Amplification assays (-PCR, DNA PCR, and b DNA tests) are routinely used to detect viral RNA in clinical specimens. The tests can be quantitative when reference standards are used, and appropriate positive and negative controls must be included in each test. Because these molecular based tests are very sensitive, they form the basis for plasma viral load determinations. It is generally agreed that the amount of HIV in the blood (viral load) is of significant prognostic value. There are continual rounds of viral replication and cell killing in each patient, and the steady-state level of virus in the blood varies with individuals. A single measurement of plasma viral load approximately 6 months after infection can predict the risk of development of AIDS in men several years later. In women, viral load appears to be less predictive. The plasma viral load appears to be the best predictor of long-term clinical outcome, whereas CD4 lymphocyte counts are the best predictor of sho-term risk of developing an oppounistic disease. Plasma viral load measurements are a critical element in assessing the effectiveness of antiretroviral drug therapy. Ref:- Baveja textbook of Microbiology