Virus Load Testing - Sample Collection


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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