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The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part I): classification of paper patients by expert opinion including uncertainty appraisal
  1. M Rudwaleit1,
  2. R Landewé2,
  3. D van der Heijde3,
  4. J Listing4,
  5. J Brandt5,
  6. J Braun6,
  7. R Burgos-Vargas7,
  8. E Collantes-Estevez8,
  9. J Davis9,
  10. B Dijkmans10,
  11. M Dougados11,
  12. P Emery12,
  13. I E van der Horst-Bruinsma10,
  14. R Inman13,
  15. M A Khan14,
  16. M Leirisalo-Repo15,
  17. S van der Linden2,
  18. W P Maksymowych16,
  19. H Mielants17,
  20. I Olivieri18,
  21. R Sturrock19,
  22. K de Vlam20,
  23. J Sieper1,21
  1. 1
  2. 2
    Maastricht University Medical Center, Maastricht, The Netherlands
  3. 3
    Leiden University Medical Center, Leiden, The Netherlands
  4. 4
    Epidemiology Unit, German Rheumatism Research Centre, Berlin, Germany
  5. 5
    Rheumatology Private Practice, Berlin, Germany
  6. 6
    Rheumazentrum Ruhrgebiet, Herne and Ruhr-University, Bochum, Germany
  7. 7
    Hospital General de México and Universidad Nacional Autónoma de México, Mexico
  8. 8
    University of Córdoba, Spain
  9. 9
    University of California, San Francisco, USA
  10. 10
    VU University Medical Centre, Amsterdam, The Netherlands
  11. 11
    Hospital Cochin, Paris, France
  12. 12
    University of Leeds, Leeds, UK
  13. 13
    Toronto Western Hospital, Toronto, Canada
  14. 14
  15. 15
    Helsinki University Central Hospital, Helsinki, Finland
  16. 16
    University of Alberta, Edmonton, Canada
  17. 17
    University Hospital, Ghent, Belgium
  18. 18
    San Carlo Hospital, Potenza, Italy
  19. 19
    Glasgow Royal Infirmary, Glasgow, UK
  20. 20
    University Hospital, Leuven, Belgium
  21. 21
    German Rheumatism Research Centre, Berlin, Germany


Objective: Non-radiographic axial spondyloarthritis (SpA) is characterised by a lack of definitive radiographic sacroiliitis and is considered an early stage of ankylosing spondylitis. The objective of this study was to develop candidate classification criteria for axial SpA that include patients with but also without radiographic sacroiliitis.

Methods: Seventy-one patients with possible axial SpA, most of whom were lacking definite radiographic sacroiliitis, were reviewed as “paper patients” by 20 experts from the Assessment of SpondyloArthritis international Society (ASAS). Unequivocally classifiable patients were identified based on the aggregate expert opinion in conjunction with the expert-reported level of certainty of their judgement. Draft criteria for axial SpA were formulated and tested using classifiable patients.

Results: Active sacroiliitis on magnetic resonance imaging (MRI) (odds ratio 45, 95% CI 5.3 to 383; p<0.001) was strongly associated with the classification of axial SpA. The knowledge of MRI findings led to a change in the classification of 21.1% of patients. According to the first set of candidate criteria (sensitivity 97.1%; specificity 94.7%) a patient with chronic back pain is classified as axial SpA in the presence of sacroiliitis by MRI or x rays in conjunction with one SpA feature or, if sacroilitiis is absent, in the presence of at least three SpA features. In a second set of candidate criteria, inflammatory back pain is obligatory in the clinical arm (sensitivity 86.1%; specificity 94.7%).

Conclusion: The ASAS group has developed candidate criteria for the classification of axial SpA that include patients without radiographic sacroiliitis. The candidate criteria need to be validated in an independent international study.

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  • Competing interests: None.

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