people may unknowingly be transmitting HIV to other people. The San Francisco AIDS Foundation strongly encourages people who are at risk for HIV to be tested regularly. Whether or not to take the HIV antibody test, however, is a personal decision that only you can make for yourself. That being said, here are some things you may wish to consider:

  • Knowledge is power.
  • If you find out that you are HIV-positive (infected with HIV), you and your healthcare providers can better plan early treatment and intervention, improving your chances of slowing down the progression of HIV disease.
  • If you test negative, you may feel less anxious.
  • By knowing your status, you can find out whether or not you can infect others, and what precautions you might take to prevent transmission to other people.
  • Regardless of the result, testing tends to increase your commitment to overall good health habits. If you test positive, you can learn more about HIV and be proactive in taking care of your health.
  • If you are considering having a baby, you can take advantage of treatments that potentially prevent transmission of HIV to the baby.


What Are HIV Antibody Tests?

As the body fights viruses, the immune system creates antibodies to that virus. HIV antibody tests do not measure or detect the virus itself but instead look for your body's reaction to the virus -- the presence of antibodies to HIV.

ELISA

The ELISA (also sometimes called EIA) is often used as the first screening tool. It is inexpensive and very sensitive for detecting the presence of HIV antibodies. In most cases, a blood sample is tested, but other types of ELISAs 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 ELISA tests are very rarely "false negative." This means if you have a negative test result, and you had met the Window Period guidelines 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 have another blood sample drawn.

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 test, can determine if the HIV infection is recent (within the last six months), which may be useful for deciding upon possible early treatment options.

Western Blot (WB) Assay

The WB is a confirmatory test: it is only performed if an ELISA or rapid test 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 retested, usually about one month later. False positive results are extremely rare with the WB, so it confirms (proves) that HIV antibodies are present.

Indirect Immunofluorescence Assay (IFA)

The IFA can be used instead of the WB to confirm ELISA results. Like the WB, IFA tests for the presence of antibodies in a blood sample. The exact strategy is slightly different in that it uses a microscope. It can be faster than a WB, so the few labs that use it can get results to the patient more quickly.


Rapid Tests for HIV

Rapid testing for HIV has become one of the most prominent ways that people receive HIV tests today. In as little as 20 minutes, you can find out your HIV status.

Rapid tests work similarly to traditional HIV test: they look for antibodies to HIV, not the virus itself. Most commonly, a rapid test is adminestered by sampling the oral mucosa (the mucous that is everywhere in your mouth) and putting it through a test to see if HIV antibodies are present.

Some people may think that, since the test uses the mouth to test for HIV, that HIV can be transmitted to other people through saliva, spit and/or oral mucosa via kissing, sharing utensils, or sharing glasses. This is not true. For more information, see this website's section on How HIV is Spread.

A rapid test runs for 20-40 minutes, after which you will receive a result. Rapid tests are extremely accurate. However, since rapid tests have a small margin of error (ranging from 1 to 3 per 1,000), all positive (reactive) results have to be put through a confirmatory test.

The most common type of rapid test currently in use in Callifornia is the OraQuick Advance. The availability of rapid tests varies by city. Some testing locations in California charge for this type of test, but there are many locations that will provide the test for free. For testing locations, you can call the California HIV/AIDS Hotline at 1-800-367-AIDS or you can do your own referral search by visiting www.aidshotline.org.


Window Period

The "window period" is the time it takes for a person who has been infected with HIV to react to the virus by creating HIV antibodies. This is called seroconversion.

During the window period, people infected with HIV have no antibodies in their blood that can be detected by an HIV test, even though the person may already have high levels of HIV in their blood, sexual fluids, or breast milk.

Here is what the CDC says about the window period:

"Antibodies generally appear within three months after infection with HIV, but may take up to six months in some persons."

This CDC definition of a three to six month window period has been commonly used for a number of years.

What does this mean for you?

  • The three month window period is normal for most of the population. Many people will have detectable antibodies in three or four weeks. Very, very rarely (i.e., only a few cases ever), a person could take six months to produce antibodies.
  • You may be anxious to be tested soon after an encounter which you perceive to be risky (for a discussion of what behaviors put you at risk for HIV and which ones do not, see the section on How HIV Is Spread). You want to know: can I be antibody tested without waiting three months? How accurate is the test after, say, six weeks?

    Unfortunately, we simply don't know.

    Think about this: if you got a negative test at six weeks, would you believe it? Would it make you less anxious? If so, then go for it. But to be certain, you will need to be tested again at three months. Some test centers may recommend testing again at six months, just to be extra sure.

Although HIV may not be detected by a test during the window period, HIV can be transmitted during that time. In fact, individuals are often most infectious during this time (shortly after they have been exposed to HIV).


Interpretation of Test Results

A positive (reactive) result means:

  • You are HIV-positive (carrying the virus that causes AIDS).
  • You can infect others who come into contact with your blood, semen or vaginal fluid. You should take necessary precautions to avoid transmitting HIV to others.

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 (non-reactive) 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 HIV.
  • You have a "resistance" to infection.
  • You will never get HIV.

An indeterminate result (which is rare) means:

  • The Western Blot (WB) result is unclear. The entire HIV test must be repeated with a new blood sample, usually several weeks after the first blood test.
  • Indeterminate results usually occur if the test is performed just as the person begins to seroconvert.


Accuracy of Antibody Tests

Antibody tests are extremely accurate, whether receiving a rapid test or a more traditional ELISA. Rapid test, for example, have an accuracy rate exceeding 99%. However, positive results from a rapid or ELISA test must be confirmed by another test to ensure that a person is HIV-positive.

The accuracy of a medical test is a combination of two factors: sensitivity and specificity. The ELISA is extremely sensitive (about 99.5%), which means it will detect very small quantities of HIV antibody. This high sensitivity reduces the odds of reporting a "false negative" when HIV antibodies are present. Assuming you are being tested beyond the "window period" and have not engaged in activities that put you at risk for HIV, if the ELISA is "negative," there is virtually no chance you have HIV.

The high sensitivity of the test creates a slightly lower specificity. This means the result could (infrequently) be "false positive." To compensate for this, confirmatory tests are automatically performed after a positive ELISA. The WB and IFA are highly specific for HIV antibodies, so they rule out false positive ELISAs nearly every time.

The CDC states that the combined accuracy of the ELISA plus either the WB or IFA is greater than 99%.

The CDC recommends retesting any positive (reactive) ELISA twice; if either retest is positive (reactive), then a confirmatory test is performed. Only when the confirmatory test is also reactive is the result reported as HIV positive. Again, reputable test sites automatically follow this procedure, so results reported to you as positive can be relied upon completely. It is also important to note that if you test positive through the use of a rapid HIV test (with results provided in 20 minutes or less), your result is still preliminary. A confirmatory test must be performed to verify whether you are infected with HIV and these results will take several days.

What does this mean for you?

  • If you are beyond the window period and were reported HIV negative by a rapid test or an ELISA, and you are not subsequently at risk for HIV, you should consider yourself HIV negative.
    If you want to discuss these issues further -- for example, you want to find out if a certain activity put you at risk for getting HIV -- call an AIDS hotline. Within California, call the San Francisco AIDS Foundation's California AIDS Hotline toll free at 800/367-AIDS. Outside California, call your state's AIDS Hotline or the CDC-INFO toll free at 800/CDC-INFO. To find the number for your state's aids hotline, go to www.aidshotline.org and click on Other AIDS Hotlines.
  • Some individuals, perhaps wanting results without waiting for the window period, may be curious about a PCR or other types of viral load (RNA) testing (testing directly for the virus itself). Viral load testing is generally used to allow physicians to track with great accuracy the progression of HIV in the body -- thus helping HIV-infected patients make choices about appropriate treatment strategies. Most people concerned about their HIV status do not need viral load testing. The antibody test is the cheapest, easiest, and overall most reliable way for individuals to learn their HIV status.

That being said, individuals who have had a recent exposure to HIV and experience symptoms consistent with seroconversion (flu-like symptoms), can request a viral load test from their doctor in addition to the HIV antibody test. This may help identify HIV infection during the window period (before HIV antibodies have developed), though it should be noted that an antibody test is ultimately needed to confirm that one is HIV-infected.


Anonymous HIV Testing

Free anonymous testing is available at Anonymous Test Sites in most counties in California. Anonymous testing means that no one has access to your test results since your name is never recorded at the test site.

Anonymous test sites are preferred by some individuals because:

  • The quality of the education and counseling is usually very good.
  • The testing is usually free.
  • The testing is reliable and automatically includes confirmatory tests.
  • It protects you from any and all risks of discrimination or adverse impact.

People with HIV infection and AIDS are generally reported by name to local and state public health officials (see HIV name reporting section below). Anonymous test results, however, are not reported to the government and can not be because an individual's name is never provided. In addition, anonymous testing sites never give written results. Some sites that provide anonymous testing also provide confidential testing, which may include written results. If you live in California, visit www.aidshotline.org to find sites that offer anonymous or confidential testing or you can call the California AIDS Hotline, toll free, at 1-800-367-AIDS.

At some anonymous test sites, you must make an appointment; in others, appointments are not necessary -- you can just 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 sometimes drawn, but some sites now use rapid HIV testing, which can be done needle-free or utilizes blood taken from a finger-stick. You must return, in person, in about one to two weeks to obtain results, unless the rapid HIV test is used, which can determine your results in less than 20 minutes.


Confidential HIV Testing

HIV antibody testing can be ordered through a private physician, 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 technically 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. There are also testing sites that offer confidential testing. Those who are tested confidentially and are found to be infected with HIV are reported to local public health officials so that the government can better track the extent of the disease in the population as a whole.


HIV Name-Based Reporting

California requires those who are infected with HIV to be reported by name to local public health officials. It is important to note that AIDS diagnoses have been reported by name in California and throughout the United States since the early 1980s. The federal Centers for Disease Control and Prevention has urged all states to collect HIV infection reports by name and the vast majority of states now do so.

Fortunately, public health reporting by name has been in place for many years for other communicable diseases and this information has been successfully protected by public health officials. More than 80 other diseases and conditions are currently required to be reported by name in California, including Hepatitis, tuberculosis, syphilis and Chlamydia.

This information is collected to allow public health officials to track these diseases. HIV reporting will make it easier for localities to collect information about the epidemic, providing the government with valid, uniform data for service and prevention planning.

It is important to note that only public health officials have access to the information that is reported; employers and insurance companies do not. Additionally, the names of HIV-positive Californians will only be reported to the county in which they live and to the state. The federal government will only receive a unique code for each HIV-positive individual, not their actual name. California law includes provisions that ensure the highest degree of confidentiality of name-based HIV data and significant financial penalties for inappropriate disclosure of that information. In addition, stringent laws exist at the federal, state and local levels to protect individuals with HIV and AIDS from discrimination in housing, employment and public services.

Because public health reporting data are so carefully protected, California's HIV reporting policy should not discourage you from seeking HIV testing and treatment. For those who do have strong concerns about having their HIV status reported to government officials, it may be advisable to seek out HIV testing at an anonymous test site. Because your name is never provided at an anonymous test site, you cannot be reported to the government. It is important to note, however, that if you test positive at an anonymous test site and then seek care for HIV disease from a physician, you will likely be reported by name at that time.


Partner Notification

Voluntary partner notification programs -- also known as partner counseling and referral services (PCRS) -- allow individuals who have tested positive to get help in notifying previous sex or needle sharing partners that they may have been exposed to HIV. Partner notification programs are not new; they have been used for years with tuberculosis, syphilis, and other communicable diseases.

Through these services you will receive counseling about how to notify partners yourself or you can have a public health officer do it for you. The health official will ask for the names, addresses, e-mails and/or phone numbers of other people (contacts) with whom you have had sex or shared needles. The health department will then try to locate each contact to tell them that they have been exposed to someone with HIV and could be at risk. They will advise these contacts to be tested for HIV. The health department does not disclose the name of the person who has tested positive, but in some cases, it may be obvious to the contact, particularly if he/she has had sex with only one or few other people.


Orasure Test for HIV

The OraSure HIV antibody test method, approved by the FDA in 1996, uses a sample of oral mucus obtained with a specially treated cotton pad that is placed between the cheek and lower gum for two minutes. Testing oral mucus has also been called "oral mucosal transudate testing." It is similar to the rapid oral test. In fact, the same company makes both products. The only difference between the two is the amount of time that it takes to receive your results.

Note: the saliva and oral mucus contain antibodies to HIV, not HIV itself, so HIV is not transmitted through these fluids.

Some public test sites offer this oral test as an alternative to blood testing.

The sample is sent to a lab, where it undergoes an ELISA procedure. All positive ELISA samples undergo a Western Blot confirmatory test (using the same pad).

The combined accuracy of OraSure ELISA and WB procedures is comparable to traditional blood testing, so it is very high.


Home HIV Antibody Tests

At this time, one company, Home Access, offers an FDA-approved at-home antibody test. This test costs about $45 to $70, depending on whether you pay for 72-hour results (they give you a pre-paid express delivery envelope to expedite shipping your sample to the lab) or standard 7-10 day results.

Home Access uses a blood sample from a finger prick, which you then send to a certified laboratory for testing. You must call a toll-free number to register your sample prior to shipping. Enclosed in the test kit is an identifying number. Results take three days to one week. To obtain results, you give the operator the ID number and they will look up the result of the test. This number system provides you with an anonymous test result so your result cannot be reported to anyone else.

Home Access uses traditional ELISA and Western Blot procedures, so the results are as accurate as one would receive with an antibody test at an anonymous testing site. The privacy of the home test offers some consumers more comfort than going to a public test site.

Remember, as with testing at an anonymous or confidential site, you must wait three to six months (the window period) after your potential exposure to take the at-home test, to be certain if the activity you are concerned about did or did not infect you with HIV.

With the availability of the HIV rapid test, some companies are now considering developing a new type of 'at-home' testing that could provide preliminary test results in less than 30 minutes. Similar to at-home pregnancy tests, consumers would be able get these preliminary results at home without having to mail in a blood specimen (as is required by the Home Access test that is currently available). Such a test has not yet been approved by the FDA. It should be noted that even if it is approved, the person being tested still must wait the 'window period' as previously described, and take a 'confirmatory test' if there is a preliminary positive result.


Urine Test for HIV

A test that detects HIV antibodies in urine was approved by the FDA in 1996. This test is not generally available to consumers. It is usually marketed to insurance companies and to other countries. Note: urine has antibodies for HIV, not HIV itself, so HIV is not transmitted by urine. Manufactured by Seradyn, it is called the "Sentinel" test.

A sample of urine is tested at a certified lab, using a modified ELISA procedure. This test must be ordered by a physician; this means the urine HIV test, by definition, is confidential, not anonymous.

Because it is less sensitive than a blood test, positive results must be confirmed by a traditional blood sample (ELISA plus WB).


RNA / NAAT Testing

The "NAT" or "NAAT" test (nucleic acid amplification test) is used to detect the presence of genetic material that is specific to HIV. It is not approved for the use of diagnosis of HIV infection perhaps with the exception of diagnosing infection in newborns of infected mothers who have antibodies to HIV that are transferred from the mother.

However, this test is being increasingly used to detect recent infection at the viral load 'spike' that occurs when HIV is first contracted. This is usually at 2 -- 4 weeks after infection. Although a letter of diagnosis and actual treatment is not given until a three month antibody test is confirmed, this does allow providers to get a patient into health care options sooner. It also lets the client know early on so hopefully they can make risk reducing behavioral choices. It is thought that when this initial infection spike occurs that people are at their most infectious stage, so this test can be used to try and combat that as well.

There is research suggesting that between 10-50% of new infections happen during the acute infection stage. Many feel that identifying and making interventions during this period will greatly reduce infection rates.

A cost-effective and efficient way to combine standard ELISA tests with viral load tests is called a "pooled PCR". Viral load tests are expensive to do individuallys. Instead of performing viral load tests on individual blood samples, they have found a way to combine or "pool" samples and test multiple people's specimens at one time. If a pooled sample tests positive, the laboratory technicians test individual samples in the pool until they find the sample that is positive.


For-Profit Test Sites

There are various for-profit sites that offer HIV testing, but we cannot confirm that they all offer appropriate HIV-related counseling and risk assessment. In addition, many of these companies offer the initial test at a certain publicized fee, but do not tell the consumer that any additional tests (including confirmatory tests) may cost extra.

Most businesses charge a premium because they offer faster results. Remember, standard ELISA tests take only 3.5 hours to do, but most non-profit sites send samples away to central labs to lower costs, which is why their tests are free or low-cost. It is the transit (turnaround) time, not the actual test that takes longer. Some people with high anxiety about exposure may be tempted to use this faster service.


Testing Issues for Specific Populations

Pregnant Women

The number of children reported with AIDS due to perinatal HIV transmission in the United States peaked at 954 in 1992 and declined 95% to 48 in 2004, largely because of the effectiveness of ensuring that pregnant women are encouraged to be tested for HIV and, for those who are infected, to receive treatments that can significantly reduce the risk of transmitting HIV to a newborn. The CDC reports that perinatal transmission rates can be reduced to less than 2% if women are aware that they are infected with HIV and take appropriate treatments to prevent transmission.

Perinatal HIV transmission continues to occur mostly among women who lack prenatal care or who are not offered voluntary HIV counseling and testing during pregnancy. Many of the perinatal HIV infections each year can be attributed to the lack of timely HIV testing and treatment of pregnant women.

However, the antibody test may not be sufficient for a pregnant woman who has had known recent exposure to HIV. In such cases, a viral load test that tests for the actual virus (rather than antibodies) may be ordered by a physician to help the woman make more informed decisions.

Newborns and Children

During pregnancy a mother's antibodies to HIV are transferred to the baby. Therefore, for the first 12-18 months, a child born to an HIV-positive woman will test positive with an antibody test. This does not mean that the child is infected. After 12 to 18 months, the child will shed the mother's antibodies. If he/she is infected, the child will continue to test positive with an antibody test after this period. For this reason, the antibody test is not a reliable indicator of HIV status for children under 18 months. In cases such as these, the viral load test may be used to provide additional information about the child's immune system.

HIV testing may present special problems and situations for children and youth.

  • Children under 12. California's Anonymous Testing Sites will not perform an antibody test on children under 12. Children under 12 have to be tested through a private physician or clinic.
  • Youth 12 to 25 may schedule individual youth appointments at the anonymous testing sites. This means they will receive more personalized counseling from the same counselor before and after the test. See the Referral Database for complete listings of HIV-related services for youth in California (keyword: "adolescents").

Immigrants

[adapted from HIV and Immigrants: A Manual for AIDS Service Providers, published by the National Lawyers Guild with support from the San Francisco AIDS Foundation.]

All applicants for U.S. residence must take an HIV antibody test as part of the compulsory medical exam. Those who test positive are denied residence automatically. This measure also applies to all people requesting change in residence status, including citizenship applications.

Let's say you are an immigrant who has tested HIV positive. Besides worrying about testing HIV positive, you also fear what will happen to you because you are not a U.S. citizen. You may wonder whether your immigration status will change the kind of services you can get. You may ask: Will I be deported? Will I lose my immigration status? Can I work or get public benefits to help me if I need them? Will getting benefits make it hard to get another immigration status? If I can't work or get benefits, is there anything I can do to get another immigration status that will help me?

  • Contact a local immigration assistance agency. For California agencies, go to the Referral Database. Use the keyword "refugee" to find local agencies.
  • Do not go to the United States Citizen and Immigration Services (USCIS), formerly known as Immigration and Naturalization Services (INS), office by yourself. No one should speak to USCIS or go to USCIS before talking to an immigration law expert. If non-citizens go to USCIS by themselves, USCIS may arrest them and remove them from the US before they have had the chance to talk to a lawyer.
  • Become informed about confidential versus anonymous testing. Before taking an INS medical exam, a non-citizen should get tested at a local clinic. Anonymous testing will give them the results without connecting those results to a name and may be safer in these circumstances.

Military Personnel

The Defense Department requires all military personnel on active duty and all members of the reserve and National Guard to be tested for the presence of HIV antibodies at least biennially. Soldiers who receive overseas assignment instructions, or are scheduled for overseas duty that will exceed 179 days, must have tested negative within six months of the departure date.

Soldiers who are infected with HIV will not be deployed outside of the continental United States. Soldiers serving outside the continental U.S who are confirmed as HIV-positive will be expeditiously reassigned to the continental U.S.

The U.S. Army Special Operations Command and Ranger organizations are totally closed to those who are infected with HIV. HIV-positive soldiers may face additional restrictions as determined by the U.S. Department of Defense.

A military doctor can notify the spouse of a reservist, if that reservist has tested positive for HIV.



  
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This article was provided by San Francisco AIDS Foundation. It is a part of the publication AIDS 101. Visit San Francisco AIDS Foundation's Web site to find out more about their activities, publications and services.
 
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