Monitoring ankylosing spondylitis: clinically useful markers and prediction of clinical outcomes.

Patient assessment in axial spondyloarthritis (axSpA) is multidimensional, and monitoring of disease activity, function and radiographic progression is complex. There is no simple 'gold standard' for measuring disease activity in all individual patients, as disease activity in axSpA is the sum of many different aspects and a complexity that cannot be represented by a single variable. Limited spinal mobility is a cardinal sign of ankylosing spondylitis and loss of spinal mobility has been reported to be a prognostic factor and most often evaluated with the Bath Ankylosing Spondylitis Functional Index. Imaging of the spine and assessment of safety aspects plays an important role in the monitoring of patients with axSpA. The timeframe for collecting information regarding disease activity, function and radiographic progression are recommended on an individual basis.