RNA Assay Plasma HIV RNA determination has become an important marker in the evaluation and management of HIV disease. Viral burden or load refers to a quantitative measure of HIV viral RNA in the peripheral circulation, or level of virus in the blood. Viral load can provide significant information about predicting the course of disease progression, when to initiate antiretroviral therapy, the degree of antiretroviral effect achieved and the failure of a drug regimen. Plasma RNA levels fall dramatically following effective antiretroviral therapy. Determinations of quantitative HIV RNA levels in plasma do not detect viral RNA sequestered in lymphoid or other tissues.
Viral load is an indication of the net level.
Viral load and CD4 cell counts are distinct markers which provide different information. Each is an independent predictor of clinical outcome, and used in combination they can give a more complete indication of clinical status, treatment response, and prognosis. Generally, high viral load indicates higher risk for disease progression, and lower levels, less risk. A metaphor used by John Coffin, PhD from Tufts University, at the XI International Conference on AIDS described the asymptomatic, infected patient as a train rushing along the track, headed for a bridge that had been destroyed. A baseline determination of viral burden is recommended, with subsequent measurements every 1-3 months, in conjunction with CD4 cell monitoring and clinical evaluation such as history and physical exam.