Table 3.

Summary of core domain discussion during PsA workshop breakout groups at OMERACT 2016

Domain	Support inclusion	Challenges	Suggestions
Structural damage	Important aspect of medication efficacy for PsA. Keep a special status in the middle core with requirement to be measured at least once during the development program of a new drug for PsA.	Not feasible to require in all RCTs. Small changes if any (no responsiveness) in short clinical trials.	Combining modalities of assessment is important. Measurement instruments may concomitantly assess damage, inflammation and disease activity
Systemic inflammation	Important, majority in all groups supported inclusion. Also very important in longitudinal studies due to link with heart disease and potentially other comorbidities.	-	When considering instruments also consider imaging for this domain
Emotional well-being	Very important to patients: important in qualitative research and patient surveys. Psychological distress is frequent in both psoriasis and psoriatic arthritis. Together with participation and fatigue an appropriate replacement for HRQoL.	Feasibility concern and concern over necessity in every RCT. Multifactorial concept potentially overlapping with patient global and fatigue. How is it different from HRQoL? This could be an important/key contextual factor.	We need to better understand overlap with patient global and HRQoL. We also need to find instruments for assessment. Emotional well-being should be examined as a contextual factor.
MSK disease activity	Majority agreement with the updated comprehensive MSK disease activity. Easily comprehensible as a domain even for non- rheumatologists.	Inclusion of spine symptoms within MSK disease activity is challenging due to the lack of good instruments to assess activity; additionally, measuring spine symptoms in all trials is not currently feasible. Some preferred the individual components be considered instead of the broader domain of MSK disease activity.
Participation	Face validity: important to patients and physicians, shows ability to “live one’s life”. A common discussion point was that participation is really at the core of why we treat patients: to improve their function in their daily lives. Participation can be measured and it is responsive. Work and employment are very important for patients. This is distinct from physical function. However, this is also more than just work and includes social and leisure activities.	The definition as proposed is broad. There was a concern for overlap with HRQoL and physical function, and it may be influenced by emotional well-being. Concern for redundancy if also including HRQoL in inner core. Some thought it should be one or the other.	Include in the inner core and move HRQoL in the middle circle. Study the independent contribution of the domain in explaining PsA variability; and overlap with other domains.
Skin disease activity	Majority agreement, important to patients and physicians	Some concerned about feasibility of measuring in all RCTs
Patient global assessment	Always measured	Problematic to pinpoint the exact concept behind this domain	The patient global needs to be addressed among all diseases and should be further studied.
Physician global	N/A	Felt to be captured in MSK disease activity. Potentially subject to bias.
Proposed core set	Felt to be comprehensive. A strength is that most of these domains are already measured in clinical trials.	Some participants felt the core set contained too many domains, potentially limiting feasibility. There was a concern for responder burden at the measurement stage.	Examine PROMIS measures Examine redundancies among domains.