Lesson 7 

When we hear about the percentage of people in our country who are HIV positive, we may become anxious about our HIV status. Also, when we hear about the death from AIDS complications of a neighbour, relation or friend, we get worried as to whether or not we have HIV. In order to get our worries allayed, we need to do a test for HIV.

After completing this lesson, you should be able to

• state reasons why a person should test for HIV;
• describe commonly used tests for HIV;
• interpret results of an HIV test; and
• share knowledge with your students about HIV testing.

Need for HIV testing

Getting tested for HIV is a smart thing to do. Yet many people refuse to get tested. They find the idea of getting tested so frightening they just do not want to do it, even though they will often continue to be stressed and worried about whether they are infected. Others think of testing as unnecessary because they want to believe that they cannot be infected with HIV.

Many times when someone gets tested, they happily find out their concern about being infected was unfounded. Getting the assurance of that negative test result can provide an enormous relief. For others, getting tested and learning they are HIV positive is the first important step towards staying healthy.

Being unaware of HIV status also makes it more likely for a person to unknowingly pass the HIV virus to others. One of the most basic truths about HIV is that gender, age, race and economic status are irrelevant when it comes to vulnerability to HIV. Anyone can become infected.

Who Should Be Tested?

Testing is recommended for those who:

• have multiple sexual partners (2 or more sexual partners in the last 12 months)
• have received a blood transfusion recently in a place where blood is not screened before transfusion, or if a sexual partner received a transfusion and later tested positive for HIV.
• are uncertain about their sexual partner's risk behaviours.
• are homosexuals
• have used street drugs by injection especially when sharing needles and/or other equipment.
• have a sexually transmitted disease (STD), including pelvic inflammatory disease (PID).
• are health care workers with direct exposure to blood on the job.
• want to make sure they are not infected with HIV before getting pregnant.
• are infected with tuberculosis.

Even if you have no risk factors for HIV infection, you may still want to get tested to ease your own mind. This also encourages everyone to be more responsible about HIV transmission.

HIV Tests

Since HIV was first identified as the cause of AIDS in 1983, a variety of tests have been developed for diagnosing HIV infection as well as determine how far the infection has progressed. Doctors determine if HIV is present in the body by identifying HIV antibodies, specialised proteins created by the immune system to destroy HIV. The presence of the antibodies indicates HIV infection because these antibodies form in the body only when HIV is present. HIV antibodies form anywhere from five weeks to three months after HIV infection occurs, depending upon the individual’s immune system. The antibodies are produced continually throughout the course of the infection. There is a "window period" which is the time it takes the body to produce antibodies after HIV infection has begun. For the vast majority of those who will test positive, antibodies to HIV will develop within 4-6 weeks after exposure. Thus, to receive a reliable test result, it is necessary to wait at least three months (13 weeks) after the last possible exposure to the virus before being tested.

Getting tested before three months may result in an unclear result or a false negative. Some testing centres may recommend testing again at six months. All but less than 1% of those who are going to seroconvert will do so within three months (seroconversion is the development of detectable antibodies to HIV in the blood as a result of infection.) It is extremely rare for seroconversion to take more than six months to develop detectable antibodies.

There are a number of tests for the presence of the HIV virus. Generally speaking, these tests yield conclusive results within 48 to 72 hours after infection has occurred. However, in some cases, it can take as long as 28 days for results to be considered accurate. Some of these tests are described below.

The ELISA AND WESTERN BLOT TEST

The standard test for detecting HIV antibodies in the blood is the enzyme-linked immunosorbent assay (ELISA). In this test, a blood sample is mixed with proteins from HIV. If the blood contains HIV antibodies, they attach to the HIV proteins, producing a telltale colour change in the mixture. This test is highly reliable when performed two to three months after infection with HIV. The test is less reliable when used in the very early stage of HIV infection, before detectable levels of antibodies have had a chance to form. Doctors routinely confirm a positive result from an ELISA test by using the Western Blot test, which can detect lower levels of HIV antibodies. In this test a blood sample is applied to a paper strip containing HIV proteins. If HIV antibodies are present in the blood, they bind to the HIV proteins, producing a color change on the paper. The combination of the ELISA and the Western Blot test is more than 99.9 percent accurate in detecting HIV infection within 12 weeks following exposure.

P24 Antigen Test: This test uses ELISA technology to look directly for key pieces of the HIV virus – the p24 protein found on HIV's outer coat. This test can reduce the chance of a false-negative in standard (antibody) ELISA testing if it is done too early (i.e., less than 13 weeks after exposure). The p24 antigen test may be ordered if there is a very recent risky exposure to HIV, such as a healthcare work-related incident. Blood banks also use it for screening donations. The test is valuable in detecting HIV infection early in the window period after exposure, this test is only useful for a period of approximately three weeks after exposure, before the production of antibodies begins. A p24 test result should be confirmed by antibody testing once the window period has passed.
 

Viral Load Test

Viral load testing measures the amount of new virus being produced and released into the bloodstream. Several studies have shown that higher levels of viral load are associated with more rapid disease progression and a greater risk of death. Lower levels are associated with stability and reduced risk of progression, infection, or death. Ideally, an HIV infected person should have no detectable level of virus, which means that the level of virus activity is too low to be measured. Currently available tests measure down as low as 200 to 500 copies of virus, the lowest amount presently measurable. This is associated with the best possible clinical outcome. Higher levels, ranging from several hundred upwards of millions of copies of virus, are associated with higher rates of disease progression. In short, the higher the number, the more rapid the rate of disease progression.

The viral load test gives a more accurate picture of the rate of disease progression. There are two commonly available tests for measuring viral load. One is called "quantitative PCR" (or "Q-PCR"), the other "branched DNA" (or "b-DNA"). Though there are small differences between the two tests, they are for practical purposes one and the same.

The Quantitative Polymerase Chain Reaction (QPCR): is considered to be highly reliable for someone who may have recently been exposed to the virus, particularly in a high-risk situation. If the virus is present, the quantitative PCR will reveal how much virus is in a person's bloodstream (the viral load). In most cases, a quantitative PCR is highly accurate within 48 to 72 hours. However, a small number of people do not have viral loads that are high enough to confirm a diagnosis until 28 days after exposure.  The standard recommendation is that a negative PCR result be confirmed with an ELISA test at 13 weeks.
 

Qualitative PCR: The qualitative PCR, also known as the PCR-DNA test, looks for DNA in cells that suggest that HIV infection has taken place. It is not a viral load test, meaning that it will only determine if the virus is present, not how much virus is present. This test is frequently used to determine if an infant born to an HIV-positive is infected with the virus, given that it can detect virus before viral load becomes detectable. However, it is not at all clear if the qualitative PCR test has any advantages over the quantitative PCR test, which appears to be just as reliable, more widely available, and cheaper to perform.
 

Clinical trials of new drugs use these tests to measure the effect of drugs. A good antiviral drug can quickly reduce the level of virus at least ten fold and often as much as a thousand fold. The goal of  therapy is to reduce the viral load to the lowest level detected by the test, usually below 200-500 viral copies.

HIV infected people and their physicians use these tests to make decisions about when and if to use antiviral drugs, and to determine if a drug is working on not. When the virus levels begin to rise again while using a drug, most physicians believe it is time to switch to another drug or combination of drugs.

Knowing the viral load helps doctors estimate an infected person’s survival time. For example, studies show that without treatment, the average survival time for people with an HIV viral load greater than 30,000 per microlitre of blood is 4.4 years, while those with a viral load below 10,000 per microlitre of blood live for an average of ten years.

CD4+ Testing

For many years, testing the number of CD4+ cells was the most common way to measure the effects of HIV disease. Low numbers of these cells (below 200) accurately predicts the risk of major infections. The meaning of test results in between this critical level of 200 and the normal level of 1000 is unclear. Physicians once typically started treatment for people when the CD4+ was below 500, but this was always an arbitrary number simply selected from clinical trials. By itself, this number does not tell us enough about the state of disease. It only shows that the level of CD4+ cells is below normal, to varying degrees. Getting the full picture of HIV disease requires additional tests, especially the Viral Load Test.

CD4+ Cell Ranges

Low                Medium       High

(under 300)    (300-500)     (500 plus)

High Range:
In general, a CD4+ count above 500 suggests no immediate danger, even though it may represent a loss of half the normal CD4+ cell count (1000). The 500 level is sometimes cited as the bottom of the "normal" range, but this can be misleading. While an occasional drop to 500 may be normal, a steady or falling count of 500 or even 600 is not normal and indicates suppressed immunity. At the very least, dietary counselling, nutritional supplements, CD4+ cell monitoring, and periodic use of other tests are recommended in this range, whether or not treatments are used.

Medium Range:
CD4+ counts in this range indicate significant decline of the immune system. However, serious symptoms are uncommon in this range. Some researchers believe this is the optimum time to begin treatment, especially if the viral load test also indicates significant viral activity.

Low Range:
CD4+ counts below 300 indicate the greatest risk of infections and according to the 1993 definition of AIDS, a CD4+ count of 200 or less constitutes an AIDS diagnosis. A person with counts below 300 CD4+ may remain stable for many years, especially with careful health management. While some people have warning signs in the form of symptoms before major infections occur, this is not always the case

How Testing is Done

Rapid Testing: A blood sample is obtained through finger stick and analyzed using the ELISA test. The results are usually available within ten to sixty minutes. If the result is positive, a follow-up test is required, usually by drawing blood and sending the sample to a laboratory for Western blot testing. If the result is negative, there is no need for additional testing and the result can be considered conclusive.  Convenient and faster, this method is often used in healthcare settings, particularly where urgency is an issue such as with someone who is pregnant or about to give birth. Because it provides a result so quickly, this is an increasingly popular method for testing.

Oral Fluid Test: A device is used to collect oral (mouth) fluid (i.e. saliva). Oral fluids can contain antibodies to HIV, which can be detected using the ELISA and Western blot tests. Typically, it takes one to two weeks to get a result. Because it is so easy and comfortable to accomplish, this test is often used in clinics, doctors' offices, hospitals, and school-based and university health centres.

 

Urine-Based Test: A urine sample, collected in a cup, is used for the ELISA/Western blot tests. The results of this non-invasive and non-technical method can be obtained typically in one to two weeks. It is commonly used in community-based and outreach settings, adolescent, school and university-based settings. Anyone with a positive urine result must have a confirmatory test.             

What Do My Test Results Mean?

A negative test result means:

• If you have not engaged in any risky behaviours for the last 6 months, you are not currently infected with HIV. If you have had unprotected sex or shared needles or have other risk factors in the last 6 months, you should be tested again. You could still be HIV positive, and pass the HIV on to other people, even though your test is negative.
• A negative test does not mean that you are immune to HIV.
• Some people who have a negative test may be tempted to continue risk behaviours, believing "It can't happen to me." If you continue unsafe behaviours, you are still at risk.

A positive test result means:

• The person is infected with HIV. This does not necessarily mean that he/she has AIDS.
• A person with HIV is infected for life. He or she can pass the virus to others by having unprotected sex, or by sharing drug use needles or equipment. To protect yourself and others, you need to avoid doing these things. A woman who has HIV can pass it on to her unborn or breast feeding baby. Those carrying the HIV should not donate blood, plasma, semen, body organs, or other tissue.
• One should get a doctor to monitor the progression of HIV in the body, and advise on when it is appropriate to begin treatment. There are differing opinions about how early to begin treatment, but it is clearly much better to begin treatment long before symptoms of AIDS develop.
• If one’s HIV test is positive, sexual partners and anyone with whom one has shared drug injection equipment may also be infected. They should be told they have been exposed to HIV and advised to seek HIV counselling and antibody testing.

Need for periodic testing

Many people continue to engage in some degree of risky behaviour, 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.

 

Resources: Chart A showing (i) a person having his blood drawn preparatory to being tested for HIV and (ii) a person pricking self ready to test for HIV using HIV testing kit; Chart B listing different types of HIV test; and Chart C showing low, medium and high viral loads.

Procedure:

Step 1: In small groups, ask students to discuss why people should test for HIV and the procedure commonly adopted. Request a member of each group to present the summary of the group’s discussion to the whole class. List the summaries on the board.

Step 2: Engage pupils in interactive discussion on the class summaries, giving further explanation on why people should be tested for HIV. Request pupils to consider taking the HIV test and in turn, to encourage member of their family and friends to take the test at the nearest clinic where such facility exists.

Step 3: Using Charts A and B, discuss with pupils the following HIV tests:

The ELISA and Western Blot Test

The standard test for detecting HIV antibodies in the blood is the enzyme-linked immunosorbent assay (ELISA). In this test, a blood sample is mixed with proteins from HIV. If the blood contains HIV antibodies, they attach to the HIV proteins, producing a telltale colour change in the mixture. This test is highly reliable when performed two to three months after infection with HIV. Doctors routinely confirm a positive result from an ELISA test by using the Western Blot test, which can detect lower levels of HIV antibodies.
 

Viral Load Test

Viral load testing measures the amount of new virus being produced and released into the bloodstream. Higher levels, ranging from several hundred upwards of millions of copies of virus, are associated with higher rates of disease progression. In short, the higher the number, the more rapid the rate of disease progression.

Using Chart C, explain to the pupils the meanings of the results of HIV tests.  Let pupils lead the discussion on what should be done when the result is (a) positive; and (b) negative. Contribute the following to the discussion.

If the result is negative:

• you are not currently infected with HIV if you have not engaged in any risky behaviours for the last 6 months,. If you have had unprotected sex or shared needles or have other risk factors in the last 6 months, you should be tested again. You could still be HIV positive, and pass the HIV on to other people, even though your test is negative.
• A negative test does not mean that you are immune to HIV.
• Some people who have a negative test may be tempted to continue risk behaviours, believing "It can't happen to me." If you continue unsafe behaviours, you are still at risk.

A positive test result means:

• The person is infected with HIV. This does not necessarily mean that he/she has AIDS.
• A person with HIV is infected for life. He or she can pass the virus to others by having unprotected sex, or by sharing drug use needles or equipment. To protect yourself and others, you need to avoid doing these things. A woman who has HIV can pass it on to her unborn or breast feeding baby. Those carrying the HIV should not donate blood, plasma, semen, body organs, or other tissue.
• One should get a doctor to monitor the progression of HIV in the body, and advise on when it is appropriate to begin treatment. There are differing opinions about how early to begin treatment, but it is clearly much better to begin treatment long before symptoms of AIDS develop.
• If one’s HIV test is positive, sexual partners and anyone with whom one has shared drug injection equipment may also be infected. They should be told they have been exposed to HIV and advised to seek HIV counselling and antibody testing.

Step 4: Close the lesson with a summary and review questions.

In this lesson, we learned the following:

Testing is recommended for those who:

• have multiple sexual partners (2 or more sexual partners in the last 12 months)
• have received a blood transfusion recently in a place where blood is not screened before transfusion, or if a sexual partner received a transfusion and later tested positive for HIV.
• are uncertain about their sexual partner's risk behaviours.
• are homosexuals
• have used street drugs by injection especially when sharing needles and/or other equipment.
• have a sexually transmitted disease (STD), including pelvic inflammatory disease (PID).
• are health care workers with direct exposure to blood on the job.
• wants to make sure they are not infected with HIV before getting pregnant.

The standard test for detecting HIV antibodies in the blood is the enzyme-linked immunosorbent assay (ELISA). In this test, a blood sample is mixed with proteins from HIV. If the blood contains HIV antibodies, they attach to the HIV proteins, producing a telltale colour change in the mixture. This test is highly reliable when performed two to three months after infection with HIV. The test is less reliable when used in the very early stage of HIV infection, before detectable levels of antibodies have had a chance to form. Doctors routinely confirm a positive result from an ELISA test by using the Western Blot test, which can detect lower levels of HIV antibodies.

The P24 Antigen Test uses ELISA technology to look directly for key

pieces of the HIV virus – the p24 protein found on HIV's outer coat. This test can reduce the chance of a false-negative in standard (antibody) ELISA testing if it is done too early (i.e., less than 13 weeks after exposure).

Viral load testing measures the amount of new virus being produced and released into the bloodstream.

In general, a CD4+ count above 500 suggests no immediate danger, even though it may represent a loss of half the normal CD4+ cell count (1000). The 500 level is sometimes cited as the bottom of the "normal" range, but this can be misleading. While an occasional drop to 500 may be normal, a steady or falling count of 500 or even 600 is not normal and indicates suppressed immunity.

Testing methods include (a) Rapid Testing: A blood sample is obtained through finger stick and analyzed using the ELISA test; (b) Oral Fluid Test: A device is used to collect oral (mouth) fluid (i.e. saliva). Oral fluids can contain antibodies to HIV, which can be detected using the ELISA and Western blot tests; and (c) Urine-Based Test: A urine sample, collected in a cup, is used for the ELISA/Western blot tests. The results of this non-invasive and non-technical method can be obtained typically in one to two weeks. It is commonly used in community-based and outreach settings, adolescent, school and university-based settings. Anyone with a positive urine result must have a confirmatory test.