Viral load tests are now being used to help doctors determine what treatments are best for HIV positive individuals and whether or not they are working effectively. Viral load is reported as the number of RNA copies / mL of blood plasma.
A result below 10,000 to 20,000 copies per mL is generally considered low, while 50,000 copies / mL and above is considered high.
If viral load drops more than five fold during the treatment, the therapy is considered to be working. If, however, viral load decreases less than five fold, or increases during treatment, the doctor and the HIV positive individual may decide to switch to a different treatment. (A 10 fold change is equivalent to a 1 log variation, so a five fold change is equivalent to a 0.7 log variation).
Before deciding on the treatment regime, factors such as general health, CD4 cell count, previous therapies, etc must be taken into consideration. Drugs may not be working for a number of different reasons including resistance to anti-HIV drugs, inadequate dose or non-adherence to therapy.
Several studies (SPICE (5),CHEESE(6) and HAART(7)) have shown that changes in viral load and CD4 count, brought about by treatment, correspond to clinical outcome. The greater the reduction in viral load the greater the improvements in clinical outcome. Viral load and CD4 can also predict the likelihood of disease progression, including death.
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