HIV Testing

I. Purpose of HIV Testing A. In order for us to stop the spread of any illness, we need to know if people have it. B. Research has shown that people who know they are HIV positive change their

behaviors to reduce the risk of transmission. C. Knowing status is critical to getting medical services. D. Testing is also done to monitor the pandemic and determine how many people are

infected. E. Testing is important in determining the impact of prevention efforts and

promoting behavior changes. F. Testing is also critical to protecting the nation’s blood supply.

II. Statistics about HIV Testing A. As of 2006, about 60% of adults in the US had never been tested for HIV. B. Why not?

1. 61% say that they don’t believe they are at risk. 2. 21% say that a doctor never recommended it.

C. Most people who are infected with HIV are infected before the age of 25. D. Of those, only 15% know they are HIV positive.

III. Most Likely To Test A. Those most likely to test:

1. African-Americans 2. People with higher education levels 3. People who are separated, divorced or widowed

B. Less Likely To Test 1. Men 2. People over age 50 3. Those between the ages of 18 and 19 4. People with low education level 5. People in rural areas

IV. When To Test A. The timing of testing is critical to results. B. Like many infections, HIV has a window period.

1. The window period is the time between when a person is initially infected and when the virus will be detectable in a test.

2. If a person tests for HIV earlier than this, test results would most likely be negative.

3. Why? Because it takes time for the body to develop antibodies. 4. Experts believe that it can take anywhere from 4-12 weeks (and possibly

up to 6 months) after initial infection for enough antibodies to be present so that they can be detected in a test.

HIV Testing

V. Types of HIV Testing A. Those that detect antibodies:

1. ELISA 2. Western Blot 3. IFA 4. RIPA 5. Orasure/Oraquick 6. Home Testing

B. Those that detect the genetic material of HIV or identify HIV antigens (viral load):

1. PCR

VI. ELISA A. The first test licensed to test for the HIV virus became available in 1985. B. ELISA stands for Enzyme Linked ImmunoSorbent Assay C. ELISA tests for antibodies for the HIV virus. D. It is an indirect test–the presence of antibodies suggests that HIV is present, but it

does not detect the actual virus itself. E. How The Test Works

1. ELISA is a blood test. 2. Once a person’s blood is drawn, it is separated into serum (yellow

liquid) and red blood cells. 3. The serum is placed in a dish called a Microwell plate. 4. The plate has a round bead that has bits of HIV attached to it (HIV

antigen). The sample is left for 1 hour. 5. If antibodies are present in the blood sample, the bead will recognize the

HIV antibodies and attach themselves to the bead. F. Why is ELISA Used

1. Low cost (Between $8 -$75 dollars to perform). 2. Standardized procedure. 3. High reproducibility (process is semi-automated so that numerous tests

can be performed at once). 4. Rapid results (2 ½ – 4 hours). 5. High reliability (99.9%).

G. Results 1. Non-reactive- sample is free of HIV antibodies (HIV negative). 2. Reactive- sample is said to be initially HIV positive and will be tested

again using ELISA. 3. If 2nd test is non-reactive, results are reported as HIV negative; 4. If both tests are reactive, results are considered HIV positive and a

confirmatory test is automatically conducted. H. Indeterminate Results

1. ELISA may return indeterminate results, meaning that the test is neither positive nor negative.

HIV Testing

2. This may be a result of: a. Recent HIV infection (few antibodies to measure) b. Prior blood transfusions, even with non-HIV infected blood c. Prior or current infection with syphilis, malaria, or other viruses d. An autoimmune disease such as lupus or diabetes e. Being a recipient of an experimental HIV vaccine f. Problems with the test procedure itself, such as contamination of

the blood sample.

VII. Western Blot A. Western Blot is considered the confirmatory test for HIV. B. This means that it is used to confirm the results of ELISA if ELISA produces

either positive or indeterminate results. C. Western Blot is a more complex test which detects antibodies to the HIV virus in

a blood sample. D. HIV proteins are used which will react with HIV antibodies if they are present in

a person’s serum. E. How The Test Works

1. HIV proteins are placed on a gel, which then gets an electrical charge. 2. HIV proteins will move quickly through the gel, and each different

protein will arrive at a separate position on the gel. 3. After the proteins of similar size form a band, they are identified based

on the distance they have run in the gel. 4. The protein or bands within the gel are then “blotted”, and transferred

directly, band for band, onto strips of nitrocellulose paper. 5. Test serum (patient’s blood sample) is then added directly to the bands

on the nitrocellulose strip. 6. If antibodies are present in the serum, they will form an antigen-

antibody band, indicating a positive result. F. CDC Guidelines for Positive on the Western Blot

1. Reactivity to at least 2 of the following HIV antigens: a. (Protein) p24 b. (Glycoprotein) gp41 c. Glycoprotein) gp120/160.

2. The Western Blot identifies which of the HIV antigens the antibodies are directed against.

G. Why Western Blot Is Used 1. It is more specific than ELISA. 2. Western Blot is, however, labor intensive. 3. It takes about 12-24 hours to perform. 4. Cost: About $25-$50.

HIV Testing

VIII. Other Antibody Tests A. IFA – Indirect Immunofluoresence Assay:

1. Detects antibodies in serum. 2. The specific antibodies are labeled with a compound that makes them

glow an apple-green color when observed microscopically under ultraviolet light.

B. RIPA- Radioimmunofluoresence Assay 1. Detects very small amounts of HIV antibodies in serum. 2. HIV particles are bound with radioactive isotopes and then incubated

with sample serum. 3. If antibodies are present, they will bind to the radioactive

antigens. 4. This test is much more complex and expensive and is used in limited

situations (ex. testing organ tissue prior to transplant).

IX. Polymerase Chain Reaction (PCR) A. Polymerase Chain Reaction (PCR) test finds the genetic material of the virus. B. It is a direct test, meaning that it does not rely on antibodies. C. PCR is very sensitive—it can detect as few as 6 cells in 150,000 cells of blood. D. However, PCR tests may be negative in people who have been recently infected

(less than 5 days) because the virus may not yet have begun to produce detectable quantities of the virus.

E. Usually sensitive at 10 days after infection. F. In essence, this test looks for viral load because it can tell how much virus is in

the person’s blood stream. G. Results are obtained within 48-72 hours. H. Cost: $150 per test. I. PCR testing is not done as frequently as antibody testing because it requires

technical skill and expensive equipment. J. This test may be done in the weeks after exposure to the virus, or in newborns.

X. Rapid Testing A. There are over 30 different rapid HIV tests on the market worldwide. B. The first FDA approved rapid HIV antibody test was released in 1992. C. One commonly used rapid test is called Oraquick. D. Oraquick uses a swab which collects cells from inside the mouth. E. Results are ready in 20 minutes. F. Cost: $25.00-$35.00

XI. Home Testing A. Only one HIV home collection test system is approved by the FDA. B. The test is called Home Access HIV-1 Test System was approved in 1996. C. It allows blood samples (finger prick) to be taken at home, which people then

send to a laboratory for testing. D. Cost: $44.00

HIV Testing

E. Test results are obtained through a toll free telephone number using a PIN number.

F. Post-test counseling is provided by telephone when results are obtained. G. Reliability: 100%

X. Anonymous HIV Testing A. Anonymous testing means that no one has access to test results since the person’s

name is never recorded at the test site. B. Each person is given a unique identifying code. C. There is no official record of them being tested. D. Positive results cannot be reported by name to public health authorities.

XII. Confidential HIV Testing A. Confidential testing means identifying yourself in some manner to the test site,

with their assurance that this information will remain private. B. Confidential/name based HIV testing involves a person giving their details (name,

age, address) to the clinic doing the test. C. They then have to go back to the clinic after a couple of weeks to get the results. D. The clinics are legally bound to not reveal personal details and test results.

XIII. Mandatory HIV Testing for: A. All blood donations B. Sperm donations C. Organ/tissue donations D. Military recruits E. Peace Corps, Job Corps F. Immigrants applying for permanent residency in the United States G. Federal prisoners H. Newborns

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HIV Testing

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Purpose of HIV Testing • In order for us to stop the spread of

any illness, we need to know if people have it.

• Research has shown that people who know they are HIV positive change their behaviors to reduce the risk of transmission.

• Knowing status is critical to getting medical services.

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Purpose of HIV Testing (cont’d)

• Testing is also done to monitor the pandemic and determine how many people are infected.

• Testing is important in determining the impact of prevention efforts and promoting behavior changes.

• Testing is also critical to protecting the nation’s blood supply.

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Statistics About HIV Testing • As of 2018, Approximately 1.2 million

people in the U.S. have HIV. About 13% of them don't know their status and need testing (U.S. Statistics, 2021).

Why not? • HIV continues to have a disproportionate

impact on certain populations, particularly racial and ethnic minorities and gay, bisexual, and other men who have sex with men (U.S. Statistics, 2021).

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Statistics About HIV Testing (cont’d)

• Most people who are infected with HIV are infected before the age of 25.

• Worldwide, those under the age of 25 account for more than half of all new HIV infections.

• Of those, only 15% know they are HIV positive.

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Most Likely To Test

• Those most likely to test: – African-Americans – People with higher education levels – People who are separated,

divorced or widowed

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Less Likely To Test

• Those less likely to test: – Men – People over age 50 – Those between the ages of 18 and 19 – People with low education level – People in rural areas

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When To Test

• The timing of testing is critical to results.

• Like many infections, HIV has a window period.

• The window period is the time between when a person is initially infected and when the virus will be detectable in a test.

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When To Test (cont’d) • If a person tests for HIV earlier than this,

test results would most likely be negative. • Why? • Because it takes time for the body to

develop antibodies. • Experts believe that it can take anywhere

from 4-12 weeks (and possibly up to 6 months) after initial infection for enough antibodies to be present so that they can be detected in a test.

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Types of HIV Testing  Those that detect antibodies:

 ELISA  Western Blot  IFA  RIPA  Orasure/Oraquick  Home Testing

 Those that detect the genetic material of HIV or identify HIV antigens (viral load):  PCR

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ELISA • The first test licensed to test for the HIV virus

became available in 1985. • The test is called ELISA. • ELISA stands for:

– Enzyme – Linked – Immuno – Sorbent – Assay

• ELISA tests for antibodies for the HIV virus. • It is an indirect test–the presence of antibodies

suggests that HIV is present, but it does not detect the actual virus itself.

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How The Test Works • ELISA is a blood test. • Once a person’s blood is drawn, it is

separated into serum (yellow liquid) and red blood cells.

• The serum is placed in a dish called a Microwell plate.

• The plate has a round bead that has bits of HIV attached to it (HIV antigen). The sample is left for 1 hour.

• If antibodies are present in the blood sample, the bead will recognize the HIV antibodies and attach themselves to the bead.

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Microwell Plate

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How The Test Works (cont’d)

• A chemical is then added to the plate that brings out color (a dark yellow-orange) in any antibodies that are still attached to the bead.

• If color appears, it means that there were HIV antibodies in the person’s serum.

• An HIV negative sample will be unstained and have no color.

References

• U.S. Statistics. (2021, June 2). HIV.Gov. https://www.hiv.gov/hiv-basics/overview/ data-and-trends/statistics

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