Defining Outcome Measures for Psoriatic Arthritis: A Report from the GRAPPA-OMERACT Working Group

PsA Updated Core Domain Set

The PsA working group included an international group of rheumatologists, dermatologists, patient research partners (PRP), methodologists, and 2 fellows. The working group developed a plan to update the 2006 PsA Core Domain Set³ following the OMERACT meeting in May 2014⁴. At the meeting, OMERACT participants voted that the PsA core domain set should be revised because of the updated knowledge about PsA (including the importance of individual disease manifestations), the need to incorporate patient input, and the new OMERACT “Filter 2.0” methodology (a set of guidelines proposed by OMERACT for development of core domain sets)⁵. The group developed a plan to address these issues through individual work streams that culminated in a series of consensus activities. PRP were included in all phases including 1 PRP on the steering committee, and at least 1 PRP was involved in the planning and interpretation of each of the work streams^6,7.

Using the OMERACT Filter 2.0 framework, the working group performed an update (2010–2015) of the systematic literature review of domains measured in RCT and LOS⁸. Next, patient domains were identified through international focus groups (130 patients in 7 countries). A total of 39 domains were identified from focus groups and literature review. In a phone conference, the working group discussed how to organize and describe these 39 domains in patients’ words. Patient and provider Delphi surveys were then sent to 75 patients and 125 physicians (rheumatologists and dermatologists) to rate the importance of the items for measurement in RCT and LOS. These data formed the basis for a group discussion at a Nominal Group Technique meeting held in Jersey City, New Jersey, USA, in March 2016. Twelve PRP and 12 physicians came to a consensus on a preliminary core domain set through a moderated discussion. The preliminary core domain set was then proposed at the OMERACT meeting in Whistler, British Columbia, Canada, in May 2016. The final core domain set (Figure 1) included 3 parts: an inner circle (should be measured in all RCT and LOS), a middle circle (important, but not mandatory), and the outer circle that represents the research agenda. The inner circle includes musculoskeletal (MSK) disease activity (peripheral arthritis, enthesitis, dactylitis, and spine symptoms), skin disease activity (skin psoriasis and nail dystrophy), pain, patient’s global assessment, physical function, health-related quality of life, fatigue, and systemic inflammation. The middle circle included economic cost, emotional well-being, participation, and structural damage. Finally, stiffness, independence, treatment burden, and sleep were included in the research agenda. Some domains included in the 2016 core domain set were also present in the 2006 and 2014 Core Domain Sets, some moved from the outer circle, and others were added (Figure 1 shows these changes).

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Figure 1.

The 2006 and 2016 GRAPPA-OMERACT PsA Core Domain Sets. Adapted from Orbai, et al. Ann Rheum Dis 2016 Sep 9 (E-pub ahead of print); with permission. * In the 2016 core domain set (right), domains that moved from 1 of the outer circles to either the middle or inner circle. ^† MSK disease activity (now includes peripheral arthritis, enthesitis, dactylitis, and spine symptoms) and skin disease activity (psoriasis and nail dystrophy) were redefined. ^‡ New additions to the set. GRAPPA: Group for Research and Assessment of Psoriasis and Psoriatic Arthritis; OMERACT: Outcome Measures in Rheumatology; PsA: psoriatic arthritis; MSK: musculoskeletal; MRI: magnetic resonance imaging; CT: computed tomography; US: ultrasound; PGA: physician’s global assessment; HRQoL: health-related quality of life.

Having achieved ratification of the core domain set, the next step for the PsA working group is to select outcome measurement instruments. One of the issues raised at OMERACT and again at the GRAPPA meeting was the number of domains included within the core domain set. Identifying the full set even within the inner circle is a daunting task. It is important to recognize that each domain will not necessarily need to be measured by an individual instrument. Most recent RCT are already measuring these domains⁸. In fact, among the 8 most recently conducted RCT, most of these domains were identified, although fatigue, participation, and spine symptoms are less commonly measured (Table 1).

PsA Core Set Working Group Meeting

During this meeting, the working group discussed and reviewed the organization of work streams to tackle the development of the PsA Core Outcome Measurement Set (Figure 2). Each work stream included at least 2 PRP. A series of systematic literature reviews are ongoing to assess measurement properties of candidate instruments, including patient-reported outcomes assessing skin and joint disease activity, fatigue, pain, patient’s global assessment, health-related quality of life, participation, and emotional well-being; physical examination methods for assessing MSK and skin disease activity; systemic inflammation; imaging modalities to assess structural damage and disease activity; and composite disease activity measures. A qualitative assessment of the feasibility and the content validity of available instruments from the perspective of patients and physicians has been launched. Simultaneously, instrument assessments are being performed within RCT and LOS. These 3 efforts will produce data about the measurement performance of each instrument. These data will be presented and discussed in a workshop and breakout groups at the next GRAPPA annual meeting, after which the group may realize that additional data are needed. The working group will then refine the data obtained and structure patient and physician Delphi surveys using methods similar to those used in the development of the core domain set. The patient and physician Delphis will be used to achieve consensus on the optimal instruments to address some, if not all, of the core domains. If needed, an in-person consensus meeting will be held following the Delphi. The working group aims to present a preliminary core outcome measurement set for discussion and voting at the next OMERACT meeting in May 2018.

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Figure 2.

Road map for developing the PsA Core Outcome Measurement Set. Work streams are listed in chronological order. PsA: psoriatic arthritis; SLR: systematic literature review; OMI: outcome measurement instruments; RCT: randomized controlled trials; LOS: longitudinal observational studies; WG: working group; GRAPPA: Group for Research and Assessment of Psoriasis and Psoriatic Arthritis; OMERACT: Outcome Measures in Rheumatology.