[Assessments and outcome parameters for axial spondylarthritis in clinical studies and routine practice]

A standardized documentation of the clinical manifestation and patient-reported outcome (PRO) of patients with axial spondylarthritis (axSpA) is necessary in order to assess the disease with respect to disease activity and severity and to achieve the foundations for clinical decisions. The standardized documentation refers to domains such as disease activity, quality of life, functional capacity and ability to work but also to individual aspects, such as pain, arthritis and enthesitis. The domains as well as the individual aspects are mainly collected directly from PROs using a self-report questionnaire. An exception is the clinical examination of the inflammatory involvement of joints, entheses and the physical examination of spinal mobility. In interventional studies, status or response criteria are used to quantify changes. The lack of objective clinical criteria for documentation of inflammatory activity poses a particular challenge in axSpA, therefore, the PROs need to be interpreted critically taking objective disease parameters into consideration. Most instruments were developed in the 1990s in Bath, UK and in the last 15 years by the Assessments in Axial Spondylarthritis International Society (ASAS) for use in studies.