Objective: In AS there is no agreed definition of which aspects are important when describing functioning. This limits the possibility to classify, evaluate and investigate the consequences of the disease. This study aimed to achieve consensus among health professionals on which aspects of functioning are typical and relevant for AS patients using the International Classification of Functioning, Disability and Health (ICF) as reference.
Methods: An international Delphi study through e-mail was performed among different health professions. Answers to open questions on areas relevant for functioning in the first round were linked to ICF categories and analysed in the two following two rounds for the degree of consensus.
Results: Of the 267 experts invited, 126 agreed to participate and 74 participated in all rounds; 28 were rheumatologists, 6 rheumatology nurses, 24 physiotherapists, 2 occupational therapists, 4 psychologists, 8 rehabilitation physicians and 2 social workers. More than 80% agreement was reached on 141 ICF categories, of which 30 (21%) were part of Body functions; 27 (19%) of Body structures; 56 (40%) of Activities and Participation; and 28 (20%) of Environmental factors. In addition, two Personal factors-illness knowledge and coping-were agreed upon.
Conclusion: 141 ICF categories and two personal factors represent the reference of functioning in AS from the perspective of health professional. The largest number of categories concerned restrictions in activities. Also, the impact of AS on participation in life situations and the role of environmental factors were underscored. This broadens the view on functioning in AS and has implications for future research into functioning.