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This test
detects acute infection prior to seroconversion.
The
PCR tests is approved
by the FDA only for people with established AIDS and taking
medications but has become popular also as a
diagnostic tool.
Because of this FDA
specification
we always associate a free HIV ELISA antibodies.
Earlier diagnosis leads to earlier referral for appropriate
care and preservation of health.
If the
test is negative the person is almost 100% sure
to be negative for the presence of HIV1 viruses.
A
recent study
has shown that this test is able to detect the
presence of HIV virus 6 to 42 days prior to a
positive HIV-ELISA antibodies test and is
conclusive 28 days from exposure.
HIV - PCR
stands for
HIV- Polymerase
Chain Reaction
and is
also known as
Viral
Load
testing
because it looks for the
presence of the Immuno Deficiency Virus in your blood. Contrary to the HIV-Elisa Antibodies test
the HIV-PCR is the direct measurement of
the amount of
HIV particles present in the blood. The
Polymerase Chain Reaction (PCR) technology amplifies even
the smallest amount of Virus particle millions of time, and since this test identifies and
measures the genetic material (rDNA) resulting from the virus infection, is
also known as Nucleic Acid test.
Watch
video of inventor of PCR methodology
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The
HIV PCR (also called Viral Load) is one of the preferred HIV
tests because it significantly increases the detection of new cases
of HIV infection. In fact this test detects acute infection
prior to seroconversion which means prior of one being positive on
an antibodies test (ELISA).
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HIV - PCR
stands for
HIV- Polymerase
Chain Reaction
and is
also known as Viral
Load
testing
because it looks for the
presence of the Immuno Deficiency Virus in your blood.
Contrary to the HIV-Elisa Antibodies test
the HIV-PCR is the direct measurement of
the amount of
HIV particles present in the blood.
The
Polymerase Chain Reaction (PCR) technology amplifies even
the smallest amount of Virus particle millions of time, and since this test identifies and
measures the genetic material (rDNA) resulting from the virus infection, is
also known as Nucleic Acid test. |
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If the test is
negative it may be considered conclusive
28 days from exposure.
A
recent study
has shown that this test is able to detect the presence of HIV 6 to 42 days prior to
the appearance of antibodies in your blood (positive HIV-ELISA).
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Earlier diagnosis
leads to earlier referral for appropriate care and preservation of
health.
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Increased
awareness of infection status combined with appropriate preventive
counseling may significantly reduce the unknowing spread of
infection.
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Two Studies
published in the New England Journal of Medicine analyzed the
cost-effectiveness of HIV screening. Both used different models but
reached the same conclusions "routine Screening is justified,
beneficial, and cost-effective."
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Several studies
have suggested that individuals with primary infection may he
significant contributors to the spread of HIV. These individuals
have very high HIV viral load in blood and semen, are extremely
infectious, and are usually unaware of their HIV status.
In acute HIV infection and prior to seroconversion
the viral burden is very high (10 to >1.000.000 copies/mL).
The period
after infection with HIV
but before the
development of detectable antibodies is a period of active HIV
replication and transient immune suppression. The number of HIV
viruses rises rapidly in the plasma, often reaching levels in excess
of 1 million copies per milliliter, with widespread dissemination
into lymphoid organs throughout the body.
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By identifying
highly contagious individuals, this test provides a public health
targeting opportunity for HIV prevention. |
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Although the majority of people
are symptomatic with an illness resembling infectious mononucleosis or
influenza and a large percentage of these patients present for care at
health care facilities with "acute retroviral syndrome" (ARS),
some people
have no clinical symptoms.
- The HIV PCR
sensitivity limit per individual sample is approximately 50-2000
copies/mL according to the different methodologies used. .
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The
PCR tests is
approved by the FDA only for people with AIDS and taking medications but
has become popular also as a diagnostic tool. That is the reason why we
associate a free HIV ELISA antibodies with his test to be taken 4 months
after the PCR test.
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The test may be
falsely negative in people with HIV if the infection is so recent (less
than 28 days old) that virus has not yet begun to produce detectable
quantities of itself, or if a person is controlling the infection
spontaneously or using the newly potent anti-retroviral
medications and has brought the infection under control.
- Evidence
shows that keeping the viral load levels as low as possible for as long
as possible decreases the complications of HIV disease and prolongs
life.
- Public
health guidelines state that treatment should be considered for
asymptomatic
HIV-infected people who have viral
loads higher than 30,000 copies per milliliter of blood using a test
known as a branched DNA test, or more than 55,000 copies using an RT-PCR
test
which is the test we use (Amplicor).
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Measurement of plasma HIV-1
RNA levels (virus load) can be used to monitor the course of disease and
the response to antiretroviral therapy in patients with HIV-1-infection.
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What follows is a table with
assays based on the different methods that have been developed for
quantifying plasma
HIV-1 RNA.
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These include
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Methodology |
Name |
Manufacturer |
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Reverse transcription followed by polymerase chain reaction (RT-PCR)
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Amplicor
HIV-1 Monitor
(the one we
use) |
Roche Diagnostic Systems |
Nucleic acid sequence-based amplification NASBA;
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HIV-1 RNA QT |
Organon-Teknika |
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Nucleic
acid hybridization and branched DNA (bDNA) signal
amplification |
Quantiplex
HIV-1 RNA |
Bayer Nucleic Acid Diagnostics. |
DNA
hybridization
and colorimetric detection
not widely available at this time. |
Digene Assay |
Digene
Diagnostics |
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Amplicor
HIV-1 Monitor |
In PCR-based
assays, HIV RNA is converted into DNA by reverse transcription
followed by PCR amplification of the DNA. The PCR product is
detected by hybridization with an enzyme-conjugated probe
specific for HIV-1, and quantified by reacting bound probe with
a substrate that undergoes a color change, as in an ELISA.
At present the Roche Amplicor HIV-1 Monitor (RT-PCR) assay is
the only one approved by the U.S. Food and Drug Administration,
and is the most widely used in clinical practice. |
Quantiplex
HIV-1
RNA |
The branched
DNA assay uses non-enzymatic means to amplify the signal from
HIV RNA. In this assay, viral RNA is "captured" by hybridization
to complementary oligonucleotides that are bound to the wells of
a microtiter plate. The captured viral RNA target is then
hybridized to branched oligonucleotides (hence the name
"branched" DNA assay), which in turn are hybridized to
enzyme-conjugated oligonucleotides that can be quantified as
above. |
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HIV-1
RNA QT |
The NASBA
assay is similar in concept to the RT-PCR assay except that
reactions occur at one temperature. |
Results of the three
commercially available quantitative HIV-1 RNA assays are highly
correlated but not interchangeable so it is important that the
same method be used each time.
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All three
assays have a lower limit of quantification of approximately 50-80
copies/mL
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Although
the lower limit of the standard Amplicor HIV-1 Monitor assay is 400
copies/mL, the range of the assay can be extended, a modification
commonly referred to as the "ultrasensitive" HIV-1 Monitor assay.
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These
assays are much less precise at plasma HIV-1 RNA titers below 200
copies/mL
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Although
most strains of HIV-1 that circulate in North America belong to
subtype B, more than 10 different subtypes are found around the
world. The HIV-1 Monitor 1.0 (RT-PCR) assay is significantly less
sensitive for detecting HIV-1 from subtypes A, E, and F as compared
to the Quantiplex version 3.0 (bDNA) assay.
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Plasma
HIV-1 RNA levels that appear to be lower than expected in a patient
with advanced disease can be a clue to infection with a non-subtype
B strain. Incorporation of alternative primer sets in the new
version of the HIV-1 Monitor assay (version 1.5) has improved the
ability of this assay to diverse HIV-1 subtypes.
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