Date: Monday, October 22, 2018
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose: A psoriatic arthritis (PsA) core domain set to be measured in randomized controlled trials (RCT) and longitudinal observational studies (LOS) was developed by Group for Research and Assessment of Psoriasis and PsA (GRAPPA) and endorsed by Outcome Measures in Rheumatology (OMERACT) in 2016. Joint counts are central to the measurement of musculoskeletal (MSK) disease activity, one of the key domains. Having reviewed the 28 as well as 76/78 joint counts, the 66/68-swollen and tender joint count (SJC66/TJC68) was identified as the target instrument for peripheral joint assessment. We assessed the domain match, feasibility, construct validity, reliability, responsiveness, discrimination and thresholds of meaning of SJC66/TJC68 in PsA to secure endorsement of this instrument for inclusion in the PsA Core Outcome Measurement Set at OMERACT.
Methods: A multi-prong protocol was designed to assess the properties of the joint counts. A provider and methodologist focus group at GRAPPA, an international web-based working group survey, and patient research partner survey and web-based focus groups were conducted to assess domain match and feasibility. To address reliability, construct validity, responsiveness and discrimination, we conducted a systematic literature review and analyzed data from one LOS and 8 PsA RCTs using a standardized protocol. These results were summarized in a “Summary of Measurement Properties Table,” (developed by OMERACT), and presented and discussed at OMERACT2018. OMERACT participants voted on endorsement of the SJC66/TJC68 as an instrument for the PsA Core Outcome Measurement Set.
Results: Participants in the preconference work and within our working group agreed that the SJC66/TJC68 joint count matched the domain “MSK disease activity: peripheral arthritis” and is feasible for use in RCT and LOS. Construct validity was demonstrated in four published studies and within our primary data analyses. Test-retest reliability was only examined in one cohort of 14 patients with PsA but was found to be excellent (0.8-0.9). Inter-rater reliability has been previously shown to be low for the SJC66 (intraclass correlation [ICC], 0.24) but good for the TJC68 (ICC, 0.78). The SJC66/TJC68 was responsive and able to discriminate between patients receiving placebo and active treatment. Finally, the minimally important difference was found to be 2.5 joints for both SJC66 and TJC68 in a new analysis of an LOS. Overall, 17 (100%) of patient research partners and 96/113 (85%) of other stakeholders (eg, clinicians, methodologists) voted for full endorsement of the SJC66/TJC68.
Conclusion: SJC66/TJC68 is a feasible, valid and reliable instrument for the measurement of peripheral joint activity in RCT/LOS and is recommended over the 76/78 and 28 joint counts. The SJC66/TJC68 is the first fully endorsed instrument within the PsA Core Outcome Measurement Set.
To cite this abstract in AMA style:Duarte-Garcia A, Eder L, Goel N, Christensen R, de Wit M, FitzGerald O, Gladman DD, Holland R, Leung YY, Lindsay C, McHugh N, Mease PJ, Orbai AM, Shea B, Strand V, Tillett W, Coates LC, Ogdie A. The 66/68 Joint Count for the Measurement of MSK Disease Activity/Peripheral Joint Activity in Psa: A Grappa-Omeract Working Group Initiative [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 10). https://acrabstracts.org/abstract/the-66-68-joint-count-for-the-measurement-of-msk-disease-activity-peripheral-joint-activity-in-psa-a-grappa-omeract-working-group-initiative/. Accessed August 11, 2020.
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