The viral load test may be a better indicator of disease progression than the T-helper-cell count, and it may indicate disease progression more quickly. This test can also be used to determine whether or not medication changes have been effective. For instance, with the initiation of a new medication, one would hope to see a rise in the T-helper-cell count and a decrease in the viral load. It is assumed that when the viral load is low (and therefore the amount of circulating virus is low) disease progression has been slowed.
The T-helper-cell count and viral load are usually checked every three to six months or so, or about three to four weeks after every change in the dose or type of antiretroviral medication or protease inhibitors. It is not recommended that the viral load be checked for up to one month following a viral or bacterial illness or after a vaccination, since these situations can temporarily raise the viral load. In addition, there are some slight differences among the tests, so the same viral load test should always be used for the same person.