Article Text

Extended report
A psychometric analysis of outcome measures in peripheral spondyloarthritis
  1. Maureen C Turina1,
  2. Sofia Ramiro1,
  3. Dominique L Baeten1,
  4. Philip Mease2,
  5. Jacqueline E Paramarta1,
  6. In-Ho Song3,
  7. Aileen L Pangan3,
  8. Robert Landewé1
  1. 1Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology and immunology Center, Academic Medical Center/University of Amsterdam, Amsterdam, The Netherlands
  2. 2Swedish Medical Center & University of Washington, Seattle, Washington, USA
  3. 3AbbVie Inc., North Chicago, Illinois, USA
  1. Correspondence to Professor Robert Landewé, Department of Clinical Immunology and Rheumatology, Amsterdam Rheumatology and immunology Center, Academic Medical Center/University of Amsterdam, Meibergdreef 9, Amsterdam 1105AZ, The Netherlands; landewe{at}rlandewe.nl

Abstract

Objectives To assess the discriminatory capacity of various outcome measures and response criteria in patients with peripheral spondyloarthritis (pSpA).

Methods Data originated from two randomised controlled trials, ABILITY-2 and Tnf Inhibition in PEripheral SpondyloArthritis (TIPES). Continuous outcome measures included patient's global assessment (PGA)/physician's global assessment of disease (PhGA), C-reactive protein (CRP), tender joint counts (TJC)/swollen joint counts (SJC), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and the Ankylosing Spondylitis Disease Activity Score (ASDAS). Dichotomous response criteria included Peripheral SpondyloArthritis Response Criteria (PSpARC), American College of Rheumatology (ACR), ASDAS and BASDAI response criteria. The capacity to discriminate between adalimumab and placebo groups was assessed by standardised mean differences (SMD) for continuous variables, and Pearson's χ2 for dichotomous response criteria.

Results Within each trial, the composite indices for axial SpA assessment, ASDAS-CRP (SMD: −0.63 and −0.89 in ABILITY-2 and the TIPES trial, respectively) and BASDAI (SMD: −0.50 and −0.73), and the single-item measures PGA (SMD: −0.47 and −1.12) and PhGA (SMD: −0.64 and −0.87) performed better than other single-item measures, such as CRP (SMD: −0.18 and −0.53), SJC or TJC. In general, the PSpARC and ACR response criteria discriminated better than ASDAS and BASDAI response criteria.

Conclusions The axial SpA-specific ASDAS-CRP and BASDAI, but also PGA and PhGA, demonstrated good discriminatory ability in patients with pSpA. The pSpA-specific pSpARC response criteria and the rheumatoid arthritis-specific ACR response criteria also discriminated well. To fully capture typical pSpA manifestations, it may be worth developing new pSpA-specific indices with better performance and face validity.

Trial registration numbers ABILITY-2: NCT01064856; TIPES: EUDRACT 2008-006885-27.

  • Anti-TNF
  • Spondyloarthritis
  • Outcomes research
  • Disease Activity
  • Patient perspective

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