This is a prospective, multicentre, phase IV trial assessing the value of the ultrasound scores PsASon22 and PsASon13 in differentiating between clinically active and inactive patients with psoriatic arthritis, following a treatment with Apremilast for up to 24 months. Additionally, convergent construct validity, inter/intra-reader reliability, sensitivity to change and differences in change in certain patients will be tested for the ultrasound scores.
The main purpose of this study is to validate the ultrasound scores PsASon22 and PsASon13 in patients with active psoriatic arthritis undergoing a treatment with Apremilast.