In 1997 and 1999, recommendations for outcome assessment of ankylosing spondylitis (or the minimum domains to be measured in trials or for clinical record keeping) were proposed by the Assessment of SpondyloArthritis international Society (ASAS)/OMERACT group. These recommendations was not primarily developed to comprehensively describe functioning of individuals with ankylosing spondylitis but rather to measure all aspects of outcome. Moreover, the selection of the ASAS/OMERACT domains did not include the perspective of non-rheumatologists or patients and it ignores the relationships among domains. To tackle these issues, the ICF Research Branch, the World Health Organisation (WHO) and the ASAS initiated an ICF Core Set development project to identify all aspects of "what to measure" when addressing the impact of ankylosing spondylitis on global functioning taking into account the perspectives of all parties. It was envisioned as the starting point for the global assessment of patients as well as for studying functioning and health and the development of new instruments.

In the preparatory phase of the project, a systematic literature review, a qualitative study, an expert survey and an empirical, cross-sectional study were conducted:

• A systematic literature review was performed to identify parameters and outcomes reported in studies published involving ankylosing spondylitis-specific instruments and functioning.
• A qualitative study (focus interviews) with 19 individuals with ankylosing spondylitis was conducted to identify the aspects of functioning and health which are important to individuals with ankylosing spondylitis
• A Delphi exercise was performed to gather the opinion of an international pool of 74 experts of different health professions regarding the most relevant and typical areas to be considered in individuals with ankylosing spondylitis.
• A empirical, cross-sectional study with 111 patients was performed ICF using the ICF checklist.

An international ICF consensus conference took place at the Swiss Paraplegic Research in Nottwil, Switzerland in September 2007. The aim of the conference was to establish the Comprehensive and Brief ICF Core Sets for patients with ankylosing spondylitis. Rheumatologists were selected from the members of Assessment of SpondyloArthritis international Society (ASAS). Other health professionals were recommended by ASAS members. Altogether 19 ankylosing spondylitis experts (13 rheumatologists, 3 physiotherapists, 1 specialist nurse, 1 occupational therapist and 1 psychologist) from 12 countries decided which ICF categories are to be included in the ICF Core Sets for ankylosing spondylitis following a multi-stage, interative decision-making and consensus process which integrated the results from the 4 preparatory studies.

In view of the clinical heterogeneity of ankylosing spondylitis, experts agreed that spinal and extra-spinal articular disease as well as uveitis were unique and typical manifestations of ankylosing spondylitis that they should be considered when defining the ICF Core Sets. At the consensus conference, 80 ICF categories were selected for inclusion in the Comprehensive ICF Core for ankylosing spondylitis. These categories can be taken into account when conducting a comprehensive, multidisciplinary assessment. Out of the 80 Comprehensive ICF Core Set categories, 19 ICF categories were selected as candidate categories for the Brief ICF Core for ankylosing spondylitis. The Brief ICF Core Set can be used in clinical studies.

These ICF Core Sets aim to represent the new reference for defining functioning in ankylosing spondylitis and facilitate clinicians' and researchers' efforts to incorporate a patient oriented, multilevel and comprehensive view on functioning with ankylosing spondylitis.

For more information, feel free to contact the ICF Research Branch (melissa.selb@paranet.ch).

• Comprehensive ICF Core Set for ankylosing spondylitis (download PDF)
• Brief ICF Core Set for ankylosing spondylitis (download PDF)