Are patient-reported outcome instruments for ankylosing spondylitis fit for purpose for the axial spondyloarthritis patient? A qualitative and psychometric analysis

Rheumatology (Oxford). 2015 Oct;54(10):1842-51. doi: 10.1093/rheumatology/kev125. Epub 2015 May 21.


Objectives: Several patient-reported outcome (PRO) instruments have been validated in AS. This study aims to evaluate several measurement properties of such PROs in a broad axial SpA (axSpA) population, including both AS and non-radiographic axSpA (nr-axSpA) subpopulations.

Methods: PROs assessed were total and nocturnal back pain, patient global assessment of disease activity, BASDAI, BASFI and the 36-item Short Form Health Survey. A literature review and both clinician and patient qualitative interviews provided information on instrument content validity. Reliability (test-retest and internal consistency), construct validity (PROs, clinical-outcome correlations and known-groups validity) and PRO responsiveness were assessed. Data from the RAPID-axSpA trial (NCT01087762) investigating certolizumab pegol efficacy in axSpA, including relevant subpopulations, were utilized.

Results: Concepts identified for the broad axSpA population by both clinician and patient interviews were consistent with those identified through literature review of AS. All PROs demonstrated reliability in the RAPID-axSpA population (n = 325), with test-retest intraclass correlation coefficients and internal consistency Cronbach's α >0.8. Validity was supported by agreement between PROs and clinician-rated measures; except for the 36-item Short Form Health Survey Mental Components Summary, correlations between PROs and physician global assessment of disease activity ranged from 0.28 to 0.42 for week 0 and from 0.53 to 0.65 for week 24. PRO measures showed good sensitivity to change (effect size >0.8) at weeks 12 and 24 for responders. No variations in measurement properties were noted between the subpopulations.

Conclusion: This study indicates that both content validity and measurement properties of PRO instruments utilized in AS are preserved in the broad axSpA population.

Keywords: RAPID-axSpA; ankylosing spondylitis; anti-TNF therapy; axial spondyloarthritis; certolizumab pegol; non-radiographic axSpA; patient-reported outcomes; validation.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adult
  • Axis, Cervical Vertebra*
  • Communication
  • Female
  • Health Surveys
  • Humans
  • Male
  • Middle Aged
  • Outcome Assessment, Health Care*
  • Patient Outcome Assessment*
  • Physician-Patient Relations
  • Psychometrics*
  • Reproducibility of Results
  • Self Report
  • Spondylarthritis / psychology*
  • Spondylarthritis / therapy
  • Spondylitis, Ankylosing / psychology*
  • Spondylitis, Ankylosing / therapy