A variety of clinical and imaging parameters have been well validated and standardized for assessment in patients with spondyloarthritis during longitudinal follow-up in clinical practice and research. Outstanding questions were identified by the working group and include further assessment of the most appropriate method for assessment of disease activity and what cutoff is appropriate before access to advanced and costly biologic agents. The Ankylosing Spondylitis Disease Activity Score instrument may have advantages over the Bath Ankylosing Spondylitis Disease Activity Index, but this requires further study. A Bath Ankylosing Spondylitis Disease Activity Index cutoff of 4 has never been validated and also requires further evaluation. It is unclear what constitutes expert opinion for the purposes of defining disease activity. In particular, the role of magnetic resonance imaging requires further investigation.