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Virus
Load Testing
Sample
Collection
Blood for plasma HIV-1 RNA testing should be collected into tubes
containing EDTA as an anticoagulant, and the plasma separated and
stored frozen at -70o C until testing. Studies show that HIV-1 RNA
is stable for up to 48 hours at room temperature in the presence
of EDTA, but ideally samples should be processed within 6 hours
after collection (61; 62).
Events leading to immune activation such as vaccination or acute
infectious illness can transiently raise the plasma HIV-1 RNA level
(63; 64).
Therefore, plasma HIV-1 RNA testing should not be performed within
four weeks of an intercurrent infection or immunization. Because
of differences between assay formats and commercial laboratories,
the same laboratory should be used for serial tests on an individual
patient.
Current treatment
guidelines recommend obtaining two measurements of plasma HIV-1
RNA to determine the baseline or "set-point" virus load
(65). Virus load testing should be performed
immediately prior to initiating treatment and repeated within 2-8
weeks of starting treatment in order to assess the initial response
to a regimen. A 1.0-log10 decline in plasma HIV-1 RNA level is expected
for treatment-naïve patients within 8 weeks of starting an
initial antiretroviral regimen, and plasma virus should fall to
undetectable levels (below 50 copies/mL) by 16 weeks.
However, more than 24 weeks may be required for plasma virus titers
to fall below the limit of detection in patients with high pre-treatment
levels of viremia (above 100,000 copies/mL). Declines of 0.5-log10
or more within 8 weeks should be expected following a change in
regimen due to treatment failure. Subsequently, plasma HIV-1 RNA
levels should be repeated every 3-4 months in order to monitor the
success of antiretroviral therapy.
4/15/01
Copyright 2001
by HIV and Hepatitis.com. All Rights Reserved
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