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Psoriatic arthritis is a heterogeneous condition with substantial challenges in optimising outcome measures for both clinical trials and daily practice. As with other inflammatory arthritides, there is no gold standard instrument for measuring disease activity or impact, both of which are key to evaluate therapeutic approaches in trials and monitor disease in daily practice. A wide range of domains have been highlighted in the Outcome Measures in Rheumatology (OMERACT) core domain set for psoriatic arthritis; reflecting the disease involvement in multiple tissues (joints, tendons, skin, and spine) and the heterogenous impact of the disease on individuals. This Review summarises the current evidence around outcome measure selection, considering factors such as unidimensional versus multidimensional outcomes, continuous versus binary measures, and the feasibility of these approaches in trials compared with clinical practice.

Introduction C-reactive protein (CRP) is an important non-specific marker of both acute and chronic inflammation and can be elevated in patients with psoriatic arthritis (PsA). However, the use of CRP testing in the management of PsA can vary. This study investigated how CRP testing is implemented in real-world clinical practice for disease management of PsA. Methods A point-in-time survey of rheumatologists and dermatologists and their next six consulting patients with PsA was conducted in France, Germany, Italy, Spain, UK (EU5), and the USA between June and August 2018. Use of CRP testing was obtained by asking the physician to state (yes/no) whether CRP was used to aid PsA diagnosis and/or to monitor the patient’s disease activity. The number of CRP tests conducted in the last 12 months for each patient enrolled was provided. Results Data were collected for 2270 patients (USA, n = 595; EU5, n = 1675). In the EU5, CRP testing was conducted to aid diagnosis in 78.7% of patients (vs. 43.4% in USA) and CRP was used to monitor disease activity in 72.0% (vs. 34.6% in USA). The majority (80.9%) of patients in the EU5 had at least one CRP test in the last 12 months compared to 42.9% in the USA. Patients treated by rheumatologists (vs. dermatologists) were at least 50% more likely to have CRP tested for monitoring purposes, this difference being most pronounced in the USA. In the EU5, CRP testing was conducted a mean ± standard deviation of 2.7 ± 1.7 times during the last 12 months, versus 2.0 ± 1.4 in the USA. Conclusions CRP was more commonly used for the diagnosis and monitoring of PsA in Europe compared to the USA and was more commonly ordered by rheumatologists than dermatologists. In the absence of a better serum biomarker of inflammation, more data are needed to understand how CRP testing should be used in the diagnosis and management PsA.

Objectives: To examine concurrent validity and discrimination of modified minimal disease activity (mMDA) criteria in peripheral spondyloarthritis (pSpA) following OMERACT filter principles and determine predictors of mMDA response. Methods: Four mMDA versions were derived in the ABILITY‐2 study using the SPondyloArthritis Research Consortium of Canada (SPARCC) or Leeds Enthesitis Index (LEI) but excluding psoriasis. To assess concurrent validity, mMDA versions were correlated with Peripheral SpondyloArthritis Response Criteria (PSpARC) remission, Ankylosing Spondylitis Disease Activity Score for inactive disease (ASDAS ID), and physician global. Treatment discrimination was assessed between adalimumab and placebo at week 12. Multiple logistic regression was used to determine baseline predictors of long‐term mMDA responses and sustained mMDA. Results: The four mMDA versions showed a stronger positive correlation with PSpARC remission (rtet>0.95) versus ASDAS ID (rtet>0.75) at week 12 and years 1‐3 and were able to show discrimination (p Conclusions: All four versions of mMDA showed concurrent validity and discriminated well between adalimumab and placebo treatment groups. Early mMDA response is a more consistent predictor of long‐term mMDA achievement than baseline characteristics. The 5 of 6 versions of mMDA could be an appropriate treatment target in pSpA patients.

Background: Many patients with psoriatic arthritis do not reach minimal disease activity (MDA) on methotrexate alone. This phase 4 open-label study aimed to compare attainment of MDA following introduction of adalimumab with methotrexate escalation in patients with psoriatic arthritis who do not reach MDA after an initial methotrexate course (≤15 mg every week). Methods: CONTROL was a phase 4, randomised, two-part, open-label study conducted in 14 countries and 46 sites. We recruited patients with confirmed active psoriatic arthritis, naive to biologic disease-modifying antirheumatic drugs, with an inadequate response to 15 mg or less of methotrexate. In part 1, patients were randomly assigned (1:1) to receive either methotrexate 15 mg (oral or subcutaneous) every week with the addition of adalimumab 40 mg (subcutaneously) every other week (adalimumab plus methotrexate group) or methotrexate (oral or subcutaneous) escalation up to 25 mg every week (escalated methotrexate group). Randomisation was done using Interactive Response Technology and stratified by the duration of methotrexate treatment (≤3 months and >3 months). In this open-label study there was no masking; participants, people giving the interventions, those assessing outcomes, and those analysing the data were aware of group assignment. The primary endpoint was the proportion of patients who reached MDA at 16 weeks. After 16 weeks (part 2), patients who reached MDA (responders) had their current therapy maintained or modified, wheras patients who did not reach MDA (non-responders) had their therapy escalated until 32 weeks. The primary endpoint in part 2 was the proportion of patients who reached MDA at 32 weeks, analysed in all patients who received one or more doses of study drug. The study is registered with ClinicalTrials.gov, NCT02814175. Findings: Between Aug 5, 2016, and March 19, 2020, 245 of 287 patients initially assessed were enrolled in the study (50% men and 50% women; 92% of patients were White). 123 patients were randomly assigned to receive adalimumab plus methotrexate and 122 patients to receive escalated methotrexate. All 245 patients were included in the primary analysis, and 227 completed part 1 and entered part 2. A significantly higher proportion of patients reached MDA at 16 weeks in the adalimumab plus methotrexate group (51 [41%] patients) compared with the escalated methotrexate group (16 [13%] patients; p

Introduction In psoriatic arthritis (PsA), treatment recommendations support first line use of disease-modifying anti-rheumatic drugs (DMARDs). There are few treatment strategy trials and no previous studies have investigated tailored treatment choice by disease severity. Studies in oligoarthritis ( Methods This trial was embedded within the MONITOR-PsA cohort, which uses a Trials Within Cohorts (TWiCs) design. Patients with newly diagnosed psoriatic oligoarthritis, with low disease activity (PASDAS ≤3.2) and the absence of poor prognostic factors (CRP Results Over the 15-month study period, only 1 eligible patient was randomised. Although oligoarthritis patients represented 45% of patients in this early PsA cohort, the majority did not have mild disease (24% raised CRP, 51% moderate disease activity, 13% radiographic damage and/or poor function). Of those meeting trial inclusion criteria, many patients refused treatment in the observational cohort prior to an invitation into the trial as they did not wish to be treated with DMARDs. Conclusion The study was not feasible as designed. Oligoarthritis represents around half of initial PsA presentations, but the majority starting therapy have high impact disease. A small proportion have mild oligoarticular disease but many are not keen on treatment with DMARDs, given the potential side effects of these medications. Further research is needed to support evidence-based treatment in this subgroup.