HOW ARE CHANGES IN VIRAL LOAD MEASURED?

HOW ARE CHANGES IN VIRAL LOAD MEASURED?

Repeat tests of the same blood sample can give results that vary by a factor of 3. This means that a meaningful change would be a drop to less than 1/3 or an increase to more than 3 times the previous test result. For example, a change from 200,000 to 600,000 is within the normal variability of the test. A drop from 50,000 to 10,000 would be significant. The most important change is to reach an undetectable viral load.

Viral load changes are often described as “log” changes. This refers to scientific notation, which uses powers of 10. For example, a 2-log drop is a drop of 102 or 100 times. A drop from60,000 to 600 would be a 2-log drop.
VIRAL LOAD “BLIPS”

Recently, researchers have noticed that the viral load of many patients sometimes went from undetectable to a low level (usually less than 500) and then returned to undetectable. Careful study suggests that these ?blips? do not indicate that the virus is developing resistance.