surrogate marker

surrogate marker – A surrogate marker is when something that is easy to measure is used as a marker for something that is difficult to measure directly.

The CD4 count doesn’t directly measure HIV. But it is a good surrogate (or indirect) marker for how HIV has damaged your immune system. It is closely linked to the┬árisk of HIV-related complications.

Viral load in blood is a good surrogate marker for levels of HIV in your body overall including in other body sites.