In clinical trials the DAS28 can be used to assess whether an individual patient has a significant improvement of the disease activity, compared to baseline. For this aim, the EULAR response criteria can be used. These criteria are explained in detail here.
It is also possible to choose a baseline independent absolute level of disease activity as goal for your therapeutic intervention. A DAS28 value of 3.2 (low disease activity) or even 2.6 (remission) can be selected as threshold.