Page 24 - HIV/AIDS Guidelines

Plasma HIV RNA Testing (Last updated January 10, 2011; last reviewed January 10, 2011)
Plasma HIV RNA (viral load) should be measured in all patients at baseline and on a regular basis thereafter,
especially in patients who are on treatment, because viral load is the most important indicator of response to
antiretroviral therapy (ART) (AI). Analysis of 18 trials that included more than 5,000 participants with viral
load monitoring showed a significant association between a decrease in plasma viremia and improved
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1
clinical outcome. Thus, viral load testing serves as a surrogate marker for treatment response and can be
useful in predicting clinical progression. 3-4 The minimal change in viral load considered to be statistically
significant (2 standard deviations) is a threefold, or a 0.5 log 10 copies/mL change.
Optimal viral suppression is generally defined as a viral load persistently below the level of detection (<20–
75 copies/mL, depending on the assay used). However, isolated “blips” (viral loads transiently detectable at
low levels, typically <400 copies/mL) are not uncommon in successfully treated patients and are not thought
to represent viral replication or to predict virologic failure. In addition, low-level positive viral load results
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(typically <200 copies/mL) appear to be more common with some viral load assays than others, and there is
no definitive evidence that patients with viral loads quantified as <200 copies/mL using these assays are at
increased risk for virologic failure. 6-8 For the purposes of clinical trials the AIDS Clinical Trials Group
(ACTG) currently defines virologic failure as a confirmed viral load >200 copies/mL, which eliminates most
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cases of apparent viremia caused by blips or assay variability. This definition may also be useful in clinical
practice. (See Virologic and Immunologic Failure.)

For most individuals who are adherent to their antiretroviral (ARV) regimens and who do not harbor
resistance mutations to the prescribed drugs, viral suppression is generally achieved in 12–24 weeks, even
though it may take longer in some patients. Recommendations for the frequency of viral load monitoring are
summarized below.

• At Initiation or Change in Therapy. Plasma viral load should be measured before initiation of therapy
and preferably within 2–4 weeks, and not more than 8 weeks, after treatment initiation or after treatment
modification (BI). Repeat viral load measurement should be performed at 4–8-week intervals until the
level falls below the assay’s limit of detection (BIII).

• In Patients Who Have Viral Suppression but Therapy Was Modified Due to Drug Toxicity or
Regimen Simplification. Viral load measurement should be performed within 2–8 weeks after changing
therapy. The purpose of viral load monitoring at this point is to confirm potency of the new regimen (BIII).
• In Patients on a Stable ARV Regimen. Viral load should be repeated every 3–4 months or as clinically
indicated (BII). Some clinicians may extend the interval to every 6 months for adherent patients who
have suppressed viral loads for more than 2–3 years and whose clinical and immunologic status is stable
(BIII).
Monitoring in Patients with Suboptimal Response. In addition to viral load monitoring, a number of
additional factors, such as adherence to prescribed medications, altered pharmacology, or drug interactions,
should be assessed. Patients who fail to achieve viral suppression should undergo resistance testing to aid in
the selection of an alternative regimen, as discussed in Drug Resistance Testing and Virologic and
Immunologic Failure (AI).

References

1. Murray JS, Elashoff MR, Iacono-Connors LC, et al. The use of plasma HIV RNA as a study endpoint in efficacy trials of
antiretroviral drugs. AIDS. 1999;13(7):797-804.
2. Hughes MD, Johnson VA, Hirsch MS, et al. Monitoring plasma HIV-1 RNA levels in addition to CD4+ lymphocyte
count improves assessment of antiretroviral therapeutic response. ACTG 241 Protocol Virology Substudy Team. Ann

Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents C-6

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