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It is believed that many people who are HIV infected in
the United States have not been tested, and are unaware of
their HIV-positive status. Many of these people may unknowingly
pass HIV infection on to others. Many who are HIV positive
do not realize that they are infected with HIV until they
present with symptoms of infection. Since most people don't
have symptoms for years, they do not find out their HIV status
until later in the disease progression. By the time they find
out they are infected, they have missed opportunities to take
care of their health and avoid passing the infection on to
others.
It is important for anyone at risk of HIV infection to get
tested. Those who are uninfected can learn to take steps to
avoid infection and those who are infected can take steps
to take care of their own health as well as to avoid passing
the infection on to others.
HIV antibody testing has been available since 1985. There
are several approved tests that are available to detect HIV
antibodies. These tests determine HIV infection by detecting
the presence of HIV antibodies produced by the immune system.
The Food and Drug Administration (FDA) has approved several
HIV antibody tests. These tests have a 2-step process of a
screening test and when the screening test is reactive, a
confirmatory test.
Step 1. Screening Test. The first test done on
a specimen is a screening test called an Enzyme Linked
Immunosorbent Assay (ELISA, also called EIA). This test
screens for the presence of antibodies to HIV in blood,
urine, or oral fluid. Screening tests are inexpensive tests
that are highly accurate.
Most HIV antibody screening tests are conventional screening
tests in that the specimen is collected from the client
and sent to a laboratory for testing. If a screening test
is negative (no antibodies were detected), the results can
be given to the client. If the screening test is reactive
at the laboratory, the additional confirmatory Western Blot
is conducted on the same sample.
Rapid tests are also screening tests. However, rapid screening
tests are conducted at the test site, often with the client
present and negative results are available in under an hour.
Reactive results, wherein antibodies were detected, must
be confirmed by an additional test. This is because there
is a small chance that an HIV screening test may detect
proteins related to other autoimmune diseases and react
to these proteins with a positive result.
Step 2. Confirmatory Testing If a rapid test is
reactive, an additional specimen must be drawn from the
client and sent to the lab for confirmatory Western Blot
testing.
It is possible for someone who is NOT infected with HIV
to test reactive on a screening test because the test detected
something other than HIV. For this reason, it is critical
that reactive screening tests are verified with a confirmatory
test and that clients are NOT told they are infected with
HIV Unless confirmatory test verifies that HIV antibodies
are present.
When a person has a reactive (positive) screening test,
a confirmatory test, called the Western Blot test is done
to verify the presence of HIV antibodies. The HIV Western
Blot detects antibodies to individual proteins that make
up HIV. This test is much more specific and more costly
than the ELISA screening test.
Different Antibody Testing Specimen
Options
HIV antibody tests are designed to detect HIV antibodies
in blood, urine, or oral fluid (oral mucosa transudate) samples.
Blood
The most frequently used HIV antibody test is the blood-based
test. This test detects HIV antibodies in the blood. Depending
on the test type, blood from a venipuncture or fingerstick
will be used. This is the test that is used most often in
public health clinics and doctors' offices. Most rapid screening
tests use fingerstick blood.
As with all screening tests, reactive blood fluid screening
tests must be confirmed with a Western Blot test. For most
HIV testing, this confirmatory testing is done on the same
sample in the laboratory. For reactive rapid tests, an additional
sample needs to be drawn and sent to the lab for the confirmatory
Western Blot.
Oral Fluid
This test detects HIV antibodies in the mucous membrane of
the mouth, called oral mucosal transudate. The oral test kit
uses a special collection device that looks like a toothbrush.
No needles are necessary. There are some rapid tests that
use oral fluids. Many public health clinics also offer oral
fluid testing. Some provide rapid oral fluid testing. As with
all screening tests, positive oral fluid screening tests must
be confirmed with a Western Blot test.
It is important to note that, even though antibodies to HIV
can be found in saliva and oral fluids, these fluids do not
contain sufficient amount of the virus to be infectious and
therefore, are not considered a risk for transmitting the
virus.
The HIV virus is the disease. The virus causes infection.
Antibodies are the immune system's response to the disease.
Antibodies do not cause disease, they fight the infection.
Urine
A urine-based test for HIV antibodies is available for use
only in physicians' offices or medical clinics. It tests for
HIV antibodies in the urine. It is important to note that,
even though antibodies to HIV can be found in urine; urine
is not considered a risk for transmitting the virus. As with
all screening tests, a positive urine HIV screening test must
be confirmed with a Western Blot test, which can be done on
the same specimen.
Rapid HIV Test
The rapid HIV test is a screening test that can provide results
in less than an hour. Rapid testing can be conducted on either
blood and/or oral mucosal transudate, depending on the type
of rapid test. As with all screening tests, any reactive positive
rapid test must be confirmed with a conventional Western Blot
test.
Home HIV Test Kits
Currently, the only licensed and FDA-approved test kit for
home HIV antibody testing is the "Home Access HIV-1 Test System"
manufactured by Home Access Health corporation. If you are
unsure if an HIV test is FDA approved, you can check on the
FDA website for approved HIV tests: http://www.fda.gov/cber/products/testkits.htm.
The test requires a few drops of blood, which is then mailed
to the company in a safe mailer. If the screening test is
reactive, a confirmatory western Blot test is done by the
same laboratory so that final results are available to clients.
The client calls the company to learn their results over the
phone.
Internet Test Kits
Although other "home test" kits may be ordered over the internet,
they may not be approved by the FDA. They are not guaranteed
to be accurate. It is not recommended to use any test which
has not been approved by the FDA.
Other Tests for HIV
The p24 antigen test is a blood test measures a core
protein of HIV. This protein occurs during primary infection
(the first few weeks of infection) but may disappear as soon
as antibodies to the virus are present. Because of this, and
because of the expense of the test, p24 antigen tests are
currently only available in specific circumstances.
The plasma HIV RNA or proviral DNA test are blood
tests that may be run in people with suspected new HIV infection.
They are expensive and not used as screening tests for the
general public. However, anyone who has had a potential exposure
to HIV through unprotected sex or sharing needles, and who
presents with symptoms of primary infection (usually seen
within the first two weeks of infection with HIV) should ask
their medical practitioner if this test is advisable. Primary
infection is discussed later in this course.
HIV viral load test measures the amount of HIV in
an infected person's bloodstream. It is rarely used to diagnose
HIV infection. It is most often used in individuals who are
HIV-positive to measure the effectiveness of antiretroviral
medications used to treat HIV infection.
Confidential HIV Testing
A confidential HIV test means the patient gives their real
name, and the information about their testing is maintained
in medical records. Their results are confidential. Results
and testing information are not released to others except
when medically necessary or under special circumstances including
when they sign a release for the results to be given to another
person or agency.
HIV is a reportable condition. Confidential HIV results are
reported to local public health officials. The Legal section
of this course further addresses HIV reporting.
Continue on to Testing for
HIV, Con't.
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